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International Journal of Mechanical Engineering and Technology (IJMET)

Volume 8, Issue 12, December 2017, pp. 160–172, Article ID: IJMET_08_12_017

Available online at http://iaeme.com/Home/issue/IJMET?Volume=8&Issue=12

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

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ANALYSIS AND FABRICATION OF HEAT PIPE

AND THERMOSYPHON

M Sandeep

Research Scholar, K L University, Vijayawada, Andhra Pradesh, India

A.Abinay

Asst. Professor, ACE Engineering College, Hyderabad, Telangana, India

Dr P.Jamaleswara Kumar

Associate Professor, K L University, Guntur, Andhra Pradesh, India

ABSTRACT:

Effective thermal conductivity of a heat pipe wick structure filled with a working

fluid is measured. A simple evaluation method using a heating rod is described and

the value of effective thermal conductivity is obtained by comparing the numerical

results with the experimental ones. Full numerical simulation of heat pipes was

performed for heat pipe under various operating conditions with water as working

fluid. Two and three-dimensional models were developed assuming a laminar

incompressible vapor core. Finally, a homogenous multiphase model referred to as

volume of fluid modeling (VOF) was developed for simulation of a Heat pipe. A simple

thermosyphon was fabricated. The thermal response time of a thermosyphon in

comparison to a copper rod was observed. The response time and temperature profile

along thermosyphon was measured. The effective thermal conductivity of it was

calculated in a procedure like the heat pipe. Then the thermal conductivities of heat

pipe and thermosyphon were compared. Using PRO-E/CATIA software we try to

evaluate the design of the respective heat pipe. Later, we try to analyze the 3-D

incompressible flow. The methodology of the project is to design the heat pipe system

to carry out an analysis of the same using mechanical software based on the design

and analysis of the heat pipe will be modeled.

Keywords: volume of fluid (VOF) modeling; thermosyphon; PRO-E; analysis;

Cite this Article: M Sandeep, A.Abinay and Dr P.Jamaleswara Kumar, Analysis and

Fabrication of Heat Pipe and Thermosyphon, International Journal of Mechanical

Engineering and Technology 8(12), 2017, pp. 160–172.

http://iaeme.com/Home/issue/IJMET?Volume=8&Issue=12

M Sandeep, A.Abinay and Dr P.Jamaleswara Kumar


1. INTRODUCTION

Capillary-driven two-phase systems offer significant advantages over traditional single-phase

systems. With the typically increased thermal capacity associated with the phase change of a

working fluid, considerably smaller mass flow rates are required to transport equivalent

amounts than in single-phase liquid or gas systems for a given temperature range. Moreover,

heat transfer coefficients of two-phase systems are much greater than in single-phase flows

and result in enhanced heat transfer. Lower mass flow rates and enhanced thermal

characteristics provide the benefits of smaller system size (and weight) while providing

increased performance. The thermal capacity of a single-phase system depends on the

temperature change of the working fluid; thus, a large temperature gradient or a high mass

flow rate is required to transfer a large amount of heat. However, a two-phase system can

provide essentially isothermal operation regardless of variations in the heat load. Additionally,

single phase systems require the use of mechanical pumps and fans to circulate the working

fluid, while capillary-driven two-phase systems have no external power requirements, which

make such systems more reliable and free of vibration. The best known capillary-driven two-

phase system is the heat pipe, where a schematic of a conventional heat pipe is shown in

Figure 1.

