Design, Fabrication and Performance Analysis of Solar oVen

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DECLARATION

I hereby declare that this thesis, submitted to Universiti Malaysia Sabah as partial fulfillment of the requirements for the degree of Bachelor of Mechanical Engineering, has not been submitted to any other university for any degree. I also certify that the work described herein is entirely my own, except for quotations and summaries sources of which have been duly acknowledged.

This thesis may be made available within the university library and may be photocopied or loaned to other libraries for the purposes of consultation.

19 MAY 2014 MOHD FAZRIN BIN JAMMA@JAMAL

CERTIFIED BY

Dr. Nancy Julius Siambun

SUPERVISOR

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ACKNOWLEDGEMENT

Foremost, I would like express my sincere gratitude to my supervisor, Dr. Nancy Julius Siambun, for her excellent guidance, caring, patience help and support during completing this project. Her guidance helped me in all the time of research and writing of this thesis.

Next, my gratitude goes to Dr Tamber A. Tabet, my previous supervisor for his continuous support during completing my project 1. Without your supervising, I will not able to accomplish this research.

My sincere thanks also goes to my friend Nurzarinah Suharin, Kenny Vincent ,Jamaluddin Saparuddin who have been working together with me and help each other in the problems we faced. My research would not have been possible without their helps.

Last but not least, I would like to thank to my supportive parents and understanding family members that gives so much encouragement and help to finish this research.

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ABSTRACT

Malaysia has been regarded as country that has favorable climate for implementation of solar cooking. Solar cooking has been considered as simplest, safest, most convenient way to cook food. Therefore, in this research, a new solar oven has been designed, fabricated and experimentally examined. During the process, all factors such as material selection and design were considered accordingly in order to build finest solar oven. For comparison, a conventional solar box oven was also built. Both ovens were experimentally tested under no load condition, water as load and engine oil as load. By using thermocouple, temperature of load in both ovens was taken and from that calculation was able to be made. The difference in term of efficiency was regarded as improved efficiency. From all six experiments, it can conclude that a new design of solar oven has proved its ability in terms of thermal performance.

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ABSTRAK

Malaysia telah diklasifikasikan sebagai sebuah negara yang mempunya cuaca yang berpotensi bagi penggunaan cahaya matahari untuk tujuan memasak.Kaedah ini telah dianggap sebagai suatu alternatif yang dikira sebagai mudah, selamat dan tidak rumit. Oleh itu, melalui kajian ini, oven yang menggunakan cahaya matahari sebagai kaedah untuk memasak telah direka, dibina dan diuji melalui experimen. Semasa kajian dijalankan, faktor seperti pemilihan bahan dan rekaan telah diambilkira secara terperinci bagi menghasilkan oven yang baik. Bagi tujuan perbandingan, sebuah oven konvensional turut dibina. Semasa eksperimen dijalankan, kedua dua oven telah diuji dengan menggunakan air, minyak enjin dan akhirnya sekali tanpa sebarang beban. Suhu setiap medium telah diukur dengan menggunakan thermocouple dan berdasarkan suhu yang diambi,l penggiran telah dibuat. Perbezaan pada keberkesan oven telah diambil kira sebagai peningkatan keberkesanan daripada rekaan sebelumnya. Daripada keenam-enam eksperimen, kajian berjaya disimpulkan bahawa rekaan yang baru telah terbukti keberkesanannya daripada rekaan sebelumnya.

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CONTENTS

Page

DECLARATION i

ACKNOWLEDGEMENT ii

ABSTRACT iii

ABSTRAK iv

CONTENTS v

LIST OF TABLE ix

LIST OF FIGURES xii

LIST OF SYMBOL xvi

LIST OF ABBREVIATIONS xvii

CHAPTER 1 1

1.1 Introduction 1

1.2 Problem Statement 3

1.3 Objective 4

1.4 Scope of Work 4

CHAPTER 2 5

2.1 Introduction 5

2.2 Solar Oven Concept 5

2.2.1 Heat Gain 6

2.2.2 Heat Loss 7

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2.2.2.1 Conduction 8

2.2.2.2 Convection 8

2.2.2.3 Radiation 9

2.2.3 Heat Storage 9

2.3 Principle of Light Reflection in Solar Oven 9

2.4 Type of Solar Cooker 11

2.4.1 Direct Solar Cooker 12

2.4.1.1 Box Type Cookers 12

2.4.1.2 Concentrating Type Cookers 13

2.4.2 Indirect Solar Cookers 15

2.5 Parameter that Enhances the Performance of Solar Oven 17

2.5.1 Booster Mirror 18

2.5.2 Absorber Plate 19

2.5.3 Cooking Equipment and Cooking Chamber 20

2.5.4 Insulation 21

CHAPTER 3 23

3.1 Introduction 23

3.2 Project task 24

3.3 Selection of Criteria 24

3.3.1 Material Selection for Component 25

3.3.1.1 Main body 25

3.3.1.2 Insulator 25

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3.3.1.3 Cooking Pot 26

3.3.2 Design selection for component 27

3.3.2.1 Main Body 27

3.3.2.2 Reflector 27

3.3.2.3 Cooking Chamber 28

3.3.2.4 Cover of the Oven 28

3.4 Experimental Method and Procedure 29

3.4.1 Procedure 29

3.4 Calculation 30

CHAPTER 4 36

4.1 Overview of the Design 36

4.2 Design of Cooking Chamber 36

4.3 Design of Solar Reflector (Mirrors) 44

4.4 Structure Analysis of New Prototype (Prototype 2). 53

4.4.1 Mirror 1 ,2 and 5 55

4.4.2 Mirror 3 and 4 59

4.5 Design of Cooking Chamber for Prototype 1(Conventional Solar Box Oven) 62

4.5.1 Structure Analysis of Prototype 1 67

CHAPTER 5 70

5.1 Analysis of Results 70

5.2 Design and Prototype 70

5.2.1Material 70

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5.2.1.1 Main Body 71

5.2.1.2 Cooking Chamber 71

5.2.1.3Reflector 72

5.2.1.4 Insulator 73

5.3 Experimental Data and Analysis 73

5.3.1 Experiment 1 (Without Load, Duration 11:05am – 1:05pm) 75

5.3.2 Experiment 2 (Without Load, Duration 2:05pm – 4.05pm) 77

5.3.3 Experiment 3 (Water as Load, Duration 11:05am – 13:05pm) 79

5.3.4 Experiment 4 (Water as Load, Duration 2.05pm – 4:05pm) 81

5.3.5 Experiment 5 (Engine Oil as Load, Duration 11.05am – 1:05pm) 83

5.3.6 Experiment 6 (Engine Oil as Load, Duration 1.05pm – 4:05pm) 86

5.4 Effect of Additional Mirror and Insulator 89

5.4.1 Effect of Additional Mirror 89

5.4.2 Effect of Insulator 89

5.5 Energy Balance for New Prototype (Prototype 2) 89

CHAPTER 6 91

6.1 Overview 91

6.2 Conclusion 91

6.2 Future Work 92

REFERENCES 93

Appendix A 97

Appendix B 99

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Appendix C 101

Appendix D 104

Appendix E 106

Appendix F 108

Appendix G 111

Appendix H 114

Appendix J 117

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LIST OF TABLE

Table no. Page

Table 2.1 Characteristic of Four Commonly Used Absorber Materials 11

Table 3.1 Thermal Conductivity of Material 26

Table 3.2 Reflectivity of acrylic mirror 27

Table 3.3 Emissivity of Aluminum 28

Table 3.4 Characteristic of 3-mm single glazing glass 29

Table 5.1 Parameters and Condition for all 6 experiments 74

Table 5.2 Result of Experiment 1 75






Table A.1: Parameters of Load Used During Experiment 97

Table A.2: Capture Area of Prototype 2 and Prototype 1 98

Table A.3: Specification of material for glass 98

Table B.1: Specification of angle of mirrors for both prototypes 100

Table B.2: Specification of angle of mirrors for both prototypes 100

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Table B.3: Concentrate factor of respective experiment at given time 101

Table B.4: Time duration of each experiment 101

Table C.1 Highest Temperature Reached by the Cooking Chamber Surface 102

Table D.1 Highest Temperature Reached by the Cooking Chamber Surface 104

Table E.1 Time Taken by Load in Prototype 1 and Prototype 2 107

Table F.1 Time Taken by Load in Prototype 1 and Prototype 2 110

Table G.1 Time Taken by Load in Prototype 1 and Prototype 2 113

Table H.1 Time Taken by Load in Prototype 1 and Prototype 2 116

Table J.1 Thermal Conductivity of Aluminum and Alumina Wool 119

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LIST OF FIGURES

Figure No. Page

2.1 The Principle of Light Reflection 10

2.2 Different Types of Solar Oven 13

2.3 Example of Concentrating Solar Cooker 15

2.4 Example of Indirect Solar Cooker 17

2.5 Concept of Light Reflection in Concave Mirror 21

3.1 Flow of Research 24

3.2 Cooking Pot Used in this Project 26

4.1 Full Design of New Prototype (Prototype 2) using Solid Work 37

4.2 Isometric View of Cooking Chamber for New Prototype (Prototype 2) 37

using SolidWork

4.3 Top View of Cooking Chamber for New Prototype (Prototype 2) 38

using SolidWork

4.4 Side view of Cooking Chamber for Prototype 2 using SolidWork 39

4.5 Illustration of Light Reflection inside Cooking Chamber 42

4.6 Position of Cooking Pot inside Cooking Chamber in New Prototype 43

(Prototype 2)

4.7 Design of mirrors for New Prototype (Prototype 2) 45

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4.8 Mirror at the 1st side of New Prototype (Prototype 2) with Labels 46

4.9 Mirror at the 5th Side of New Prototype (Prototype 2) with Labels 48

4.10 Illustration of Triangle at the 5th Side of New Prototype (Prototype 2) 49

4.11 Mirror at the 3rd Side of New Prototype (Prototype 2) with Labels 51

4.12 Illustration of Triangle at the 3rd Side of New Prototype (Prototype 2) 52

4.13 Illustration of Force Exerted at the 2nd and 5th Side of New Prototype 55

(Prototype 2)

4.14 Illustration of Force Exerted at the 1st Side of New Prototype 55

(Prototype 2)

4.15 Isometric View of Bolts Used in New Prototype (Prototype 2) 57

4.16 Illustration of Force Exerted at the 3rd and 4th Side of New Prototype 59

(Prototype 2)

4.17 Top View of Bolts Used to Support Mirror at 3rd and 4th Side of New 61

Prototype (Prototype 2)

4.18 Design of Conventional Prototype (Prototype 1) 62

4.19 Top and Front View of Conventional Prototype (Prototype 1) 63

4.20 Illustration of Triangle to Find Optimum Mirror’s Angle of Conventional 65


4.21 Illustration of Force Exerted at the mirror of Conventional 67

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4.22 Bolts Used to Support Mirror of Conventional Prototype (Prototype 1) 68

5.1 Frame of Prototype 2 71

5.2 Cooking Chamber for Prototype 2 72

5.3 Mirrors Used for Prototype 2 72

5.4 Alumina Wool Placed in Prototype 2 73

5.5 Conventional Prototype (Prototype 1) and New Prototype (Prototype 2) 74

During Experiment.

5.6 Graph of Temperature for Conventional Prototype (Prototype 1) and 76

New Prototype (Prototype 2) in Experiment 1

5. 7 Graph of Temperature for Conventional Prototype (Prototype 1) and 78









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5.12 Graph of All Conducted Experiment 88

B.3 Illustration of Parameters to Calculate the Concentrate Factor 99

J.1 Thickness of Cooking Chamber from Side View 118

J.2 Thickness of Cooking Chamber from Side View 121

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LIST OF SYMBOL

Gravitational force

Thermal Conductivity m mass t Time

F Force

Density

Temperature

Shear stress

Absorptance C Specific heat capacity

Emissivity R Thermal resistance

U Overall heat transfer coefficient

Stefan-Boltzmann constant

Transmissivity

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LIST OF ABBREVIATIONS

vs. (versus) means against

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CHAPTER 1

INTRODUCTION

1.1 Introduction

Solar oven is a system that implements solar energy as a main power to supply heat

energy in order to cook raw food such as vegetables, meat, rice and so on. Solar

cooking can be considered as the simplest, safest, most convenient way to cook food

without any fuel consumption. In some country, for those people who cook over fires

fueled by collected firewood and spend much of their meager incomes on fuel, solar

cooking is more than a choice. With fact 783 million of people that have no direct

access in using gas cooker to heat water, solar oven might bring a new solution to

this matter. Furthermore, with expected increase in population, by 2030, food

demand is predicted to increase by 50% and 70% during 2050 (United Nations

International Year of Water Cooperation: Facts and Figures, 2003). Malaysia has

regarded as a country that has favorable climate that suitable for development of

solar energy. With abundant sunshine throughout the year, it has been reported that

average daily solar radiation in Malaysia can reach up to between 4.21-5.56kWh/m².

