DESIGN OF ADSORPTION REFRIGERATION SYSTEM ...

REVIEW - DESIGN OF ADSORPTION REFRIGERATION SYSTEM DRIVEN BY ENGINE

EXHAUST GAS FOR VEHICLES

VINEETH P. BABU1, R. VASANTH

2, VARUN BABU M K

3

1Post Graduate in Thermal Engineering, R.V.S College of Engineering And Technology,

Coimbatore, TamilNadu. 2Assistant Professor, Department of Mechanical Engineering, R.V.S College of Engineering And

Technology, Coimbatore, TamilNadu. 3Post Graduate in Thermal Engineering, R.V.S College of Engineering And Technology,

Coimbatore, TamilNadu.

Abstract

Heat generated cooling is a technique of refrigeration where the required cooling effect

is obtained by using heat energy as input. At present, the conventional cooling systems used in

automobiles are engine driven Vapour Compression Refrigeration (VCR) systems.

Some of the alternative heat generated cooling technologies suggested by researchers

in their work, which can replace engine driven systems are - solid adsorption cooling systems,

absorption cooling, Sterling cycle cooling, thermo acoustic refrigeration etc.

In this study, a comparison of vapour compression, vapour absorption and vapour

adsorption refrigeration systems is carried out. Literature review suggests that the adsorption refrigeration can be a suitable option

for mobile applications and for smaller capacities. The vapour adsorption system has a strong potential to be used as an alternative cooling system.

The estimated availability of exhaust gas energy suggests the capacity of cooling which can be greatly enhanced for a dedicated system. This thesis proposes an innovative, compact, and improved adsorption refrigeration

system design review, powered by engine exhaust heat.

1. Introduction

In India road transportation is a major mode of transport for goods over large distances using

trucks. In summer the atmospheric temperature in some parts of India touches 45oC. In such

a condition, the temperature inside the cabin of a transport truck can even exceed 50oC and it becomes extremely difficult to operate for the driver and the other operators. It may affect the driver’s health as well as may cause accidents. It affects the economy as transportation time increases. So there is a need for a cooling system to keep the temperature of the cabin in control. But presently the transport trucks in India and in most parts of the world are not provided with system for cabin cooling, as it is not economically viable with current technology.

At present, the conventional cooling systems used in automobiles are engine driven

Vapor Compression Refrigeration (VCR) systems. The cycle runs on engine power and

consumes around 10 to 15% of the total power produced by the engine and thereby increases

Journal of Information and Computational Science

Volume 9 Issue 12 - 2019

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the fuel consumption also by 10 to 15% and thus increases the per kilometer running cost [1, 2].

At present no cooling technology is commercially d e v e l o p e d , w h i c h can provide cooling

in a u t o m o b i l e s w i t h o u t a f f e c t i n g f u e l consumption. This is a major reason for

which the cabin cooling of the truck is avoided presently. Considering present energy crises

all over the world, it is very much necessary to explore new technologies and potential to

satisfy the need of society. At the same time, the efficient management of production and energy

conservation is also equally important. Therefore, a solution for cabin cooling of truck is

required without increasing fuel consumption. Cabin cooling of truck or air conditioning in

automobiles is just an application, there are many other applications where cooling can be

provided using energy available in waste heat. Therefore, from energy conservation point of

view also there is need for a technology which can provide solution of cabin cooling of trucks

using waste heat thereby saving a large amount of energy required for cooling and refrigeration

[2, 3].

1.1 Engine Exhaust Heat as a Source of Energy

From heat balance calculations it is clear that in automobiles, around 30% of the total heat energy supplied is going away with exhaust gases at very high temperature and around

30% of the total heat supplied is going away with cooling water. The breakup of energy consumption is shown in Fig. 1.1. In automobiles, the exhaust gas temperature is in the range of

around 200 to 600oC. A part of this heat energy can be used to produce the required refrigerating effect for cabin cooling. The literature in the field of refrigeration and air conditioning suggests that there are some systems, which run on heat to produce a cooling effect [3].