Figure 1 Typical heat pipe construction and operation

The concept of the heat pipe was first presented by Gaugler (1944) and Trefethen (1962),

but was not widely publicized until an independent development by Grover et al. (1964) at the

Los Alamos Scientific Laboratories. Heat pipes are passive devices that transport heat from a

heat source (evaporator) to a heat sink (condenser) over relatively long distances via the latent

heat of vaporization of a working fluid. As shown, a heat pipe generally has three sections: an

evaporator section, an adiabatic (or transport) section, and a condenser section. The major

components of a heat pipe are a sealed container, a wick structure, and a working fluid. The

wick structure is placed on the inner surface of the heat pipe wall and is saturated with the

liquid working fluid and provides the structure to develop the capillary action for liquid

returning from the condenser to the evaporator section. With evaporator heat addition, the

working fluid is evaporated as it absorbs an amount of heat equivalent to the latent heat of

vaporization, while in the condenser section; the working fluid vapor is condensed. The mass

addition in the vapor core of the evaporator section and mass rejection in the condenser end

results in a pressure gradient along the vapor channel which drives the corresponding vapor

flow. Return of the liquid to the evaporator from the condenser is provided by the wick

structure.

Analysis and Fabrication of Heat Pipe and Thermosyphon


Due to the two-phase characteristics, the heat pipe is ideal for transferring heat over long

distances with a very small temperature drop and for creating a nearly isothermal surface for

temperature stabilization. As the working fluid operates in a thermodynamic saturated state,

heat is transported using the latent heat of vaporization instead of sensible heat or conduction

where the heat pipe then operates in a nearly isothermal condition. This nearly isothermal

condition offers benefits of transporting copious amounts of heat efficiently, decreasing the

overall heat transfer area and saving system weight. The amount of heat that can be

transported using latent heat is typically several orders of magnitude greater than transported

by sensible heat for a geometrically equivalent system. Additionally, no mechanical pumping

systems are required due to the capillary-driven working fluid. Given the wide range of

operating temperatures for working fluids, the high efficiencies, the low relative weights, and

the absence of external pumps in heat pipes, these systems are attractive options in a wide

range of heat transfer applications.

Table 1 Heat Pipe working fluids

Working fluid Triple pint(K) Critical point (K) Useful range(K)

Oxygen 54.3 154.8 55-154

Nitrogen 63.1 126.2 65-125

Ethane 89.9 305.5 100-305

Butane 134.8 425,0 260-350

Methanol 175.2 513.2 273-503

Toluene 178.1 593.9 275-473

Acetone 180.0 508.2 250-475

Ammonia 195.5 405.6 200-405

Mercury 234.3 1763 280-1070

Water 273.2 647.3 273-643

Potassium 336.4 2250 400-1800

Sodium 371.0 2500 400-1500

Lithium 453.7 3800 500-2100

Silver 1234 7500 1600-2400

Gravity assisted heat pipes or wickless heat pipes are highly efficient heat transfer devices

often referred to us as thermal super conductors or thermal short circuits. The efficient

thermal conductivity of thermosyphon exceeds that of copper 200-500 times [1]. A two phase

closed thermosyphon is a passive heat transfer device containing the working fluid in closed

container. It is used to transport a large amount of heat at a high rate with small temperature

difference between the sink and source. This is achieved by making use of the highly efficient

thermal transport process of evaporation and condensation. The thermal performance of two

phase closed thermosyphon (TPCT) has been extensively studied for a long period of time.

The behavior of TPCT filled with water, ammonia, toluene and conventional refrigerants like

R11 and R12 in a steady state situation are well known and numerous experimental and

analytical works are available in the literature [2-8]. The use of refrigerants as working fluids

is easy for certain applications because they work with positive work.

The literature survey revealed that the many of the research work deals with the TPCT

filled conventional refrigerants like R11, R12 and R22. However, knowledge of thermal

performance of TPCT filled with alternate refrigerant is of great importance since the

conventional refrigerants are banned due to their potential to deplete the ozone layer. Very

few investigations are made to study the thermal behavior of TPCT filled withR134a, which



is considered as an eco- friendly refrigerant and a generally accepted substitute for R11 and

R12.

Payakaruket. al, studied experimentally the effect of dimensionless numbers (Bond

numbers, Froude numbers, Weber numbers and Kutateladze numbers) on heat transfer

characteristics of an inclined thermosyphons. Copper thermosyphons withR22, R123, R134a,

ethanol and water as the working fluids are employed to predict heat transfer characteristics of

an inclined closed two phase thermosyphon at normal conditions. The effect of thermosyphon

inner diameter, fill ratio, aspect ratio and inclination angle is also studied.