The solar radiation obtained annually is highest in August and November which is

estimated at 6.8 kWH/m², and the lowest is 0.61kWh/m² (Azhari et al., 2008). Thus,

there are a few places in eastern and northern region of Malaysia that have been

identified for their highest potential of solar energy implementation due to high solar

radiation throughout the year (Syahrul et al., 2012). Plus, previous research has

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supported the fact of Malaysia’s suitability for harnessing solar energy and developing

technology due to the availability of sunshine (Ali et al., 2009).

The differences of energy consumption in some countries caused some of the

solution are often not applicable. In some industrialized countries, energy

consumption is supplied by fossil fuels and nuclear. However for some places with

low humidity such as Africa, firewood is the main energy supply for the food cooking.

Due to ecological problems, somehow, firewood is hard to obtain and becomes

expensive in some regions. As a consequence, the continuous of fuel wood

consumption has caused exceeding upon its replacement, proportionally contributing

to deforestation, soil erosion and so on. Thus, the use of solar energy might

contribute much as an alternative energy supply since it does not have to be

replenished.

Solar cooker was first invented by Horase de Saussure, a Swiss naturalist. On

his first attempt, he managed to cook fruits in a primitive solar box cooker that

reached temperature of 190°F. Starting from that, many people started to use this

device at some places in India and China. However, since the cookers were not

affordable and too complicated designs, people have to continue to use the

traditional way of cooking. In 1950, the solar cooker started to evolve. Many top

engineers were hired to study different aspects of solar cooking designs. From that,

they came out with a conclusion that a proper constructed solar cooker not only can

cooked food thoroughly, but were quite easy to be used (Radabaugh, 1998).

There are three types of most common solar cooker which are heat-trap

boxes solar cooker, parabolic solar cooker and panel solar cookers. Heat box

cookers work by reflecting the sunlight into the box and trap the heat inside it.

Basically, this cooker cooks at moderate to high temperature and often

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accommodates with multiple pots. The second type of cooker is parabolic solar

cooker which has the ability to cook fast at high temperatures. However, this type of

cooker often need frequent adjustment and supervision, making it slightly

complicated compared to any other type of cookers. The last one is panel cookers.

Panel cookers incorporate elements of box and curved concentrator cookers. With

simple and relatively inexpensive, it becomes the most widely used combination solar

cooker.

Undeniable, to design a solar oven with high efficiency is quite impossible

since there are many uncontrollable factors that affect the performance. With a new

design of solar oven, this, probably might changes people’s perception toward this

device which indirectly solve the current problem encountered by the end user.

1.2 Problem Statement

Most of the end user of solar box cooker complained on the time consumption during

cooking the meal due to poor energy utilization. This poor energy utilization may be

caused by the design and material selection. As a consequence, people became less

interested towards solar cooker. Besides that, the concept of solar cooking has not

widely applied in Malaysia compared to other countries which has started using this

cooker. With a new design of solar oven, it may motivate people to practice solar

cooking.

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1.3 Objective

1. To develop a new design of solar oven.

2. To obtain a better performance of solar oven through proper material

selection and design.

3. To compare the heating performance between a new design of solar oven

with the conventional design solar oven.

1.4 Scope of Work

In order to achieve all objectives stated, there is few scope of work that needs to be

accomplished in this project. This research was started by doing a wide review on the

solar oven principle. From that, lots of idea was able to be pointed out and through

the study of literature, ideas of improving the solar oven system managed to be

decided.

Basically, material and design are the main key element in determining the

performance of solar oven. Thus, material was selected properly based on criteria

such as properties, availability and cost.

Meanwhile, in designing the prototype, factors such as dimension, endurance

and reliability was identified and evaluated in detail. Few designs were made and

from that the best design was selected. Evaluation was made based on method that

being used by previous researcher.

After finalizing everything, proposed design was fabricated accordingly. For

comparison, a conventional solar box oven was built. At the end phase of this

research, experiment was conducted to test and analyze the performance of both

prototype and efficiency was determined.

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CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

This section consists of discussions of solar oven with adequate knowledge to pursue

improvements on the factor that affecting the performance. Improvement of the

solar oven requires common knowledge from understanding concept, component

functions and utilizations and critical decision. Further details will be discussed in the

literature review as stated below.

2.2 Solar Oven Concept

Solar cooking defined as a concept that utilizes solar energy to cook food. Solar

cooking also aid some significant processes such as pasteurization and sterilization

(Cuce and Cuce, 2013 ). The history of solar cookers dates back to the 18th century.

Solar cooker is first introduced by a French-Swiss Physicist Horace de Saussure on his

first attempt to cook food by means of solar energy. He constructed a miniature

green house with 5 layers of glass boxes turned upside down on a black table and

reported cooking fruit (Cuce and Cuce, 2013). As time passes by, many countless

styles of solar cooker has been developed and continually improved by researchers

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and manufacturers. Solar has been regarded a clean energy generation that getting

more crucial day by day. Solar cookers are no longer presented as a total solution to

cooking problems but are being promoted as an add-on cooking device with specific

potential benefits and offering more choice and flexibility to consumers.

Implementation of solar cooker has found to bring many benefits to the environment

beside propose a better technique of energy utilization. Approximately, over one

third of the total primary energy consumption is used as the energy requirement for

cooking in many countries in the South East Asia (Muthusivagami et al., 2010).

Cooking is regarded as a major share of energy consumption in developing countries

(Pohekar et al., 2005). Besides that, solar cooking also has been well thought-out as

a key item to deal with environmental issues.

In the research made on the principle of cooking, the energy requirement is

at the peak during the sensible heating period. The energy required for a specific

cooking operation is not at a fixed value, depending with the cooking methods used.

During cooking, 20% of heat is spent in bringing food to boiling temperature, 35% is

spent in vaporization of water and 45% of heat is spent in convection losses from

cooking utensils (Muthusivagami et al., 2010). Basically, the performance of solar

cooker is controlled entirely by three main parameters which are heat gain, heat loss

and heat storage.

2.2.1 Heat Gain

In solar cooker, the heat is may initially generated by reflecting, absorbing or

concentrating the light from the sun (Saxena et al., 2011). In this case, mirror is

used as a reflector, collector for the absorbing process and parabolic disc as a

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concentrator. These factors have become the main role in determining the

performance of energy utilization.

Most of the radiant energy has a longer wavelength and thus inhibits them

from pass back out through the glass. Due to that, the reflected light is either can be

absorbed by other materials within the space or passes back out through the glass.

In solar cooker, heat gained can be controlled by the total of area for the glass faces

to the sun. It is because, the greater the area exposed, the greater the solar heat

gain.

At some circumstances, reflectors act a medium to bounce additional sunlight

through the glass, into the solar box. In a report made by researcher, the addition of

side mirror boosters can increase the output of solar Flat Plate Collector to permit

higher working temperatures and enhance the efficiency (Saxena et al., 2011).

2.2.2 Heat Loss

Heat transfer is thermal energy in transit due to a temperature difference and

become one of the most common physical phenomena in the world. Estimation of all

the worldwide energy utilization suffer more than 80% involve heat transfer

processes (Chen et al., 2013). According to the theory for thermal non-equilibrium, a

total system enclosing reactants and products is thermally isolated from its

surrounding and is in thermal non equilibrium (Chen et al., 2013). Heat loss is a

common natural problem that encountered by the user of solar cooker. Heat may

loss by conduction, conduction and radiation. In second law of thermodynamic

definite that heat always travels from high to low energy. The sunlight-to-heat

conversion occurs when photons (particles of light) moving around within light waves

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interact with molecules moving around in a substance. The energy exists in

electromagnetic rays made the solid or liquid to vibrate when they strike matter. As

they started to vibrate, apparently this will generate heat that will cook the food.

2.2.2.1 Conduction

Conduction can be defined as the diffusion of thermal energy and works by the

movement of thermal energy from regions of higher temperature to regions of lower

temperature. The transfer of thermal energy occurs in a material without bulk

motion of the material. In solar cooking, conduction has become one of obstacles

that frequently cause the reduction of thermal performance. For example, during

cooking the handle of a metal pan on a stove or fire becomes hot because of the

conduction. In the same way, heat generated inside the solar cooker lost when it

travels through the molecules of foil, glass, frame body to the outside of the box. It

is essential to place an insulator in order to reduce the total of heat loss through

conduction.

2.2.2.2 Convection

Convection is a process of thermal energy transfer between a solid and a moving

fluid. In convection, it can be reduced into two main phenomenon, forced convection

and free convection. Usually, forced convection occurs when a fluid is forced to flow.

Meanwhile in free convection, the bulk fluid motion is controlled by the buoyancy

effects (Ullmann et al., 2014). In solar cooking, free convection is occurred in which

molecules of air move in and out of the box through the cracks. As heated air

molecules within a solar box escape, it causes the cooler air from outside the box to

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enter. As a result, it reduces the total of heat inside the solar cooker and eventually

reduces the thermal performance of solar cooker.

2.2.2.3 Radiation

Radiation is the transfer of thermal energy between two objects through electro-

magnetic waves. Radiation does not have to use any solid or liquid medium in order

to take place. The concept of radiation is actually the main principle that been

applied in most type of enclosed solar cooker. Radiation takes place in a pot of solar

cooker as the pot is getting warmer. The heat waves generated by the pot usually

loss through the transparent glazing of the cooker.

2.2.3 Heat Storage

Heat storage is basically referred to the availability of material to store the heat.

Heat storage is very important as it regulates the performance of the cooker. In this

case, time taken to cook the food is measured as mark of performance. Heavy foods

tend to take longer time to be heated up due to additional heat storage capacity.

However, it enables the box to maintain heat inside the cooking chamber for a period

of time.

2.3 Principle of Light Reflection in Solar Oven

In order to harness the heat inside the cooking chamber, the concept of light

reflection is used as a working principle of solar oven. Euclid is credited for

developing the first and most sensible law of optics, called as the Law of Equal

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Angles (Beeson and Mayer, 2008). The law has stated that if a light gleams on a

surface at an angle, it will bounce off the surface at exactly the same angle. That

means, the angle of incident ray will be equal to the reflected ray. The following

figure shows the principle of light reflection.

Figure 2.1 The Principle of Light Reflection

Source: Beeson, S., & Mayer, J. . 2008. Patterns of light. Hardcover: Springer.

Retrieved from http://www.springer.com/978-0-387-75106-1

The reflection of light is often distinguished by the type of material. The

reflectivity affects so much in a solar cooker performance since the working principle

is dealing with the reflection of light. The thermal properties are usually separated

into two main parts, absorptivity and emissivity. Absorptivity is defined as a measure

of the material’s ability to absorb radiation while minimizing losses due to reflection.

Meanwhile, emissivity is a measure of the material’s ability to emit the collected solar

11

energy and is associated with a loss of solar heat (Cverna, 2002). Thus, the surface

that acts as a reflector should be low in absorptivity and high in emissivity.

Conversely, the absorber surface needs to be high in absorptivity with low in

emissivity. Table 2.1 shows the absorptivity and emissivity of four commonly used

absorber materials.

Table 2.1 Characteristic of Four Commonly Used Absorber Materials

source: Cverna, F. 2002. ASM Ready Reference: Thermal properties of metals. ASM

International.

Material Product Name and Manufacturer

Absorptivity Emissivity

1. Exposed and unfinished concrete

_ 0.65 0.87

2. Flat black latex paint (nonselective)

Various 0.96 0.87

3. Black chrome-coated copper foil, 24” wide strips, w/pressure-sensitive adhesive backing

Solar-L-Foil MTI Solar Inc, 220 Churchill Avenue Somerset, NJ Avenue Somerset, NJ O8873

(201) 246-1000

0.95 0.11

4. Aluminum (polished and unfinished)

_ 0.12 0.09

2.4 Type of Solar Cooker

Mainly, solar cooker can be divided into two main categories which are direct and

indirect type. Indirect type works in a way that collector is kept outside and the

cooking chamber is kept inside. This two main component are linked with

canalizations for the heat transfer (Harmim et al., 2013). Meanwhile, for direct solar

cooker, it is separated into two types which are reflector and box types. Reflector

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solar cooker works by concentrating the incident solar radiation on the focus where

the pot is placed. However, these types of solar cooker need a frequent adjustment

to optimize its operation. On the other hand, for box type solar cooker, it operates

by reflecting the collected solar radiation on plane reflectors.