The trucks which are used for transport generally have engine capacities more than 100

kW. The heat required for operating a heat powered cooling system for capacity of 1 TR (3.5

kW), with a minimum Coefficient of Performance (COP) of 0.25 is 14 kW. The COP for a heat

generated cooling system is defined as the ratio of cooling effect to the heat supplied. The useful

available heat in engine exhaust is more than 50 kW, so it is clear that the required heat for

running a heat operated cooling system is very less as compared to the available heat in the

engine exhaust. Thus it can be stated that there is enough potential for the development of a

system that runs on heat rather than engine power for cabin cooling of the truck.

By solving the problem of cabin cooling of the truck, the truck driver will be provided

with better working conditions, which will result in a reduction in fatigue to the driver and

ultimately reduction of transportation time. And this can be achieved with a small initial cost

and small addition of weight to truck. As the system is using the heat available in exhaust

the temperature of exhaust gases going to atmosphere is reduced and thereby the reduction in

global warming can be an additional advantage. Ammonia is proposed to be the refrigerant which

is an environmentally friendly refrigerant so it may replace the Chlorofluorocarbon (CFC)

refrigerants, used in vapor compression refrigeration. The solution of the problem can further

be used as a model for development of cooling system operated by waste heat for other

applications. This system can solve many energy conservation problems and has the potential to

become a technology of the future [4].



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(a) Losses of energy along with exhaust and proposed cooling system

35%

30%

25%

20%

15%

10%

5%

0%

S

.

I

C

.

I

POWER COOLANTEXHAUSTRADIATION

(b) Losses of energy (heat balance)

Fig. 1.1 Breakup of energy supplied to the engine and proposed cooling system [40]



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1.2 Vapour Adsorption System as Alternative Technology

The cabin cooling of the truck can be achieved by using Vapour Compression

Refrigeration (VCR) system, Vapour Absorption Refrigeration (VAR) system or by using

Adsorption Refrigeration (AR) system. The dependence on engine power and the use of

Chlorofluorocarbon (CFC) refrigerants are the two main limitations of vapour compression

refrigeration systems, which make it an unacceptable solution for cabin cooling of the truck.

So there is a need for the development of a cooling system for truck which can operate

on the available engine exhaust heat. From literature review it is observed that vapour

absorption refrigeration and adsorption refrigeration are the two heat generated cooling

technologies, which have potential to become alternatives of vapour compression refrigeration.

The use of vapour absorption refrigeration or adsorption refrigeration system can solve the

problems associated with vapour compression refrigeration. A comparison of vapour

compression refrigeration, vapour absorption refrigeration with adsorption refrigeration is

presented in Table 1.1. The working principle and the main features of these three systems are

as follows:

The systems which have been used over the years for automobile air conditioning are

based on vapour compression refrigeration technology. Vapour compression refrigeration

system mainly comprises four principal components namely compressor, condenser, evaporator

and expansion valve. The working fluid which flows through these components is called

refrigerant. The refrigerant changes its phase from liquid to vapour and vapour to liquid and

thereby transfers heat to develop the required refrigerating effect. The working principle is

explained with the help of a schematic diagram as shown in Fig.1.2 (a). The compressor of the

vapour compression refrigeration system is driven by the power of the engine. Many

developments have taken in automobile air conditioning but most of them are concentrated

towards improvement in the system or system components. No alternative technology could

come up which can replace vapour compression refrigeration system for automobile air

conditioning.

Efforts to address the problem of dependence on engine power for air conditioning in

automobiles motivated researchers towards heat generated cooling systems. Vapour absorption

refrigeration system is one of the potential alternatives, which can replace the vapour

compression refrigeration. Vapour absorption refrigeration system is a refrigeration system,

where the compressor of the vapour compression refrigeration system is replaced by a

combination of an absorber and a generator. In vapour absorption refrigeration a combination of

liquid absorbent and refrigerant is used.



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Table 1.1 Comparison of vapour compression, vapour absorption and vapour adsorption refrigeration system

Vapour

Compression

Refrigeration (VCR)

system

Vapour Absorption

Refrigeration

(VAR) system

Adsorption

Refrigeratio

n (AR)

system 1. The VCR system is

driven by mechanical

power. 2.The refrigerants used

are not environment-

friendly 3. The refrigerants used in

VCR cause Ozone depletion 4. More number of

moving parts 5. COP is in the range of

2.5 to 3.5

6. The VCR systems are available in small sizes

7. The VCR system is

used in automobile air

conditioning 8. The overall weight

and size are suitable for

automobile

applications.