Faghri et. al, reported the performance of a thermosyphon filled withR134a. They

concluded that the heat flux transferred increased with high coolant mass flow rates, high fill

ratios and greater temperature difference between bath and condenser in this experimental

work, the evaporator was immersed in a water bath to maintain constant temperature on

evaporator side. This type of TPCT can be termed as temperature controlled thermosyphon.

Abou- Ziyan et al. has investigated the effect of vibration on thermosyphon filled with

R134a. They found that minor or no effect is experienced with R134a below the boiling limit and

enhancement up to 250% existed above the boiling point.

The evaporator section of a thermosyphon covered with a heater to supply the required

flux can be termed as flux controlled thermosyphons. The experimental studies of a flux

controlled thermosyphon filled with R134a are not easily found in literature. Hence the

thermal behavior of R134a thermosyphon was undertaken in this work. This paper considers

the effect of controlling variables (Heat input, Coolant mass flow rate and coolant

temperature) on thermal performance of a flux controlled R134a thermosyphon.

WHY WE ARE COMPARING THE HEAT PIPE WITH THERMOSYPHON?

• General purpose of the heat pipe and thermosyphon to transfer the heat from one

position to the other.

• The heat pipe is very costly than compare with the thermosyphon.

• We have comparing the thermal conductivity of the thermosyphonwith the heat

pipe so that we provide the heat transfer equipment with the less cost.

• When compare with the thermosyphon the manufacturing method of the heat pipe

is more complex.

• We try to reduce the cost of manufacturing with the most efficient heat Transfer

with the high thermal conductivity.

2. EXPERIMENTAL DETAILS

2.1. Heat Pipe CAD Model designed using CATIA

Commonly referred to as a 3D Product Lifecycle Management software suite, CATIA

supports multiple stages of product development (CAX), including conceptualization, design

(CAD), engineering (CAE) and manufacturing (CAM). CATIA facilitates collaborative

engineering across disciplines around its 3DEXPERIENCE platform, including surfacing &

shape design, electrical, fluid and electronic systems design, mechanical engineering and

systems engineering.

CATIA facilitates the design of electronic, electrical, and distributed systems such as fluid

and HVAC systems, all the way to the production of documentation for manufacturing. The

Heat Pipe model is designed using CATIA, which is shown in the fig. 2.1.



Figure 2.1 Heat Pipe (3D shell) with thickness of 2mm

Thermosyphon CAD Model designed using CATIA

Figure 2.2 Thermosyphon (Wick less Heat Pipe)

Analysing the Thermosyphon Using ANSYS WorkBench

ANSYS have the wide range of applications in the finite element problems.

• It is used to find out the design considerations i.e. what the type of meshing we

need to provide the accurate results

• In the ANSYS part the boundary considerations requirements are compulsory

i.e. which face is needed to be fixed and what amount of force we need to

apply at what particular point

• In the ANSYS we find out the stresses development what amount of

deformations taking place without manufacturing the equipment to save the

expenditure over it.

Thermosyphon model which has developed in the CATIA has been imported to the

ANSYS workbench, and the mesh has been applied, which is shown in the figure 2.3.



Figure 2.3 Thermosyphon Mesh Model

The heat pipe cad model developed in CATIA has been imported in the same way as

Thermosyphon and mesh has been applied using ANSYS for applying the input parameters,

which is shown in the figure 2.4.

Figure 2.4 Heat Pipe Mesh Model

At diferent temperatures, the reperesentation of the thermosyphon is shown in the figure

2.5.



Figure 2.5 Different Temperatures of Thermosyphon

The trajectory of the input parameters applied to the thermosyphon mesh model for the

number of iterations is shown in the figure 2.6.