2.4.1 Direct Solar Cooker

2.4.1.1 Box Type Cookers

Box type solar cooker is an insulated container with a multiple or single glass cover.

A box cooker can be defined as an enclosed box that heats up and seals in the heat.

In other words, solar box may also be referred to solar oven, where the same

concept of solar cooking is applied. This type of cooker is highly depending on the

greenhouse effect in which the transparent glazing permits the passage of shorter

wavelength solar radiation, but is opaque to most of the longer wavelength solar

radiation coming from relatively low temperature heated objects (Muthusivagami et

al., 2010). The cooking principle of this type of solar cooker is as follows, sunlight

enters the box through the top of the glass, the light waves strike the bottom and

thus making the cooking chamber hot. In order to hold the heat inside the cooker, a

double-walled insulated box will be used. Also, mirrors may be equipped on the solar

cooker to reflect additional solar radiation into the cooking chamber.

All the components play a major role to speed up the cooking time. The

advantages of box cooker have been recognized including the simplicity of its

construction and operations (Muthusivagami et al., 2010). Moreover, the cooker

claims to be more stable and able to keep food remains warm for a long period of

time compared to other type of solar cooker. On the adverse side, it can only reach

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low temperatures and may only be used in certain condition. The following figures

show solar oven with multiple and single reflector.

(a) Solar oven with multiple reflector (b) Conventional solar oven with

single reflector

Figure 2.2 Different Types of Solar Oven

source: Muthusivagami, R. ., Velraj, R., & Sethumadhavan, R. 2010. Solar cookers

with and without thermal storage-A Review. In Renewable and Sustainable Energy

Reviews 14 (2): 691–701

2.4.1.2 Concentrating Type Cookers

This type of solar cooker operates by placing the cooking pot on the focus of a

concentrating mirror. Basically, concentrating type solar cooker is working on two

axis tracking with a concentration ratio up to 50 and temperature up to 300° C

(Muthusivagami et al., 2010). Multifaceted mirrors, Fresnel lenses or parabolic

14

concentrators are the component that aids the modulus operands of this type of

cooker. In concentrating solar cooker type, it can be categorized into two types. For

the first type, the light is intense from above. This type of cooker obliges a dark

covered pot and a high temperature plastic bag. Within few hours of direct sunshine,

the meal can be ready without burning or drying out. For the second type, light is

penetrated from below. This can be regarded as the simplest type of concentrator

and quite easy to operate and to be built. The cooker mechanism is regulated

through a proper position between the cooking vessel and the tripod. The reason is

to concentrate the light and yet provide sufficient temperature for the cooking

purpose. This type of concentrating cooker is very popular due to sharper focus than

that of other types of reflectors but is very sensitive and still need a constant tracking

with the position of the sun. Although the parabolic reflector is a perfect design, it is

found difficult to be constructed. The following figure 2.3 show a concentrating solar

cooker.

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Figure 2.3 Example of Concentrating Solar Cooker

source: Yettou, F., Azoui, B., & Malek, A. 2013. Determination of Adjustment

Tracking Time in Two Types of Solar Cookers by Ray-Tracing Method. Presented at

the 4th International Conference on Power Engineering, Istanbul, Turkey: Energy

and Electrical Drive

2.4.2 Indirect Solar Cookers

Indirect solar cooker is a solar cooker system that physically displaces the heat

collector and pot in which a heat-transferring medium is used to convey the heat to

the cooking pot. Under this category, solar cooker with flat plat collector, evacuated

tube collector and concentrating type collector are common types of solar cooker that

have been widespread used in the community. The advantages of this type of

cooker have been seen noticeably due to the capability of fast cooking, large pot

volumes and the possibility of indoor cooking and heat flow control in the pots

(Muthusivagami et al., 2010). Nevertheless, there still few disadvantages of this

16

solar cooker including the non-removable pots that makes cleaning and dishing food

difficult.

Vacuum tube collector-bases solar cooker is another example of indirect type

solar cooker. It consists of a vacuum tube collector with integrated long heat pipes

directly leading to the oven plate. Several advantages have been determined such as

capability to reach high temperature, availability of working in shade or inside a

building due to spatial separation of collecting part and oven unit and unneeded of

sun tracking. An effective heat transfer system is required to accommodate this solar

cooker on ways to transfer the heat from the collector to the hot plate without a

marked decrease of temperature.

As a solution, heat pipes are highly recommended to be used for this purpose

due to the high thermal conductance which is extremely high and the heat transfer

between the evaporator and the condenser section is nearly isothermal

(Muthusivagami et al., 2010). In an experiment conducted by (Kumar et al., 2001),

it is observed that, system that applied the concept of Evacuated Tube Solar Collector

(ETSC) managed to supply heat at higher temperature (120°C) than normal flat plate

collector. ETSC is a system that formed by an evacuated tabular solar collector and a

pressure cooker and both units working together by heat exchanger. Figure 2.4

shows an example of indirect solar cooker.

17

Figure 2.4 Example of Indirect Solar Cooker

source: Klemens, S., Maria, E., & Vieira, d. . 2008. Characterization and design

methods of solar cookers. Solar Energy, 82, 157–163.

2.5 Parameter that Enhances the Performance of Solar Oven

Solar cooker or solar oven is highly dependent on the main components of the

cookers. After the 1980s, researcher started to focus on the optimization of geometry

parameters of solar oven since they have a dominant effect on performance (Cuce

and Cuce, 2013). The oven performance is basically controlled on how well the heat

lost is controlled through all the side of the oven. In this case, the heat lost may be

caused by radiation and conduction. Thus, it is important to maximize the top area

relative to the other sides. For solar oven, the parts that being considers are booster

mirror, absorber tray, cooking vessel, and insulation. Moreover, the characteristic

features of the reflective surfaces also play the main role if it is evaluated.

18

2.5.1 Booster Mirror

Previous research has been proved that booster mirrors can be utilized in order to

increase the efficiency of solar collectors since it provides extra solar radiation (Cuce

and Cuce, 2013). Mirrors also help to reduce the wind losses as wind will not be in

direct contact to the glazed surface. As a solution, an oven type-approached was

introduced as an alternate for collecting the solar energy that would drastically boost

the overall cooker efficiency (Saxena et al., 2011). Various curves were drawn which

proved the mirror boosters in addition has a good enhancement of efficiency of solar

collectors (Saxena et al., 2011). Supporting mirror boosters depends greatly upon

the incidence angle. However, at some point mirrors become less effective when the

solar incidence angle increases. Thus it is important to coordinate the incidence

angle and the position of sun accordingly.

At least two booster mirrors should be equipped in solar oven in order to

maximize the incoming solar radiation. In a research made by Ibrahim and Elreidy

on the performance of a solar cooker integrated with a plane booster mirror reflector

under the climatic conditions of Egypt, it shows that the position and the tilt angle of

the booster mirror are very important in order to maximize the sunlight

concentration. It was observed that, within 3 to 4 hours, a good meal for a family of

four can be ready (Cuce and Cuce, 2013). Meanwhile , in Indian institute of

Technology, Shukla and Gupta have made energy and energy analysis of a

concentrating solar cooker which is integrated with a linear parabolic concentrator of

concentration ratio of 20 (Shukla and Gupta, 2008). The experiments were

conducted in both summer and winter conditions and result had shown that the

average efficiency of their solar cooker was 14%. The main reason of the low

efficiency was because of heat losses due to 16 % of optical losses, 30% of

geometrical losses and 35 % of thermal losses. This shows that a proper utilization

19

of thermal is very important in order to form a good solar cooker. On the other

hand, an experiment that carried out by the Solar Thermal Application Research

Laboratory (STARlab) between December 2005 and April 2006 concluded that the

solar oven with external mirror panels had a higher efficiency compared to other

solar cooker that had not equipped with external mirrors (Shukla and Gupta, 2008).

2.5.2 Absorber Plate

Absorber plate is a plate that placed at the bottom of the pot in order to harness

better distribution and use of heat. Absorber tray of a box cooker is a simple FPC.

When solar radiation passes through a transparent cover (glazing) and impinges on

the black painted or coated absorber surface of high absorptivity, a large portion of

this energy is absorbed by the tray, transferred to the cooking vessels and cook the

food (Curlydock, 2007). Absorber tray enhances a good heat transfer to the food in

cooking pot. Theoretically, the nature and the color of the coating play the rate of

the heat absorption. Various colors coatings have been proposed over the solar

absorber in a ways to achieve better heat conductivity. As well as its materials,

copper, aluminum and steel are recommended to be used (Saxena et al., 2011). In a

research made by Harmim et al., solar box cooker or solar oven that integrated with

fins was approximately 7% more efficient than the conventional solar box cooker

(Harmim et al., 2010). On the other experiment conducted by Ozkaymak , the result

has revealed that absorber plate managed to reach 100°C during a period of 5 h,

apparently shows the possibility to cook most of the foods (Ozkaymak, 2007).

20

2.5.3 Cooking Equipment and Cooking Chamber

The role of cooking pots has been seen to be extremely important as it acts as a

medium that control the success of solar cooker. Cooking pots are generally defined

as items which air in conduction with the absorber tray (Cuce and Cuce, 2013). In

solar oven or solar box cooker, cylindrical shaped cooking chamber is recommended.

Black paint will be coated outside of the cooker in order to increase the conduction

rate of heat. In the experiment made by Joshi et al., solar cooking efficiency may be

increase from 10-25% to 60%. He added that the optimum heat flux should be in a

range of 16,200- 25,000 kcal/h m² where m² is the bottom surface area of the

cooking system (Joshi et al., 2012) . Besides that, the number of cooking pots in a

solar box cooker may vary depending on the quantity and the type of food (Saxena

et al., 2011). Performance may increase if the cooking vessel or cooking chamber is

designed in a concave shape instead of plain shape (Cuce and Cuce, 2013). This is

because of the reflected light is focus in a single point that may called as a focal

point. The focal point made the light focuses at the center of cooking chamber

eventually made the heat concentrated at the cooking area. The result has been

supported by the experiment done by Gaur et al. where the result had shown that a

concave shape of the lid of utensil reduces the time of cooking to 10-13% (Saxena et

al., 2011). Malhotra et al. have tested four solar ovens with different volumes and

fabricated for performance study. It was experimentally observed that the reduced

volume of a cooking chamber results in a good temperature rise and the results in

less cooking time as well as possibility of cooking most eatables (Saxena et al.,

2011). Figure 2.5 shows each ray of light is reflected to a focal point made the heat

concentrated at the center.

21

Figure 2.5 Concept of Light Reflection in Concave Mirror

source: Beeson, S., & Mayer, J. . 2008. Patterns of light. Hardcover: Springer.

Retrieved from http://www.springer.com/978-0-387-75106-1

2.5.4 Insulation

Efforts have been made to make changes to the internal geometry of the cooker box

and the shape of the absorber plate in order to improve the effectiveness of the solar

cooker (Harmim et al., 2013). It is important to consider every aspect that enhances

the performance of solar cooker. Thus, criteria that lead to a better result should be

properly inspect in order to get the best outcome. In this case, the outcome

accounts in term of thermal efficiency and the time taken to cook the meal. Thermal

insulation has found to be essential in achieving energy conservation. The

importance of thermal insulation has become significant on reducing energy

consumption, greenhouse gas emission and environmental impact (Stevanović,

2013). To reduce the total of heat loss from a solar oven or solar cooker, the walls

can be made thicker to increase the thermal resistance and then insulated with

22

material that have low thermal conductivities like glass- wool, foam, fiberglass,

corkboard, wool felt, cotton, sawdust, and paper which approximately has thermal

conductivities between 0.03 to 0.06 W/m/° C (Saxena et al., 2011). Besides that,

two plates of glass with a small gap between them also can be used as an insulator

to prevent heat from escaping back through the glass that eventually increase the

efficiency (Saxena et al., 2011).

23

CHAPTER 3

METHODOLOGY

3.1 Introduction

This section consists of review on the work done to accomplish this research. In

order to increase the performance of solar oven, a detailed review is done to achieve

the goal of this research. Basically, the performance of solar oven can be enhanced

by the controlling of four major parameters which are mirrors, cooking chamber,

cooking equipment and insulation. These components are marked as a key of

success of solar oven.