The VAR system is a heat driven system.

The commonly used

refrigerants are environment-

friendly. The refrigerants used in

VAR

does not cause Ozone

depletion Less number of moving

parts COP is less than that of

VCR system.

VAR is uneconomical

and difficult to build for less

than 10

TR cooling

capacity The VAR system is not suitable for automobile air conditioning

The overall weight and size is

not suitable for automobile

application

The AR system is

a heat driven

system. Commonly used

refrigerants are

environment-

friendly

The refrigerants used in VAR does not cause ODP

Less number of

moving parts COP is less than that of

VCR system. AR system can be

developed for

smaller cooling

capacities The AR system is

suitable for automobile

air conditioning The overall weight

and size is at par

with the VCR system



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(a) Vapour compression refrigeration system

(b) Vapour absorption refrigeration system

(c) Vapour adsorption refrigeration system

Fig. (1.2) Schematic working cycles of (a) Vapour compression, (b) Vapour absorption and (c) Vapour adsorption refrigeration system



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Vapour absorption refrigeration system is a heat operated system of refrigeration where

the generator is heated by using a heat source. When the generator is heated the refrigerant is

separated from the absorbent and is compressed in the generator. The compressed refrigerant

is passed to the condenser and the liquid absorbent is pumped back to the absorber to absorb

the refrigerant coming out from evaporator. The other principle components condenser,

evaporator and expansion valve are the same as those of the vapour compression

refrigeration system. The other processes of refrigeration are also the same as those in

vapour compression refrigeration [5]. The working principle of the system is explained in

the schematic diagram Fig.1.2 (b). The working of the system is explained in the schematic

diagram Fig. 1.2 (c) The adsorption refrigeration principle and the related theory of adsorption

are explained in the next chapter of the report.

2. Literature Review

Automobile air conditioning has a history of more than 70 years. The first automobile

air conditioning system was introduced by Packer in 1939 for car air conditioning. This air

conditioner was based on the principle of vapour compression refrigeration system. The

compressor of the vapour compression refrigeration system requires power and this power is

taken from the engine. As mentioned earlier the additional power required to run the system

increases fuel consumption. In the last 70 years, automobile air conditioning system has

undergone gradual and continual improvements in performance and efficiency as a result of

improvements in the individual components. But the principle technology (i.e. VCR) remains

the same, no significant advances took place in this long- existing technology over the decades

[7].

In the last few years with the increase in the fuel prices and depleting oil reserves the

energy resource availability problems are becoming more and more critical. Researchers and

scientists from different parts of the world have been focusing on the issue of energy

conservation. Automobile air conditioning is one such area where there is a potential for

energy conservation as there is a huge amount of energy available in engine exhaust, which

can be used for air conditioning. Many researchers in different parts of the world have been

working to develop a solution for automobile air conditioning using the energy from exhaust

gases. A review of this work is presented here in the following sections.

2.1 Heat generated cooling techniques

Heat generated cooling is a technique of refrigeration where the required cooling effect

is obtained using heat energy as input. Some of the alternative heat generated cooling

technologies suggested by researchers in their work, which can replace engine driven

systems are - solid adsorption cooling systems, absorption cooling, Stirling cycle cooling,

thermoacoustic refrigeration, active magnetic regenerator system, thermoelectric devices. The

comparison of various features and performance, the economical feasibilities and state of

research of these heat driven systems have been presented in the reviewed papers. The various

other issues associated with these technologies like material issues, advantages, and

shortcomings, applications have also been outlined in these papers [3, 8, and 9].