24

3.2 Project task

The flow showed in Figure 3.1 is the task of this project. Research on this solar oven

is done according to the following path.

Figure 3.1 Flow of Research

3.3 Selection of Criteria

Material and design are the main parameters that should be examined and properly

select in order to fabricate a good criterion of solar oven. In this section, the

specification of design and material of improved prototype are explained in detail.

Design prototype 1 and prototype 2

Experimentation /Testing

Data analysis

Setup of experiment

Fabrication of prototype 1 and prototype 2

Search for appropriate material

Data Collection

25

3.3.1 Material Selection for Component

This section consists of material selection for the main body and insulator of new

prototype.

3.3.1.1 Main body

The main frame body of this solar oven was built by using slotted angle bar. The slot

on the angle bar which is easy to be jointed has giving an advantage for fabrication

work. Due to malleable material characteristic, aluminum sheet metal has been

selected. The complex geometry of this solar oven has made aluminum become a

good choice in order to undergo work that involving on complex shaping process.

Next, the aluminum all inside the cooker was polished to increase the surface

reflectivity.

3.3.1.2 Insulator

As a mean to insulate the cooking chamber, alumina wool was used due to its

availability and low thermal conductivity. It was placed in all sides of the cooking

chamber. Thermal conductivity of material used for new prototype is shown in table

3.1 .

26

Table 3.1 Thermal Conductivity of Material

source: http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

Layer Material Thermal Conductivity

1 ,3 Aluminium

2 Alumina Wool

3.3.1.3 Cooking Pot

To enhance the total heat transfer into load, the surface area of cooking pot should

be black to increase the absorptivity of heat. However, due to some limitation,

cooking pot was not able to be fabricated. Thus, non-stick 16-cm maxim saucepan

made up from aluminum was used.

Figure 3.2 Cooking Pot Used in this Project

27

source: http://www.homebase.co.uk/en/homebaseuk/non-stick-aluminium-3-piece-

pan-set---grey192800?_$ja=tsid%3A21719%7Cprd%3A1609763&cm_mmc=Affiliate-

_-Cojun-_-TheFind.com-_-1609763

3.3.2 Design selection for component

Design selection covers in designing the main body, cooking chamber, and reflector.

3.3.2.1 Main Body

In this research, all the designing process involved was done by using SolidWork.

Previous study has proven that mirror boosters in addition has a good enhancement

of efficiency of solar collectors (Saxena et al., 2011). Thus, prototype was fabricated

with 5 sides for its reflector, yet increase total of heat reflection into the cooking

chamber of solar oven.

3.3.2.2 Reflector

Plane mirror is suggested to be used as medium to reflect the light into cooking

chamber.

Table 3.2 Reflectivity of acrylic mirror

source: http://www.engineeringtoolbox.com

Type Reflectivity,r

Acrylic mirror 0.9

28

Conventional mirror which made up from acrylic, was fabricated according to the

proposed design. Theoretically, reflectivity coefficient of conventional acrylic mirror is

shown in table 3.2.

3.3.2.3 Cooking Chamber

The cooking chamber was designed in a concave-shaped to concentrate more heat at

the center of cooking chamber based on law of reflection of concave mirror (Beeson

and Mayer, 2008). A perfect concave-shaped cooking chamber possibly might

increase total of heat concentrate on the surface of cooking pot. Emissivity of

aluminum used is shown in table 3.3.

Table 3.3 Emissivity of Aluminum

Source http://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html

Type Emissivity ,

Aluminum 0.9

3.3.2.4 Cover of the Oven

Single glazing glass is used and placed at the top surface of solar oven to keep the

air inside from losing to the surrounding. 3-mm single glazing glass was used due to

factor of availability and cost. Characteristic of this glass is shown in table 3.4.

29

Table 3.4 Characteristic of 3-mm single glazing glass

source: Cverna, F. 2002. ASM Ready Reference: Thermal properties of metals. ASM

International.

Type Transmissivity , Absorptivity,

3-mm single glazing glass 0.86 0.08

3.4 Experimental Method and Procedure

This part explain on the procedure and calculation used as mean of analysis for this

research.

3.4.1 Procedure

Basically, 3 tests were conducted to accomplish the analysis of this project. Every

test was carried out during morning section between 11.00 am to 1.00 pm and

evening section, 2.00 pm to 4.00 pm. Notably, experiment was only conducted if the

weather was favorable. During the experiment, temperature was measured by

means of thermocouple. For experiment 1 and 2, the temperature of cooking

chamber surfaces was measured. Meanwhile, for experiment 3, 4, 5 and 6, the focus

was on the temperature of load in each prototype.

Every 5 minutes, the reading of thermocouple for both prototypes were

taken. Angle of each mirror was adjusted and measured for every 20 minutes to

maintain the performance of prototype. Before initiating the experiment, surrounding

factors like, ambient temperature, wind, humidity and cloud cover was measured.

30

3.4 Calculation

Analysis in experiment 1 and 2 was done by making comparison between the highest

temperature reached between prototype 2 and prototype 1. The difference between

these temperatures was evaluated and marked as improved efficiency.

For experiment 2 and 3, analysis was focused on heat utilization between

heat input and heat output. Time taken by prototype 2 to reach the boiling point of

water was taken and used as reference in order to get the temperature in prototype

1. Total of energy input at given period in each prototype was calculated. Next, total

of energy used by load in both prototypes also evaluated. From that, ratio between

energy input and used was determined and become the efficiency. The difference

between the efficiency was evaluated and marked as improved efficiency.

For experiment 4 and 6, analysis was conducted by taking time taken by

prototype 1 to reach its stagnation temperature. Next the same temperature was

used as reference to get the time taken in prototype 2.Total of energy input at given

period in each prototype was calculated. Next, total of energy used by load in both

prototypes also evaluated. From that, ratio between energy input and used was

determined and become the efficiency. The difference between the efficiency was

evaluated and marked as improved efficiency.

To begin the analysis according to Michael (2008), total of power input was

determined by following formula 3.1.Formula is basically calculate total of input

power into the cooking chamber regardless the concentration factor made by

reflector

31

(3.1)

Next, the concentrate factor of each reflector for both prototypes was

calculated based on angle at desired time. To calculate, the following formula 3.2 is

used.

(3.2)

After the concentrate factor was obtained, power input with consideration of

concentrated factor was evaluated by using formula 3.3.

32

= (3.3)

Next, by using formula 3.4 total of power input into the cooking chamber at

given time was calculated.

= x t (3.4)

,

Theoretical value of energy needed by load to rise at given temperature was

evaluated by using formula 3.5.

(3.5)

, =

33

=

=

For experiment 1 and 2 the efficiency was evaluated by using formula 3.6

(Improved efficiency) 𝛈

(3.6)

, =

=

Meanwhile, for experiment 3,4,5 and 6 the efficiency was evaluated by using formula

3.7.

Efficiency of prototype , 𝛈=

(3.7)

, =

=

Improved efficiency= - (3.8)

, =

=

34

Energy balance in new prototype (prototype 2) was determined by using

formula 3.8 (A.Chengel & J.Ghafar ,2011). However due to lack of parameters, total

of heat loss caused by convection was not determined.

= + (3.9)

, =

=

=

=

=

Conduction occurs in cooking chamber was determined by using formula 3.9.

)]t (3.10)

, =

=

=

35

Meanwhile, radiation in cooking chamber was determined by using formula 3.10.

= A t (3.11)

, =

=

=

=

=

36

CHAPTER 4

DESIGN

4.1 Overview of the Design

In this project, design process covered in designing the cooking chamber, mirrors,

mirror’s support and main body. All these parts are designed based on factors that

have been review in chapter 2. Besides that, calculation is made to meet the

specification of good solar oven. The stress acting on the bolt used to support mirror

also calculated to make sure the joint is robust to support the weight of mirror.

4.2 Design of Cooking Chamber

Figure 4.1 shows the full design of new prototype (prototype 2). Basically, prototype

2 consists of 3 main parts which are main body, cooking chamber and mirrors.

Position of every mirror is shown as in figure 4.1. Mainly, prototype 2 is designed

based on ratio between area of mirror and captured solar area ( refer to figure 4.2).

Cost and availability are main factors that being considered during the planning

process.

37

Figure 4.1 Full Design of New Prototype(Prototype 2) Using Solid Work

Figure 4.2 Isometric View of Cooking Chamber for New Prototype

(Prototype 2) using SolidWork

38

Due to malleable properties of material, aluminum sheet is used to build the cooking

chamber of this cooker. Two layers of aluminum sheet are constructed whereby the

gap between these layers is reserved as a place for insulator (alumina wool).

Dimension of oven is as shown in figure 4.3.Total capture area for new prototype in

figure 4.2 is evaluated by using formula shown in 4.1.

(4.1)

Figure 4.3 Top View of Cooking Chamber for New Prototype (Prototype 2)

using SolidWork

39

Hence, from figure 4.3, given that Width,W= 0.265 m and length,L=

0.39m. Thus by using formula 4.1, total capture area of prototype 2 is

Cooking chamber of this oven consists of two main layers, which denoted as 1st layer

and 2nd layer.1st layer represents the main surface where the cooking pot is placed.

Meanwhile, 2nd layer is providing an additional layer in order to give section for

insulator.

Figure 4.4 Side view of Cooking Chamber for New Prototype (Prototype 2)

using SolidWork

Total surface area for the 1st layer of cooking chamber in new prototype

(refer to figure 4.3) is calculated by using formula 4.2.

40

(4.2)

Meanwhile, total surface area of the 2nd layer of cooking chamber in new

prototype is evaluated by using formula 4.3.

(4.3)

Given that, width= 0.265 m and length= 0.39m, r=

= 0.1325m. Thus, by

using formula 4.2 , total surface area for the 1st layer of cooking chamber is

41

Since the cooking chamber is half of a cylinder, thus

For the 2nd layer, given that, width= 0.375 m and length= 0.5m, r=

=

0.1875m. Thus, by using formula 4.3, total surface area for the 2nd layer of cooking

chamber is

Since the cooking chamber is half of a cylinder, thus

= 0.5891/2

= 0.1655 m²

42

To determine the focal point of light in concave shaped cooking chamber, the

principle of light reflection by concave mirror is used. It is essential to determine the

focal point so that, the curve of cooking chamber can be set up accordingly. Besides

that, it allows the spot of concentrated light to be known at once suggest the best

position for cooking pot to be placed.

Figure 4.5 Illustration of Light Reflection inside Cooking Chamber

To determine the focal point of the light reflection inside concaved shaped

cooking chamber (refer to figure 4.5) , formula 4.4 is used.

(4.4)

,

43

Given that, =60°, Since h is corresponding to radius of 1st layer of cooking

chamber, h is equal to 132.5mm. Thus, by using formula 4.4, the focal point of light

reflection is determined.

Figure 4.6 Position of Cooking Pot inside Cooking Chamber in New


44

By referring to figure 4.5, height of cooking pot from C to D is 90mm.

From calculation, the focal point of reflected light (60°) lies at distance of 76.49mm

from the surface of cooking chamber, it can be safely assumed that, light that lies on

the surface of concave shaped cooking chamber might be able to be reflected back

onto surface of cooking pot. It is important to maintain the relationship between f, h,

θ and so that ideal solar oven can be designed.

4.3 Design of Solar Reflector (Mirrors)

In order to design a good solar oven, optimal angle between the glazing and the

reflector must be regulated. To enhance the reflective performance, ratio of size

between window of cooking chamber and mirrors is kept at 1 or less. Otherwise,

there will be light that failed to be reflected into cooking chamber. Theoretically, the

optimal angle between the glazing and the reflector is determined by using formula

4.5 (Solar Oven Design, 2012).

= 90°+ [ x {-(b 4a) + (0.25 x √ (4.5)

To determine angle at , formula 4.6 is used.

= 180 – θ (4.6)

45

Hence, at given angle , and width, the optimum height from the top surface

of the oven is determined by using formula 4.7

(4.7)

As shown in figure 4.7 represents the dimension of mirrors used for new

prototype (prototype 2).

Figure 4.7 : (a)Design and Dimension of Mirror for side 1,2 and 5 for New

Prototype (Prototype 2) Using SolidWork (b) Design and Dimension of

Mirror for side 3 and 4 for New Prototype (Prototype 2) Using SolidWork.

All dimensions are in mm.

46

In figure 4.8, to obtain the optimum angle for the mirror at side 1 , formula

4.5 is used.

Figure 4.8 Mirror at the 1st side of New Prototype (Prototype 2) with

Labels

Given M=0.390m and L=0.369m, thus, by using formula 4.5 angle is determined.

√

= 90°+ [ x {-(0.369 4(0.390)) + (0.25 x √

= °

47

Next, angle at is determined by formula 4.6.

= 180 – θ (4.6)

= 180 – 120.60

= 59.4°

Finally, given that x= 0.054 m a=59.4 ,by using formula 4.7 the height is

determined.

Thus, mirror 1 should be placed 0.091m from the top surface of the oven.

48

In figure 4.9, to obtain the optimum angle for the mirror at side 2 and 5 ,

formula 4.5 is used.

Figure 4.9 Mirror at the 5th Side of New Prototype (Prototype 2) with

Labels

Given M=0.244m and L=0.265m, by using formula 4.5.

√

= 90°+ [ x {-(0.265 4(0.244)) + (0.25 x √

= °

49

Figure 4.10 Illustration of Triangle at the 5th Side of New Prototype

(Prototype 2)

Next, angle at in figure 4.10 is determined by using formula 4.6.

a= 180 – θ

a= 180 – 116.19

a= 63.81

50

Finally, given that x= 0.0128m a=63.1 ,by using formula 4.7 the height is

determined.

Since mirror 2 and 5 are identical to each other, thus, mirror 2 and 5 should be

placed 0.252m from the top surface of the oven.

In figure 4.11, to obtain the optimum angle for the mirror at side 1 , formula

4.5 is used.

51

Figure 4.11 Mirror at the 3rd Side of New Prototype (Prototype 2) with

Labels

Given M=0.214m and L=0.369m, by using formula 4.5.

√

= 90°+ [ x {-(0.369 4(0.214)) + (0.25 x √

= °

52

Figure 4.12 Illustration of Triangle at the 3rd Side of New Prototype

(Prototype 2)


a= 180 – 113.39

a= 180 – 113.39

a= 66.61°

Finally, given that x= 0.0153 m a=66.61 ,by using formula 4.7 the height

is determined.

53

Thus, mirror 3 and 4 should be placed 0.035m from the top surface of the oven.

4.4 Structure Analysis of New Prototype (Prototype 2).

In this section, structure analysis is done at bolts joint for all mirrors. Firstly, force

exerted caused by mirror is determined by using formula 4.1

= (4.8)

54

Next, after making assumption, area of each bolts is determined by using

formula 4.2.

=

(4.9)

Where, A= Area

D= Diameter of bolt

After that, shear stress for each bolt is determined by using formula 4.3.

(4.10)

55

4.4.1 Mirror 1 ,2 and 5

Figure 4.13 and figure 4.14 shows illustration of force exerted in 2nd and 5th side of

new prototype (prototype 2).

Figure 4.13 Illustration of Force Exerted at the 2nd and 5th Side of New


Figure 4.14 Illustration of Force Exerted at the 1st Side of New Prototype

(Prototype 2)

56

Assume that, mirror 1, mirror 2 and mirror 5 as shown in figure 4.13 and

figure 4.14 are 1kg each .

= Force at mirror 1

= Force at mirror 2

= Force at mirror 3

Due to same weight, thus,

Hence, by using formula 4.8 force exerted in each mirror is determined.

= (1)(9.81)

= 9.81N

= 9.81N

Next, figure 4.15 shows total bolts used to support for every mirror.

57

Figure 4.15 (a) Isometric View of Bolts Used to Support Mirror at 1st,2nd,

and 5th Side of New Prototype (Prototype 2) (b)Side View of Additional

Bolts Used to Support Mirror at 1st,2nd and 5th Side of New Prototype

(Prototype 2) (c) Side View of Additional Bolts Used to Support Mirror at

5th Side of New Prototype (Prototype 2) (d) Side View of Additional Bolts

Used to Support Mirror at 2nd Side of New Prototype (Prototype 2)

Mirror 1 is held by 4 bolts that has diameter of 0.013m. Thus, force is

divided by 4 in order to get force exerted on each bolt which results to 2.4525N. Area

of each bolt is determined by using formula 4.9.

=

=

58

= 1.327 x

Hence, by using formula 4.10, shear stress in each bolt is determined.

Thus, each bolt in at mirror 1 is, =

Meanwhile, for mirror 2 and mirror 5 , they are held by 5 bolts that has

diameter of 0.013m. Thus, by using formula 4.10, force is divided by 5 in order to

get force exerted on each bolt which results to 1.962N. Area of each bolt is

determined by using formula 4.9.

=

=

= 1.327 x

59

Hence, by using formula 4.11 shear stress is determined.

Thus, shear stress of each bolt at mirror 2 and mirror 5 is, =

4.4.2 Mirror 3 and 4

Figure 4.16 shows illustration of force exerted in 3th and 4th side of new prototype

(prototype 2).

Figure 4.16 Illustration of Force Exerted at the 3rd and 4th Side of New


60

Assume that, mirror 3 and mirror 4 are 0.5kg each .

= Force at mirror 3

= Force at mirror 4

Due to same weight, thus,

Hence, by using formula 4.8 force exerted in each mirror is determined.

= mg

= (0.5kg)(9.81)

= 4.905 N

= 4.905 N

61

Figure 4.17 Top View of Bolts Used to Support Mirror at 3rd and 4th Side of

New Prototype (Prototype 2)

Each mirror held by 5 bolts that has diameter of 0.013m. Thus, force is

divided by 5 in order to get force exerted on each bolt which results to 0.99N. Area


=

=

= 1.327 x


62

Thus, shear stress of each bolt at mirror 3 and mirror 4 is, =

4.5 Design of Cooking Chamber for Prototype 1(Conventional Solar Box Oven)

Figure 4.18 (a) Design of Conventional Prototype (Prototype 1) with label

by using SolidWork (b) Design of Mirror for Prototype 2 with Dimension.All

Dimension in mm.

63

Prototype 1 in figure 4.18 is designed based on criteria of conventional of solar box

oven that same in size approximately with total capture area of prototype 2. To

improve the performance, optimal angle between glazing and the reflector has been

determined by calculation. Due to limitation of budget, ratio between mirror and

capture area is not able to be fully adjusted. As a way out, the same size of mirror

that is used by prototype 2 was fabricated and installed.

Figure 4.19 (a) Top View of Conventional Prototype (Prototype 1) (b) Front

View of Prototype 1. All Dimension in mm.

For conventional prototype (prototype 1) (Figure 4.19), total capture area

is determined by using equation 4.11.

(4.11)

L

64

Given, Width= 0.319 m and length= 0.344m,by using formula 4.11 total

capture area of conventional prototype (prototype 1) is determined .

Area

Area

65

In figure 4.20, to obtain the optimum angle for the mirror of conventional

prototype ( prototype 1), formula 4.5 is used.

Figure 4.20 Illustration of Triangle to Find Optimum Mirror’s Angle of

Conventional Prototype (Prototype 1)

Given that M=0.244m and L=0.319m, by using formula 4.5 optimum

angle is determined.

√

= 90°+ [ x {-(0.319 4(0.244)) + (0.25 x √

= °

66


a= 180 – θ

a= 180 – 139.42

a= 40.6°

Finally, given that x= 0.054 m a=40.6 ,by using formula 4.7 the height is

determined.

Thus, mirror 1 should be placed 0.075m from the top surface of the oven.

67

4.5.1 Structure Analysis of Prototype 1

Figure 4.51 shows illustration of force exerted by mirror of conventional prototype

(prototype 1).

Figure 4.21 Illustration of Force Exerted at the mirror of Conventional


Assume that, the weight of mirror A is 1kg . Hence, by using formula 4.8

force exerted in each mirror is determined.

= Force at mirror A

= mg

= (1)(9.81)

= 9.81N

68

Figure 4.22 Bolts Used to Support Mirror of Conventional Prototype

(Prototype 1)

Mirror A is held by 6 bolts that has diameter of 0.013m. Thus, force is

divided by 4 in order to get force exerted on each bolt which results to 1.635N.Area


=

=

= 1.327 x


69

Thus, shear stress of each bolt at mirror A is, =

70

CHAPTER 5

RESULT AND DISCUSSION

5.1 Analysis of Results

In this section, design and result obtained will be discussed. Sets of data obtained

during the experiment have been used to analyze and determine the efficiency of

solar oven. Both data gained from prototype I and II are tabulated and graphs are

plotted. Results are wrapped up based on consideration of all factors that affecting

the performance of cooking.

5.2 Design and Prototype

This section covers on the material and design result. Further discussion is made for

new prototype (prototype 2).

5.2.1Material

During fabrication process, materials to construct both prototypes were selected

based on various factor like availability, cost and so on. Due to limitation of budget, it

is important to choose material that is low in cost but able to fulfill the desired

requirement.

71

5.2.1.1 Main Body

Main body of prototype 2 shown in figure 5.1 was constructed by the slotted angle

bar in order to ease the process of construction. By means of bolt and nuts,

measured slotted angle bar were joint together and prototype able to be built.

Figure 5.1 Frame of Prototype 2

5.2.1.2 Cooking Chamber

As shown in figure 5.2, to construct the cooking chamber, aluminum sheet has been

used due to properties of this material which is lighter and reflective. Besides that,

the material of aluminum which is malleable has made the shaping process become

easier. Special glue was being used to keep the aluminum sheet in shape.

72

Figure 5.2 Cooking Chamber for Prototype 2

5.2.1.3Reflector

As shown in figure 5.3, mirrors were used as mean to reflect the sunlight towards

cooking chamber. 5 mirrors were used to equip every side of this prototype. All

mirrors were fabricated according to the proposed design.

Figure 5.3 Mirrors Used for Prototype 2

73

5.2.1.4 Insulator

As shown in figure 5.4,to insulate the prototype , alumina wool was placed between

the layer’s gaps in order to reduce the total heat loss to surrounding. Alumina wool

that is theoretically low in thermal conductivity might provide better utilization of heat

inside the cooking chamber.

Figure 5.4 Alumina Wool Placed in Prototype 2

5.3 Experimental Data and Analysis

Three set of experiment were conducted under different conditions and load. Each

experiment was conducted twice per day for two hour from 11.05am – 1.05pm and

2.05pm to 4.05pm.

74

Table 5.1 Parameters and Condition for all 6 experiments

Table 5.1 shows parameters and condition used for all 6 experiments for

this research. Basically all experiments are set up exactly as shown in figure 5.5.

Figure 5.5 Conventional Prototype (Prototype 1) and New Prototype

(Prototype 2) During Experiment

Experiment Sample Ambient

temperature

Humidity Wind

speed

Cloud

cover

Time

1 No load 38.0° C 66% 5km/h 60% 11.05 AM

2 No load 32.8° C 63% 6km/h 75% 2.05 PM

3 250ml of

water

33.8° C 60% 6km/h 66% 11.05 AM

4 250ml of

water

32.8° C 69% 9km/h 73% 2.05 PM

5 250ml of oil 31.2° C 66% 6km/h 66% 11.05 AM

6 250ml of oil 33.7° C 55% 7km/h 75% 2.05 PM

75

5.3.1 Experiment 1 (Without Load, Duration 11:05am – 1:05pm)

Experiment 1 was conducted under no load condition. For 2 hours, between 11.05am

to 1.05pm both prototypes were left under sunlight exposure and both cooking

chamber’s temperature were measured by using thermocouple. From data obtained

(refer to table 5.2), the highest temperature for both prototypes were determined

and analyzed.

Table 5.2 Result of Experiment 1

Time interval (min) Temperature (°C)

(Cooking pot 1) (Cooking pot 2)

0 40.8 40.4

5 54.4 68.6

10 74.5 97.8

15 80.1 108.6

20 82.6 116.4

25 89.3 127.0

30 90.7 129.2

35 91.3 132.0

40 92.3 138.0

45 92.0 137.1

50 90.5 137.2

55 93.8 139.5

60 90.0 139.0

65 89.4 141.5

70 87.0 142.0

75 84.5 143.2

80 79.6 132.3

85 76.0 128.9

90 74.8 125.6

95 75.3 126.9

100 77.3 125.1

105 78.1 125.3

110 79.3 127.1

115 79.8 127.4

120 78.3 126.1

76

Figure 5.6 Graph of Temperature for Conventional Prototype (Prototype 1)

and New Prototype (Prototype 2) in Experiment 1

Graph in figure 5.6 shows tabulation of data between temperature for both

prototype 1 and 2 under no load condition. During the experiment, temperature of

both cooking chamber was measured. Under sunlight exposure, the highest

temperature gained by prototype 1 and 2 was 93.8°C and 143.2°C respectively. At

the beginning of the experiment, both prototypes’ temperature increased

continuously with their respective time. As they reached the peak temperature, both

systems became thermally equilibrium. After that, temperature became averagely

constant and reduced. The decreasing and increasing in temperature is probably

caused by unsteady weather. Under no load condition, the highest temperature

observed in prototype 2 was 143.2°C which was achieved within 75minutes.