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Iyer et al. [9] in his work has presented an experimental study to explore the heat

potential of car engine exhaust gases to run a turbine of 1 kW. The power developed by the

Turbine has been used to run the compressor of vapour compression refrigeration system. A

cooling effect with temperature drop of 4oC has been achieved successfully. In this study

it was observed that a minimum engine speed required to run such system is more than 1400

rpm.In the last few decades vapour absorption refrigeration and solid adsorption refrigeration

are two heat generated cooling techniques that have attracted the attention of many researchers,

and a lot of research is in progress on these technologies. Considering the proposed work a

literature review in the field of automobile air conditioning has been carried out and, is

presented in the following sub- sections on vapour absorption and adsorption refrigeration

technologies and their applications.

2.2 Vapour Absorption Refrigeration System

Vapour absorption refrigeration (VAR) is one of the oldest refrigeration technologies.

French scientist Fero Dinonel developed the first absorption refrigeration machine in 1816.

Practically the vapour absorption cycle was first developed as Ammonia water system around

the start of the 20th century. VAR is a heat operated cooling system, which attracted the

attention of researchers for automobile air conditioning mainly from early 90s [10].

Researchers working in the field of refrigeration have been trying to explore the potential of

waste heat available in engine exhaust for operating absorption refrigeration system. Some

such efforts are briefly discussed below.

Mclaughlin [10] has done an exhaustive study of an alternative refrigeration system

for automobile applications. In this study absorption refrigeration has been considered as an

alternative technology of cooling. The design and modeling of the absorption refrigeration

system have been proposed with Li Br and water as working pair. In this study the engine

coolant water has been proposed as a source of heat. It has also been stated that the generator

temperature should be more than 93oC and the system can work at atmospheric temperature

less than 38°C.

Koehler et al. [11] studied the absorption refrigeration system using waste heat. In this

work a computer simulation has been presented for a prototype of an absorption system for

food transport truck refrigeration using engine exhaust heat. The Coefficient Of Performance

(COP) values of this non-optimized single-stage ammonia-water absorption cycle varied

between 0.23 to 0.3. In this work the result shows that the system can be realized for long-

distance driving on flat roads.

Manzella et al. [12] have presented an experimental study of an ammonia-water

absorption refrigeration system using engine exhaust. The experimental studies were

conducted on an absorption refrigerator stated that it took a time of 3 hours to reach a steady-

state temperature of 3 to13oC. It has been claimed in this paper that introduction of absorption

cooling system does not cause a significant pressure drop in the engine exhaust system. In the

experimental study a cooling effect of 14.9 to 18.4 W could be achieved with a very low COP

of around 0.05.



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Hilali and Soylemez [13] have presented an optimization analysis for estimating the

proper size of the absorption type automotive air conditioning system that uses waste exhaust

heat as input. In this paper a dynamic simulation of an ammonia-water absorption system has

been presented for 10.5 kW absorption system. This optimization analysis suggested the optimum effectiveness of the generator as 0.75 with a heat transfer area of 1.07 m2 at a COP of 0.5.

Venkatesan et al. [14] in their study have analyzed the possibility to drive a

vapour absorption system using exhaust gases from the engine for car air conditioning. In this

study the cooling load required to cool a car cabin up to a temperature of 20oC is calculated

as 0.714 TR. The minimum theoretical heat required to drive this system has been

calculated as 2.63 kW. The minimum useful heat available in the exhaust of a Honda City

car, considered for this study, has been calculated as 5.77 kW. Hence it was claimed that it is

possible to drive an absorption refrigeration system by car engine exhaust.

Salim [15] in his theoretical study and analysis has claimed that exhaust heat energy is

capable of powering and producing a cooling effect up to 1.2 tons of refrigeration using vapour

absorption cycle. The theoretical COP for absorption cycle has been obtained as 0.46. In his

study Ozone Depletion Potential (ODP) and the Global Warming Potential (GWP) of R-134a,

which is the current refrigerant employed in today’s vehicle has also been discussed. The

technical paper stated that Ozone Depletion Potential (ODP) of R-134a is zero but the GWP

of R-134a has been stated as

1300 as appose to the base that is carbon dioxide, that has GWP value of 1 by

definition.

Pongtornkulpanich et al. [16] in their work have presented an absorption cooling

system powered by solar energy. The system has been designed and experimented using solar

energy for a cooling capacity of 10 TR using LiBr/H2O. The collector area for an evacuated

tube solar collector and the cost analysis has been presented. It states that the initial cost of the

proposed system is higher but the system can become cost-effective if the operating costs are

compared.