Prototype 1 was not able to reach 100°C; however, the highest temperature

recorded was 93.8°C. From calculation (refer to appendix C), efficiency in term of

improved temperature made by prototype 2 over prototype 1 is 34.49%.

93.8

143.2

0

20

40

60

80

100

120

140

160

0 51

01

52

02

53

03

54

04

55

05

56

06

57

07

58

08

59

09

51

00

10

51

10

11

51

20

Tem

pe

ratu

re

Time

Graph of temprature vs time

Prototype 1

Prototype 2

77

5.3.2 Experiment 2 (Without Load, Duration 2:05pm – 4.05pm)

For experiment 2, the experimental method was conducted based on what had been

done during experiment 1. Experiment 2 was conducted from 2.05pm to 4.05pm, the

same day as experiment 1 .




0 40.4 40.8

5 63.6 73.5

10 75.5 89.9

15 80.7 100.7

20 80.2 106.2

25 81.0 112.2

30 82.0 115.7

35 84.7 119.0

40 88.0 119.7

45 91.0 120.7

50 88.2 125.5

55 89.2 127.0

60 88.4 123.0

65 83.8 121.1

70 82.5 120.8

75 80.9 117.8

80 81.2 119.6

85 80.0 117.4

90 76.8 115.7

95 75.6 114.5

100 74.3 113.6

105 78.9 116.7

110 79.2 116.9

115 81.0 118.4

120 82.0 121.1

78



In figure 5.7, it shows graph of temperature for both prototypes during

experiment 2.Experiment was conducted to determine the potential for both

prototype 1 and 2 under no load condition. During the experiment, both prototypes

were exposed under the sunlight and the temperature in each cooking chamber was

measured. From data obtained (refer to table 5.3), a graph is plotted as above. At

the beginning, the temperature was increasing continuously with respective to time.

After reaching peak temperature, temperature in both prototypes was not able to get

any higher. Due to unsteady weather, temperature of both prototypes were

increasing and decreasing randomly over the period of 120 minutes. From the

graph, the highest temperature obtained by prototype 1 is 91°C and 127°C for

prototype 2.The time taken for prototype 2 to reach its highest temperature was 55

minutes while 45 minutes for prototype 1. From calculation ( refer to appendix D),

91

127

0

20

40

60

80

100

120

140

0 10 20 30 40 50 60 70 80 90 100 110 120

Tem

pe

ratu

re

Time

Graph of temperature vs time

Prototype 1

Prototype 2

79

efficiency in term of improved temperature made by prototype 2 over prototype 1 is

28.35%.

5.3.3 Experiment 3 (Water as Load, Duration 11:05am – 13:05pm)

Experiment 3 was conducted to test the performance of prototype 2 and 1 under

load of 250ml water. During the experiment, water was selected in order to see the

prototype’s capability to boil the water. Experiment 3 was carried out within 2hours

between 11.05am to 1.05pm.



(Prototype 1) (Prototype 2)

0 44.9 44.5

5 46.3 59.6

10 49.6 66.8

15 53.2 75.0

20 56.2 82.3

25 59.0 89.2

30 60.1 91.5

35 62.0 93.1

40 63.0 97.2

45 63.6 98.5

50 65.0 100.0

55 65.1 100.3

60 65.3 100.1

65 65.7 101.2

70 65.6 101.1

75 65.7 100.8

80 65.9 100.5

85 65.8 100.1

90 66.5 100.5

95 67.1 100.9

100 67.4 100.7

105 67.3 100.5

110 67.2 100.4

115 67.3 100.4

120 67.1 100.0

80

For experiment 3, to analyze the data, time taken by prototype 2 in order to

reach 100°C was used as fixed variable. Yet again, the same time was used as a

guideline in prototype 1’s data in order to get desired temperature.



Figure 5.8 shows graph of temperature vs time for experiment 3 based on

result obtained (refer to table 5.4). Both prototype 1 and 2 show escalations in

temperature along the 120 minutes time of experiment. It can be safely assumed

that, temperature and time are directly proportional to each other. At the beginning

period of experiment, temperatures for both prototypes increased gradually. After

reaching the thermal equilibrium, the temperatures were maintained at certain level.

Under passive load of 250ml water, prototype 2 was able to reach water boiling

point,100°C within 50 minutes. Meanwhile, prototype 1 was not able to reach boiling

point of water. At the corresponding time of 50 minutes, water temperature inside

67.4

100.9

0

20

40

60

80

100

120

0 51

01

52

02

53

03

54

04

55

05

56

06

57

07

58

08

59

09

51

00

10

51

10

11

51

20

Tem

pe

ratu

re

Time


Prototype 1

Prototype 2

81

prototype 1 was 65.0°C. The highest water’s temperature recorded for prototype 2

was 100.9°C. Additional of 0.9°C is may be due to presence of impurities which

eventually made the boiling point of water higher from theoretical value. For

prototype 1, highest temperature recorded was 67.4°C. Theoretically, energy needed

by 250ml of water for prototype 2 to increase from 44.5 °C to 100°C is 57,831 . For

prototype 1, water acquires 20,944.2 of energy to increase from 44.9°C to 65.0°C.

Through calculation, prototype 2 managed to draw higher efficiency than prototype

1. From calculation ( refer to appendix E), it showed that, efficiency for both

prototype 1 and 2 is 41.63% and 47.39% respectively. Experiment 3 concludes that,

the efficiency of prototype 2 is 5.76% better than prototype 1.

5.3.4 Experiment 4 (Water as Load, Duration 2.05pm – 4:05pm)

In experiment 4, it had been conducted within period between 2.05pm to 4.00pm,

the same day as experiment 3 was conducted. Experimental method was exactly

what had been done in experiment 3.

Graph in figure 5.9 shows the plotted graph of experiment 4 based on data

obtained during the experiment (refer to table 5.5). During the 120 minutes duration

of experiment, both prototype 1 and 2 had shown constant increase of temperature.

After reaching the thermal equilibrium, both prototypes’ temperatures were

maintained at stagnation temperature. After minute 65, temperature of loads in both

prototypes started to drop until the end of experiment. Prototype 2 able to reach

100°C just 60 minutes after the experiment was initiated. At the corresponding time

of 60 minutes, the water temperature of prototype 1 was 57.4°C.

82




0 40.1 37.4

5 43.1 47.0

10 45.3 55.5

15 48.6 62.4

20 50.9 67.3

25 52.6 71.2

30 53.1 73.8

35 54.6 76.6

40 55.3 82.3

45 56.3 89.7

50 56.8 93.3

55 57.1 98.7

60 57.4 100.0

65 58.6 100.4

70 59.3 100.1

75 58.2 100.3

80 57.4 100.2

85 56.5 100.0

90 55.3 99.8

95 54.8 99.5

100 52.3 99.2

105 52.1 99.1

110 52.0 98.7

115 51.9 98.4

120 51.6 97.9



59.3

100.4

0

20

40

60

80

100

120

0 51

01

52

02

53

03

54

04

55

05

56

06

57

07

58

08

59

09

51

00

10

51

10

11

51

20

Tem

pe

ratu

re

Time


Prototype 1

Prototype 2

83

Results have shown that the performances of both ovens are slightly reduced

compared in experiment 1. This may be due to surrounding factors such as light

intensity, humidity, wind and so on. The highest load temperature recorded for

prototype 2 was 100.8°C. Additional 0.8°C is due to impurities that present inside the

water. Load in prototype 1 has recorded 59.3°C as its highest temperature. By

calculation (refer to appendix F), for prototype 2, of energy is required in

order to rise the water temperature from 37.4°C to 100°C. Meanwhile, for prototype

1, water needs of energy to increase from 40.9°C to 57.4°C. From

calculation prototype 2 was able to get higher efficiency which is 42.88% compared

to prototype 1, 27.68%. Efficiency for both prototypes was likely to reduce during

this period of time due to surrounding factors. In this experiment, prototype 2 is

leading the efficiency by 15.2%.

5.3.5 Experiment 5 (Engine Oil as Load, Duration 11.05am – 1:05pm)

Experiment 5 was carried out under load of 250ml engine oil. It was conducted to

observe the performance in term of time taken to reach stagnation temperature.

Due to high boiling point, engine oil has been used as load. In addition, it also

provided chances to observe highest possible temperature that might be reached by

prototype under given load. Method of analysis for this experiment was by taking the

time taken for load in prototype 1 once it reached its stagnation temperature. Next,

the same time was marked as guideline and from that temperature of load in

prototype 2 was determine.

84


Time interval Temperature (°C)


0 39.3 39.2

5 43.6 66.6

10 51.2 76.3

15 55.8 81.0

20 61.9 91.6

25 65.6 96.9

30 70.2 100.5

35 72.8 107.2

40 75.5 111.0

45 78.0 115.0

50 79.4 116.3

55 80.5 119.4

60 80.7 120.4

65 80.6 121.4

70 80.5 121.6

75 80.4 121.7

80 80.6 121.6

85 80.8 121.8

90 80.7 121.6

95 80.8 121.2

100 80.9 120.2

105 80.5 118.3

110 79.6 118.9

115 80.0 118.4

120 69.7 102.4

Figure 5.10 Graph of Temperature for Conventional Prototype (Prototype

1) and New Prototype (Prototype 2) in Experiment 5

80.9

121.8

0

20

40

60

80

100

120

140

0 51

01

52

02

53

03

54

04

55

05

56

06

57

07

58

08

59

09

51

00

10

51

10

11

51

20

Tem

pe

ratu

re

Time


Prototype 1

Prototype 2

85

Graph in figure 5.10 shows that tabulation of data between temperature and

time for both prototype 1 and 2 based on data obtained during the experiment (refer

to table 5.6).

Experiment 5 was carried out with using of 250ml oil to determine the

performance of oven. From the experiment, highest temperature for both prototype 1

and 2 can be finally determined. The highest temperature reached by prototype 1

and 2 were 80.9°C and 121.8°C respectively. From the beginning, both load’s

temperature escalated gradually until it reached its highest temperature. After that,

the temperatures were maintained which indicates that both oven were already

reached their thermal equilibrium. However, from 115 to 120 minutes of experiment,

result showed rapid decrease of temperature due to sudden unfavorable weather.

Prototype 1 managed to reach its stagnation temperature, 80.5°C within 55 minutes.

Conversely, to reach 81°C, only 15 minutes was needed by prototype 2. From that,

calculations were made based on ratio of time and temperature and from that

efficiency of both prototypes were determined. Theoretically from analysis (refer to

appendix G), load in prototype 1 requires of energy to increase from

39.3°C to 80.5°C. Meanwhile, for prototype 2, it needs of energy to increase

from 39.2°C to 81.0°C.Besides that calculations show prototype 2 was able to supply

more heat and taking less time to reach desired temperature compared to prototype

1. In term of heat utilization, calculation able to tell that prototype 2 has efficiency of

45.26% while 29.78% for prototype 1. Total of efficiency difference between both

prototypes is 15.48%

86

5.3.6 Experiment 6 (Engine Oil as Load, Duration 1.05pm – 4:05pm)

The same day as experiment 5 was conducted, experiment 6 was carried out starting

from 2.05pm until 4.05pm. Objective of experiment 5 was to test both prototypes

under load condition of 250ml engine oil. Experimental method was based on what

had been done during experiment 5.




0 44.1 44.6

5 54.9 53.4

10 60.0 62.8

15 63.9 73.1

20 65.9 91.6

25 67.8 96.6

30 68.0 100.4

35 68.2 104.7

40 68.6 106.3

45 70.5 109.0

50 71.2 110.1

55 72.2 110.8

60 72.3 111.5

65 72.5 112.4

70 72.6 112.4

75 72.4 111.3

80 72.2 110.8

85 72.0 110.2

90 72.0 110.0

95 71.7 109.6

100 70.8 105.7

105 70.4 104.6

110 70.1 103.8

115 69.8 102.5

120 69.7 102.4

87

Figure 5.11 Graph of Temperature for Conventional Prototype (Prototype

1) and New Prototype (Prototype 2) in Experiment 6

Graph in figure 5.11 shows temperature of 250ml of engine oil within period

of 120 minutes in both prototypes ( refer to table 5.7). At the beginning,

temperatures for both prototype 1 and 2 increased steadily. After reaching its highest

temperature, load was not able to go any higher due to thermal equilibrium. After

period of 95 minutes, temperatures for both loads (engine oil) dropped slowly due to

weather condition. In the experiment, the highest temperature reached for

prototype 1 and 2 were 72.8°C and 112.4°C respectively. At least 55 minutes were

needed by prototype 1 to reach its stagnation temperature. Stagnation temperature

for prototype 1 was 72°C. Meanwhile, prototype 2 was able to reach 73.1°C just 15

minutes after the experiment was initiated. By theoretical (refer to appendix H), total

of energy needed by prototype 1 in order to rise from 44.1°C to 72.2°C is .

Meanwhile, for prototype 2, to increase from 44.6°C to 73.1°C 11,400 of energy is

needed . From the experiment, data shows that, prototype 2 has higher efficiency

72.3

112.4

0

20

40

60

80

100

120

0 5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

10

0

10

5

11

0

11

5

12

0

Tem

pe

ratu

re

Time


Prototype 1

Prototype 2

88

compared to prototype 1.Under load of 250ml engine oil, prototype 2 managed to

reach 30.10% of efficiency 19.54% for prototype 1. To conclude, prototype 2 is

10.56% more efficient than prototype 1.

Figure 5.12 Graph of All Conducted Experiment

From all 6 experiments, by observation, it shows that, in term of performance,

prototype 2 has proved its higher efficiency compared to prototype 1. This may be

due to design and additional mirror booster that concentrate amount of heat inside

the cooking chamber. Besides that, result from graph in figure 5.12 shows that

experiment which is conducted within period of 11.05am to 1.05pm has tendency to

get better result compared that being conducted from 2.05pm to 4.05pm.

0

20

40

60

80

100

120

140

160

0 5

10

15

20

25

30

35

40

45

50

55

60

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75

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85

90

95

10

0

10

5

11

0

11

5

12

0

Tem

pe

ratu

re

Time


Experiment 1

Experiment 2

Experiment 3

Experiment 4

Experiment 5

Experiment 6

89

5.4 Effect of Additional Mirror and Insulator

5.4.1 Effect of Additional Mirror

From calculation, it showed that total of heat supplied by prototype 2 was

theoretically higher compared to prototype 1. Additional mirror has proved its ability

to concentrate more heat into the cooking chamber. In order to maximize the

potential of improved prototype ( prototype 2), mirrors were designed in optimum

position of angle. To maintain the performance, all five mirrors were adjusted

manually every 20 minutes. Calculation has theoretically proved that total of heat

supplied by prototype 2 is higher than prototype 1.

5.4.2 Effect of Insulator

Conduction, radiation and convection are all the factors that cause the heat loss. To

reduce the total of heat loss, alumina wools were placed all over the sides and

bottom of cooking chamber. Calculations have shown that the use of alumina wool

able to conserve heat from loss to the surroundings.

5.5 Energy Balance for New Prototype (Prototype 2)

In order to calculate the energy balance of prototype 2, heat transfer by conduction,

convection and radiation is determined. However, due to lack of parameter,

convection is not able to be evaluated. Thus, only conduction and convection are

able to be find. Energy balance is calculated based on data during experiment 3

.From calculation (refer to appendix J), total of heat loss by conduction and radiation

is 26,600.85 J and 25,032.68 J respectively. Meanwhile, total of energy input is

122,040 J. From theoretical calculation, energy needed by water to rise the

90

temperature from Heat loss by convection is not able to be calculated due to lack of

parameters.

91

CHAPTER 6

CONCLUSION AND FUTURE WORKS

6.1 Overview

This section covers on the conclusion made for this project. Recommendation is

provided in this part that might be used for further improvement.

6.2 Conclusion

Throughout the project, it shows that, in term of performance, prototype 2 has

verified its ability to attain better efficiency compared to prototype 1. Ideal design

and additional mirror booster has analytically prove its contribution in concentrating

amount of heat inside the cooking chamber. Based on various calculations, an

improved design was finalized and fabricated successfully. For comparison, a

conventional solar box cooker that approximately same in size was also fabricated. 6

experiments had been carried out and all data were analyzed. By analysis, it shows

that, experiment that conducted at early of the day has tendency to come with better

result outcome. Improved solar oven has proven to succeed for being able to keep

higher temperature throughout the day and eventually able to show its potential to

be implemented under tropical climate of Malaysia.

92

6.2 Future Work

For this project, the recommendations include on equipping each mirror with

automatic sun tracking system. During conduction of the experiment, each mirror

had to be adjusted manually for every 20 minutes in order to keep the high level of

reflected light. Therefore, by adding automatic sun tracking system, the mirror can

be adjusted significantly and accommodate the prototype itself efficiently at once in

maintaining its optimum performance. Besides that, to gain higher intensity of light,

additional mirror can be added along the interior sides of cooking chamber. It can be

concluded that the additional mirror helps to increase light supply to surface of

cooking pot. Due to limitation of budget, prototype 2 had been built with heavy

materials which make it less portable due to heavy weight. Thus, for it to become

portable, lighter material can be used to replace the angle bar which is used to build

the prototype.

93

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97

Appendix A

Calculation of Power Input for New Prototype (Prototype 2) and Conventional


Mass of Water and Oil

During the experiment, 250ml of water and 250ml engine oil were used as a load in order to test both prototypes. Properties of these load is shown in table A.1.To evaluate, mass of the

water and engine oil is determined by using formula A.1

=

(A.1)

Table A.1: Parameters of Load Used During Experiment

Type Volume (ml) Density (

) Specific heat

capacity (

)

Water 250ml 1000 4168

Engine Oil 250ml 880 2000

Thus, by using formula A.1 mass of water and oil is evaluated.

=

= 1000 x 0.25

=250 g

= 0.25 kg

And

=

= 800 x 0.25

=220 g

= 0.22 kg

Therefore, from calculation, 250ml of water is equivalent to 0.25kg of water while 250ml of engine oil is equivalent to 0.22kg of engine oil.

98

Calculation of Power input by Prototype 2 and Prototype 1

From previous chapter design, capture area for both prototype 2 and 1 were able to be determined (table A.2).

Table A.2: Capture Area of Prototype 2 and Prototype 1

Capture area of Prototype 2 0.1034 m²

Capture area of Prototype 1 0.1097 m²

Power input gained by both prototypes is initially determined by using following formula A.2.

= (A.2)

Table A.3: Specification of material for glass

Prototype

2 0.86 0.08

1 0.86 0.08

Table A.3 shows specification of material used in this research. By theoretical, constant solar radiation that entering earth’s atmosphere is equal to 1373 w/m² (A.Cengel &

J.Ghafar,2011). Since there is no actual value of solar radiation in UMS, Kota Kinabalu, we assume that solar radiation intensity is equal to this constant. Notably, level of radiation is

assumed to be the same in all experiments.By using formula A.2, power input is determined

for new prototype (prototype 2) and conventional prototype (prototype 1).

= 1373(0.86)(0.08)(0.1034)

= 9.767 W (W=

)

= 1373(0.86)(0.08)(0.1097)

= 10.36 W (W=

)

Therefore, without reflector, prototype 2 able to generate 9.767W of power

meanwhile prototype 1 is 10.36W

99

Appendix B

Calculation of Concentrate Factor by the Reflector of Prototype 2 and Prototype 1

To calculate the concentrate factor at given time, data of angle measured during conducting

the experiment is tabulated as in table B.1 ( 11.05 AM to 1.05 PM) and table B.2 (2.05PM to

4.05PM).As shown in figure B.1, concentrate factor is calculated by using formula B.1 . Assume that, all mirrors are parallel to top surface of oven.

Figure B.1 Illustration of Parameters to Calculate the Concentrate Factor

(B.1)

100

Table B.1: Specification of angle of mirrors for both prototypes between 11.05 AM

to 1.05PM

Angle of every mirror in both prototype (°)

Prototype 1 Prototype 2

Time Mirror 1 Mirror 1 Mirror 2 Mirror 3 Mirror 4 Mirror 5

0 102 102 111 136 136 111

20 108 108 113 133 133 113

40 116 116 113 133 133 113

60 120 120 110 130 130 110

80 116 116 113 126 126 113

100 108 108 113 124 124 113

120 102 102 111 122 122 111

Table B.2: Specification of angle of mirrors for both prototypes between 2.05 PM

to 4.05PM

Angle of every mirror in both prototype (°)

Prototype 1 Prototype 2

Time 1 1 2 3 4 5

0 90 90 110 130 130 110

20 85 85 108 132 132 108

40 80 80 100 132 132 100

60 75 75 100 132 132 100

80 70 70 110 132 132 110

100 70 70 110 132 132 110

120 70 70 110 132 132 110

Experiment 1

To analyze experiment 1 for prototype 2, all angles angle at minute 75 are taken and

calculated. Meanwhile, for prototype 1,all angles at minute 55 are chosen.All data are referred from table B.1.Thus, by using formula B.1 concentrate factor is calculated.

At minute 75

=

1+ [ (2)(0.9) (

)sin 110 + (2)(0.9) (

)sin 130 +(1)(0.9) (

)sin 120]

= 4.1805

And at minute 55

=

= 1+(1)(0.9)(

)sin 116

= 1.6187

Therefore, concentrate factor made by reflector in prototype 2 and 1 is 4.1805 and 1.6187 respectively.

101

Next,the same step is used to calculate concentrate factor for experiment 2,3,4,5 and 6 at

given duration of time.

Table B.3: Concentrate factor of respective experiment at given time

Time Concentrate factor

Prototype 1 Prototype 2 Prototype 1 Prototype 2

Experiment

2 Minute 45 Minute 55 1.6779 4.3446

3 Minute 50 Minute 50 1.6187 4.1647

4 Minute 60 Minute 60 1.6649 4.3268

5 Minute 55 Minute 15 1.6187 4.2029

6 Minute 55 Minute 15 1.6779 4.3083

Table B.4: Time duration of each experiment

Experiment Time duration

1,3,5 11.05 AM to 1.05PM

2,4,6 2.05 PM to 4.05PM

102

Appendix C

Calculation of Efficiency for (New Prototype) Prototype 2 and (Conventional Prototype) Prototype 1 in Experiment 1

By using formula C.3 ,efficiency for experiment 1 is calculated by taking the highest possible

temperature for both prototype 2 and 1.Time needed to rise until such temperature (refer to

table C.1) also being considered and taken. Basically analysis is initiated by using formula C.1 where the power input with consideration of concentrate factor is calculated. Next, after that,

by using formula C.2 total energy input in joule is calculated.

= (C.1)

= (C.2)

=

=


(C.3)

, =

=

Table C.1 Highest Temperature Reached by the Cooking Chamber Surface

Prototype Highest temperature of cooking chamber surface in prototype 1 and 2

Time taken

2 143.2 75 minutes

1 93.8 55 minutes

To calculate total power input reflected into cooking chamber, total power generated

without aid of reflector is multiplied by concentrate factor that already calculated in previous

section (Appendix B).

103

By using formula C.1, power input for prototype 2 is calculated.

= x G

= 9.767 W x 4.1805

= 40.83W

By using formula C.1, power input for prototype 1 is calculated.

= x G

= W x 1.6187

= W

Next, by using formula C.2 ,total power input for prototype 2 and 1 is multiplied by the time (refer to table C.1) to determine total of energy generated for given period of time.

Total power input for 75 minutes or 4500s for prototype 2

= x 4500

= 42.08 x 4500

= 189,360 J


= x 3300

= 17.06 x 3300

= 56,298 J

Improved efficiency of prototype 2 over prototype 1 is evaluated by using formula C.3.

𝛈

x 100%

𝛈

x 100%

𝛈 34.49%

104

Appendix D

Calculation of Efficiency for Prototype 1 and Prototype in Experiment 2

By using formula D.3, calculation of efficiency for experiment 2 is done by taking the highest possible temperature for both prototype 2 and 1.Time needed to rise until such temperature

also being considered and taken. Basically analysis is initiated by using formula D.1 where the power input with consideration of concentrate factor is calculated. Next, after that, by using

formula D.2 total energy input in joule is calculated.