Jacob et al. [17] in their technical paper investigated the development and testing of

single- stage solar or waste energy heated ammonia/water (NH3/H2O) diffusion- absorption

cooling machines (DACM). The designed cooling capacity of the cooling machine was 2.5 kW

at evaporator temperatures of -10°C. The pilot plants were gradually analyzed and stepwise

improved the second pilot plant now reaches a maximum cooling performance of 2 kW and

a coefficient of performance of 0.45.

The above literature on the absorption refrigeration shows that there is potential in the

engine exhaust to drive an absorption air conditioning system. A careful examination of the

work presented in the literature reviewed, reveals that very few of the proposed designs have

ever been built even as a prototype. The COPs obtained are very low, in some cases less than

0.1 with a cooling power less than 100 W. In some cases some experimentation has been done



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but that too in stationary conditions. The vapour absorption systems for automobile air

conditioning are not feasible from thermodynamic and manufacturing point of view for mobile

applications [18, 19]. Lambert and Jones [18] in their work have presented a review of heat

generated cooling techniques. In this study, they have presented the analysis of various

heat operated cooling systems and suggested the use of adsorption technology over the other

heat generated technologies, including VAR for automobile air conditioning application.

It is claimed that adsorption system is the best alternative for mobile air conditioning using

the heat of engine exhaust. A review of adsorption refrigeration system is presented in the

next section.

2.3 Vapour Adsorption Refrigeration

System

Adsorption refrigeration system with zero Ozone Depletion Potential (ODP)

refrigerants, powered by heat received increased attention from the last two decades. Unlike a

conventional refrigeration system driven mechanically by a compressor, an adsorption

refrigeration system is a heat-driven machine. Wang et al. [19] in their review paper have

presented a comparison of absorption and adsorption refrigeration technology. In this review

paper adsorption refrigeration has been claimed as a better alternative over absorption

refrigeration systems. It has been stated that adsorption refrigeration system can handle wide

range of temperatures from 50 to 500oC, whereas, in VAR the source temperature should be

at least 70oC and further the source temperature should not be more than 200oC. The study

also stated that absorption systems are not suitable for mobile conditions as the absorbent is

in liquid state, whereas in the adsorption system the adsorbent is in solid state. The review

paper further claimed that the adsorption system is much simpler than the absorption system.

Wang et al. [20] have studied the adsorption refrigeration technology and presented a

review of work done in the field of adsorption refrigeration. These technical papers have

studied properties of different refrigerants and adsorbents, commonly used working pairs for

adsorption cycles, characteristics, advantages and disadvantages of different adsorbents and

refrigerants. The selection of adsorbent refrigerant working pair based on application and

availability of heat has also been discussed. This paper has also presented the different

adsorption refrigeration cycles, different types of adsorption systems like physical

adsorption system, chemical adsorption system and a combination of both. This paper has

studied the deterioration of adsorption capacity in physical adsorption systems. The methods

for the measurement of adsorption capacity and the future research direction of adsorption

working pairs have also been analyzed.

Saha et al. [21] in the presented work have demonstrated dual-mode silica gel

water adsorption chillers design along with various temperature ranges. They obtained

optimum results for temperature range of 50 and 55oC. A comparison of COP has been

presented for three-stage mode and single-stage multiple modes. Simulation has been

presented and the COP is in the range of 0.2 and 0.45 respectively.

Wang and Oliveira [22] have presented the achievements in solid sorption refrigeration

prototypes, obtained since the interest in the sorption system was renewed at the end of 1970s.

The applications included ice making and air conditioning. In their work they have claimed

to obtain COP of 0.15 for solar application. In his review work the details of performance



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of adsorption system for different applications with their COP have been presented in a

tabular form. The COP is in the range of 0.3 to 0.6.