= (D.1)

= (D.2)

=

=


(D.3)

, =

=

Table D.1 Highest Temperature Reached by the Cooking Chamber Surface

Prototype Highest temperature of load

in prototype 1 and 2

Time taken

2 127.0 55 minutes

1 91.0 45 minutes

To calculate total power input reflected into cooking chamber, total power generated without aid of reflector is multiplied by concentrate factor that already calculated in previous

section (Appendix B).

105

By using formula D.1, power input for prototype 2 is calculated.

= x G

= 9.767 W x 4.3446

= 42.43W

By using formula D.1, power input for prototype 2 is calculated.

= x

= W x 1.6779

= W

Next, by using formula D.2, total power input for prototype 2 and 1 is multiplied by the time (refer to table D.1)to determine total of energy generated for given period of time.


= x 3300

= 42.08 x 3300

= 138,864 J


= x 2700

= 17.06 x 2700

= 46,062 J

Improved efficiency of prototype 2 over prototype 1 is evaluated by using formula D.3.

𝛈

x 100%

𝛈

x 100%

𝛈 28.35%

106

Appendix E


The efficiency in experiment 3 is analyzed by using time as a fixed variable.The efficiency is

evaluated by using formula E.4 and E.5. When temperature in prototype 2 reached 100°C,

time taken to increase until such temperature is determined. Next, at correspond time, temperature of load in prototype 1 is observed and used in calculation by using formula E.1

,E.2 and E.3 .

= (E.1)

= (E.2)

=

=

(E.3)

, =

=

=


(E.4)

, =

=

Improved efficiency= - (E.5)

=

=

107

Table E.1 Time Taken by Load in Prototype 1 and Prototype 2

Time Temperature of load in

prototype 2

Temperature of load in

prototype 1

50 minutes 100 65.0

To calculate total power input reflected into cooking chamber, total power generated

without aid of reflector is multiplied by concentrate factor that already calculated in previous

section ( Appendix B).

By using formula E.1, power input for prototype 2 is calculated.

= x G

= 9.767 W x 4.1647

= 40.68W

By using formula E.1, power input for prototype 1 is calculated.

= x G

= W x 1.6187

=

Next, by using formula E.2, total power input for prototype 2 and 1 is multiplied by

the time( refer to table E.1) to determine total of energy generated for given period of time.


= x 3000

= 40.68 x 3000

= 122,040 J


= x 3000

= 16.77 x 3000

= 50,310 J

By theoretical, total energy needed to rise the water at given temperature for prototype 2 and prototype 1 is calculated by using formula E.3.

108

Theoretical total of energy needed to heat up water for prototype 2

(0.25)(4168)(100°C- 44.5 °C)

57,831


(0.25)(4168)(65°C- 44.9°C)

20,944.2

By using formula E.4, efficiency of prototype 1 and 2 is determined.

=

x 100%

= 41.63%

=

x 100%

= 47.39%

Improved efficiency is determined by using formula E.5.

Improved efficiency= -

Improved efficiency= 47.39% - 41.63%

Improved efficiency= %

109

Appendix F


Efficiency in experiment 4 is analyzed by using time as a fixed variable. The efficiency in experiment 4 is evaluated by using formula F.4 and F.5. When temperature in prototype 2

reached 100°C, time taken to increase until such temperature is determined. Next, at

correspond time, temperature of load in prototype 1 is observed and used in calculation by using formula F.1, F.2 and F.3.

= (F.1)

= (F.2)

=

=

(F.3)

, =

=

=


(F.4)

, =

=

Improved efficiency= - (F.5)

=

=

110

Table F.1 Time Taken by Load in Prototype 1 and Prototype 2

Time Temperature of load in

prototype 2

Temperature of load in

prototype 1

60 minutes 100 57.4

To calculate total power input reflected into cooking chamber, total power generated without aid of reflector is multiplied by concentrate factor that already calculated in previous

section (refer to appendix B).

By using formula F.1, power input for prototype 2 is calculated.

= x G

= 9.767 W x 4.3268

= 42.26W

By using formula F.1, power input for prototype 1 is calculated.

= x G

= W x 1.6649

=

Next, by using formula F.2, total power input for prototype 2 and 1 is multiplied by the time (refer to table F.1) to determine total of energy generated for given period of time.


= x 3600

= 42.26 x 3600

= 152,136 J


= x 3600

= 17.25 x 3600

= 62,100 J

111

By theoretical, total energy needed to rise the water at given temperature for prototype 2

and prototype 1 is calculated by using formula F.3.

(0.25)(4168)(100°C- 37.4°C)

65,229.2


(0.25)(4168)(57.4°C- 40.9°C)

17,193

By using formula F.4, efficiency of prototype 1 and 2 is determined.

=

x 100%

= 27.68%

=

x 100%

= 42.88%

Improved efficiency is determined by using formula F.5.




112

Appendix G


Efficiency in experiment 5 is analyzed by using temperature as a fixed variable. The Efficiency in experiment 4 is evaluated by using formula G.4 and G.5. When temperature in prototype 1

reached the stagnation temperature, the time taken to increase until such temperature is

determined. Next, same temperature marked as parameter to find time taken by prototype 2 to reach such temperature. Desired data is observed and used in calculation by using formula

G.1, G.2 and G.3.

= (G.1)

= (G.2)

=

=

(G.3)

, =

=

=


(G.4)

, =

=

Improved efficiency= - (G.5)

=

=

113

Table G.1 Time Taken by Load in Prototype 1 and Prototype 2

Temperature of load in prototype 2

and 1

Time needed for

prototype 1 to reach 80.5°C

Time needed for

prototype 2 to reach 81°C

80°C-81°C 55minutes 15minutes

To calculate total power input reflected into cooking chamber, total power generated without aid of reflector is multiplied by concentrate factor that already calculated in previous section (

Appendix B).

By using formula G.1, power input for prototype 2 is calculated.

= x G

= 9.767 W x 4.2029

= 41.05W

By using formula G.1, power input for prototype 1 is calculated.

= x G

= W x 1.6187

=

Next, by using formula G.2 total power input for prototype 2 and 1 is multiplied by the time(refer to table G.1) to determine total of energy generated for given period of time.


= x 900

= 41.05 x 900

= 36,945 J


= x 3300

= 16.77 x 3300

= 55,341 J

By theoretical, total energy needed to rise the engine oil at given temperature for prototype 2

and prototype 1 is calculated by using formula G.3.

114

(0.2)(2000)(81.0°C- 39.2°C)

16,720

Theoretical total of energy needed to heat up engine oil for prototype 1

(0.2)(2000)(80.5°C- 39.3°C)

16,480

By using formula G.4, efficiency of prototype 1 and 2 is determined.

=

x 100%

= 29.78%

=

x 100%

= 45.26%

Improved efficiency is determined by using formula G.5.


Improved efficiency= 45.26%-29.78%


115

Appendix H


Efficiency in experiment 6 is analyzed by using temperature as a fixed variable. Efficiency in experiment 4 is evaluated by using formula H.4 and H.5. When temperature in prototype 1

reached the stagnation temperature, the time taken to increase until such temperature is

determined. Next, same temperature marked as parameter to find time taken by prototype 2 to reach such temperature. Desired data is observed and used in calculation by using formula

H.1, H.2 and H.3.

= (H.1)

= (H.2)

=

=

(H.3)

, =

=

=


(H.4)

, =

=

Improved efficiency= - (H.5)

=

=

116

Table H.1 Time Taken by Load in Prototype 1 and Prototype 2

Temperature of load in prototype 2

and 1

Time needed for


Time needed for


73°C-72°C 55minutes 15minutes

To calculate total power input reflected into cooking chamber, total power generated without aid of reflector is multiplied by concentrate factor that already calculated in previous section

(Appendix B).

By using formula H.1, power input for prototype 2 is calculated.

= x G

= 9.767 W x 4.3083

= 42.08W

By using formula H.1, power input for prototype 1 is calculated.

= x G

= W x 1.6779

=

Next, by using formula H.2, total power input for prototype 2 and 1 is multiplied by the time (refer to table H.1) to determine total of energy generated for given period of time.


= x 900

= 42.08 x 900

= 37,872 J


= x 3300

= 17.43 x 3300

= 57,519 J

By theoretical, total energy needed to rise the engine oil at given temperature for prototype 2

and prototype 1 is calculated by using formula H.3.

117

(0.2)(2000)(73.1°C- 44.6°C)

11,400

Theoretical total of energy needed to heat up engine oil for prototype 1

(0.2)(2000)(72.2°C- 44.1°C)

11,240

By using formula H.4, efficiency of prototype 1 and 2 is determined.

=

x 100%

= 19.54%

=

x 100%

= 30.10%

Improved efficiency is determined by using formula H.5.



Improved efficiency=

118

Appendix J

Calculation for Energy Balance for Prototype 2

Heat Loss Due to Conduction

From all these parameters, rate of heat loss for every material is determined. Heat loss by conduction is determined by using formula J.1.

)]t (J.1)

, =

=

=

Figure J.1 Thickness of Cooking Chamber from Side View

Area of cooking chamber = x 0.375 x 0.5

= 0.589 m²

Dimension in figure J.1 is determined as below.

W=0.1325m

X=0.1335m

Y=0.1865m

Z=0.1875m

119

Table J.1 Thermal Conductivity of Aluminum and Alumina Wool

Layer Material Thermal Conductivity

1 ,3 Aluminum

2 Alumina Wool

By referring to table J.1, thermal resistance in circular material is determined as below.

=

(J.2)

Where, A= Outer diameter of material x

B= Inner diameter of material x

L= Length of object

K= Thermal conductivity of material x

Thus, by using formula J.2 thermal resistance is calculated for material used in cooking chamber.

= 100°C = 40°C

=

= 2.33x

=

= 5.32

=

= 2.36x

Next, thermal resistance of every material is added together. Total of heat loss is

obtained by dividing the temperature difference with rate of heat loss by materials shown in

formula J.3.

=

(J.3)

= Rate of heat loss in surface A

= Rate of heat loss in surface B

= Rate of heat loss in surface C

= Temperature inside the object

= Temperature outside the object

Hence,

120

=

= 9.40W ( for full circle)

Since cooking chamber is designed in half circle, thus, heat loss is divided by

=

= 4.70 W ( for half circle)

From experiment 3, to increase the water temperature to 100°C , prototype 2 need 3000s to heat it up.Assume that, wall of cooking chamber is the same as water temperature due to

thermal equilibrium.At the moment , temperature at the outside surface of cooking chamber is 50°C.Assume by average = 100°C, = 50°C. In order to obtain the

coefficient of heat loss in cooking chamber, formula J.4 is used.

) (J.4)

4.70 = )

= 0.3186 W/m².K

Thus, total of heat loss by the curved surface of cooking chamber,

)t

)(3000)

J

At the 2 of the side of cooking chamber, flat –square aluminum is used to insulate this part.By

measuring, the parameters stated as shown in figure J.2.

121

Figure J.2 Thickness of Cooking Chamber from Side View

From that coefficient of heat transfer by materials on the side of the cooking chamber is

determined by using formula J.5.

U=

(J.5)

Where, = Thickness of material

= Thermal conductivity of material

Hence

U=

U= 0.755 w/m².K

For both sides of cooking chamber, the area is calculated as below. Given radius is 0.1875m,

(

)

= 0.1104 m²

To calculate the total heat loss at the sides part of cooking chamber, formula J.1 is

used. Given that, = 100°C, = 50°C

122

)t

)(3000)

12,502.8 J

Therefore total heat loss due to conduction inside the cooking chamber is

= 14,098.05 J +12,502.8J

= 26,600.85 J

Heat loss due to radiation

To calculate the total loss due to radiation, formula 5.11 is used. Given that, = 100°C,

= 50°C , = 0.03, =(5.67 x W/m². ) =0.579 m²

= A t (J.6)

, =

=

=

=

=

=

Thus, by using formula J.6, heat loss due to radiation is determined.

= 100+273= 373K, = 40+273= 313K

= A t

=(5.67 x W/m². ) ( )

(0.579) (0.03) (3000)

= 25,032.68 J

Hence, overall total heat loss inside cooking chamber due to conduction and radiation

is evaluated by adding both the value.

123

= 25,032.68 J +26,600.85 J

= 51,633.53 J

To determine the energy balance of prototype 2, it is evaluated by using formula J.7.

= + (J.7)

, =

=

=

=

=

Hence, by using formula J.7, energy balance is evaluated.

= +

122,040 J= 57,831J+26,600.85+25,032.68+

= 12,575.47 J

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