A report, presented by Christy and Toosi from Metrons Transportation Centre

California, have discussed the principle of adsorption refrigeration. The report suggests the

suitability of adsorption systems for vehicles. In that report the performance of vapour

compression refrigeration system and vapour adsorption refrigeration system has been

compared. This report presented an investigation of the feasibility of meeting the cooling

needs for commercial tractor-trailer refrigeration and transit bus air conditioning using engine

exhaust. The report states that the system size weight and heat balance are well within a reason

of a feasible design. In this study the adsorption refrigeration system has been designed for

activated carbon- ammonia and activated carbon - R134a as adsorbent refrigerant pairs. In this

work NH3 - activated carbon has been suggested as a suitable refrigerant - adsorbent pair for

automobile application [23].

Kong et al. [24] have presented an experimental investigation of the performance of a

micro combined, cooling heating and power system driven by a gas engine. In the described

system, a COP of 0.3 for refrigeration at 13oC has been obtained successfully. The suggested

system can supply electricity of 12 kW, the heat load of 28 kW and a cooling load of 9 kW

simultaneously.

Maggio et al. [25] have presented the results of a predictive two dimensional

mathematical model of an adsorption cooling machine consisting of a double consolidated

adsorbent bed with internal heat recovery. Internal heat recovery enhances the COP. It is

suggested that the adsorbent thickness should be limited to 2 to 3 mm for optimum results.

Lambert and Jones [26] in the second part of their work have demonstrated the design

of air conditioners for a car using heat of engine exhaust. The detailed design of the main

components of the proposed system has also been presented. The proposed system is an

adsorption system with two adsorbers heated by thermic fluid. The thermic fluid is proposed

to be heated by engine exhaust in a heat exchanger. It has been claimed that the overall weight

of the system is ~ 3.5 percent to the total vehicle weight, which is at par with the weight of

current vapour compression refrigeration systems. The specific cooling power (cooling power

per unit mass of adsorber) for the presented design has been claimed as 0.5 kW per kg of

adsorbing material with a cycle time of 900 s.

Tumainot et al. [27] have designed and developed a prototype of an adsorption

air conditioner using activated carbon-ammonia pair. In this work, a novel adsorber has been

designed and developed which, improves the heat transfer and has low thermal mass. The

prototype produced 2 kW cooling power with COP of 0.22, using engine cooling water. It has been studied the specific cooling power ranges from 0.65 to 0.80 kW/kg of adsorbing material for the developed system. The bed thickness of the adsorbing material (δad) of 4 mm and an eight-way valve has been suggested in this work.

Jiangzhou et al. [28] have presented a design of an adsorption air conditioner for locomotive driver cabin, powered by exhaust gases at 350 to 450oC. The cooling power and COP are 5 kW and 0.25 respectively. The cycle time of 1060 s with exhaust temperature of 450oC cooling air temperature of 40oC and chilled water temperature of 10oC is achieved. The specific cooling power of 164 to 200 W per kg has been obtained.

Salvatore et al. [29] have presented the design of an adsorption cooling system using

the zeolite water system. The overall volume and weight of the machine are 0.170 m3 and 60



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kg respectively. The experimental results obtained showed that the system delivered an average

cooling power 1 to 2.3 kW and a cooling COP 0.25 to 0.45, at a desorption temperature of

about 90oC. The system consists of a double-bed adsorber connected with an evaporator and

a condenser and driven by energy coming from the engine coolant.

Abdullah et al. [30] in their work have presented the various techniques of production

of activated carbon and the possibility to use Pam oil-based activated carbon for

adsorption refrigeration. The paper also discusses the need for change from the existing

technology of vapour compression refrigeration. It has been studied that the adsorption

refrigeration technology can satisfy the norms set by Montreal Protocol. Some researchers have

been concentrated on the modeling of adsorption refrigeration systems. COP and the specific

cooling power which are the most important parameters of adsorption systems can be evaluated

from these models. [31, 32]

Deng et al. [33] have presented a review of thermally activated cooling technologies

for combined cooling, heating and power systems. The difficulties and problems associated

with adsorption systems have been discussed in this paper. It has been stated that there are

three main problems in adsorption refrigeration technology, one is the low thermal

conductivity of the adsorbent; the second is the relatively low cycle mass of the working pair,

which means that the mass of refrigerant adsorbed and desorbed between adsorption phase

and desorption phase, is low; the third is the effective utilization of heat. These problems lead

to low COP (0.4 to 0.5) and a large volume and mass of the system. The innovative methods

suggested in the reviewed papers to make it a practical solution are, additives in adsorber

bed, use of suction pump with adsorber, finned absorber tubes, etc. The summary of

literature review is as follows:

The literature review suggests that a lot of work has been carried out to find a solution

for automobile air conditioning using heat of engine exhaust. Many heats generated cooling

techniques are available with distinctive features. Vapour absorption and adsorption

refrigeration are the two potential technologies. The absorption refrigeration is a technique

that is well developed and is suitable in the case of stationary application and for higher

capacities. The adsorption refrigeration can be a suitable option for mobile applications and

for smaller capacities. The vapour adsorption system has a strong potential to be used as an

alternative cooling system. From literature review it is also clear that sufficient background

is available to develop this technology to propose it as a solution for cabin cooling of truck

using engine exhaust.

In the literature review in the field of adsorption refrigeration, many adsorbents and

refrigerants have been suggested. The various adsorbents which have been used for adsorption

refrigeration include activated carbon, silica gel, zeolites. The various refrigerants which have

been mainly used for adsorption system are water, ammonia, and methanol. The adsorbent

refrigerant combination mainly used is activated carbon ammonia, activated carbon- methanol

and silica gel- water. The adsorbent refrigerant combination for engine exhaust heated system

used by the researchers was activated carbon and ammonia. The adsorption system studied in

the literature review gave a specific cooling power in the range 500 to 800 W per kg of

adsorbent. The COP of the presented system is in the range of 0.2 to 0.5. The adsorption

systems studied in the literature uses minimum 6 to 8 valves and hence complex in operation.



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3. Conclusion

This thesis proposes an innovative, compact, and improved adsorption refrigeration

system design, powered by engine exhaust heat. The system, which has been developed during

the course of the presented research work, makes the following contributions in the field of

adsorption refrigeration technology and automobile air conditioning using engine exhaust.

1. An innovative adsorption refrigeration system powered by heat with minimum of two

control valves is being developed by using superconductivity materials for the

manufacturing of valves and also by changing the design parameters. This is analysed

using Computational Fluid Dynamics.

2. An adsorption heat exchanger, which is compact approximately by 20% from the

existing systems is developed.

3. More heat transfer area is achieved by changing the following parameters of the valve - the diameter, pitch values and inclination of the position of valves.

4. An environment friendly cooling system has been designed that does not rely on engine

power, and thus helps in reducing resulting pollution as well as global warming. The

Global Warming Potential (GWP) of ammonia is zero.

5. A cooling system has been developed that does not use CFC refrigerant, and thus protect ozone layers over the atmosphere.

6. The designed system minimizes the chances of refrigerant leakages, which is a major

problem associated with ammonia adsorption refrigeration system. A system has been

developed with the external surfaces of the valve arrangement passing with cooling fluids

to minimize the heat input in the system thereby reducing the leakage of the system.

7. The developed adsorption system design provides platform for further development of

adsorption refrigeration technology and for waste heat operated cooling systems. The

research work for truck cabin cooling is one amongst the many such possible applications

of developed technology.

3.1 Scope for future work

Adsorption refrigeration is an emerging technology and can replace vapor compression

refrigeration and vapor absorption refrigeration research work can further be carried out to

develop this technology further and present it as a potential alternative. Waste heat potential

can be tapped and can assist for energy conservation.

1. The system design has been presented for a cooling capacity of 1 TR. The system can be

developed and tested on a 100 kW engine to verify its performance with automatic valves

and water as secondary refrigerant. And also fitting the system on trucks, paramedical

vehicles etc. can be considered.

2. The proposed system can operate with multiple heat sources like solar energy or other

waste heat sources. Such systems can be developed and tested.

3. Research can be done with other working pairs of adsorbent and refrigerant like R 134a and

activated carbon, methanol and activated carbon etc. and their performances can be compared.



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References

[1] Alam S., “A proposed model for utilizing exhaust heat to run automobile air-

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http://www.kazuli.com/vapour-compression-cycle.html

http://www.bestinnovativesource.com/vapour-absorption-cycle.html

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