Figure 2.6 Input Parameters vs Iterations

In the same way, the analysis is carried out on the heat pipe, and for the different

temperatures of the heat pipe, it is shown in the figure 2.7, and the graphical representation of

the position of the heat pipe for different temperatures has been shown in the figure 2.8.



Figure 2.7 Different Temperatures of Heat Pipe

Figure 2.8 Different Temperatures vs Position

Manufacturing of Thermosyphon( Wick less Heat Pipe)

Initially, material for the thermosyphon is selected as copper(preferably), and the copper pipe

is made with two side opening. One of the side is closed with cap of parent material type by

welding and the pipe is filled with level of 30% and not more than 50% to provide an area for

the condensation. The other end of the pipe can be closed by thumb and pipe is heated to

change the phase of water to vapor. Side closed with thumb will be opened for small period to



form vacuum of certain level and then that side will be closed with cap to elevate vapor which

leads to a perfect wick less heat pipe. The thermosyphon which is manufactured by using the

procedure elucidated above is shown in the figure 2.9.

Figure 2.9 Thermosyphon (Wick less Heat Pipe)

Practical Evaluation of the Heat Pipe (Wick)

Figure 2.10 Heat Pipe Experimental Setup

The specifications of the heat pipe are given by

Length of the Heat Pipe = 300 mm

Diameter of the Heat Pipe = 30 mm

Area of the Heat Pipe = 176.25 mm2

Evaporator Length = 150 mm

Condenser Length = 150 mm

Effective Length of Heat Pipe = 125 mm

Wick Material = Copper

T1 = Avg. Evaporator Temperature

T2 = Avg. Condenser Temperature

The experiment is conducted for the different values of the T1 and T2 as shown in the

table 2.

Table 2 Average Condenser and Evaporator Temperatures

T1 30 36 40 43 50 57 62 65 70 75

T2 29 32 33 34 35 43 46 49 55 62



Practical Evaluation of Wick less Heat Pipe

Figure 2.11 Heat Pipe Experimental Setup

The temperature of the thermosyphon and the water at regular intervals of two minutes is

shown in the table 3.

Table 3 Temperature Variation of Thermosyphon

Sl. No. Thermosyphon

Temperature(0C)

Water

Temperature(0C)

Time

(min)

1 34 38 0

2 35 38 2

3 36 44 4

4 38 46 6

5 43 49 8

6 44 51 10

7 44 53 12

8 46 55 14

9 48 57 16

10 48 59 18

11 49 61 20

12 51 63 22

13 52 65 24

14 52 66 26

15 52 68 28

16 52 69 30

17 52 70 32

3. RESULTS AND DISCUSSION

3.1. Comparision of Temperature drop of Thermosyphon and Heat Pipe Using

ANSYS

After importing the Thermosyphon CAD Model and Heat Pipe CAD Model which are

designed in CATIA are analyzed using ANSYS Workbench and the positions of the

thermosyphon and the heat pipe with respect to total temperature mixture are shown in the

figure 3.1 and 3.2.



Figure 3.1 Thermosyphon Position for Total Temperature

Figure 3.2 Heat Pipe Position for Total Temperature

3.2. Evaluation of Effective Thermal Conductivity

The analysis of the thermosyphon and heat pipe carried out in the ANSYS Workbench gives

the position i.e. effective length, which is used to evaluate the effective thermal conductivity

of the thermosyphon and heat pipe as follows.

From the Fourier Law of Heat Conduction,

Q = K. A.

Where

Q = Heat input K = Effective thermal conductivity

dt = Temperature distribution dx = Effective length

A = Area through which heat flows

dt = (average evaporator temperature-average condenser temperature)

Heat Pipe:

Average evaporator temperature=1680K

Average condenser temperature=600K

Q=52.8 KW

A=114.5 mm2

52.8= Keff * 0.000706 * (11.6/0.125)

Keff= 1100 W/m0K



Thermosyphon:

X=23728

35.95= Keff*176.25 * 4.091 * (6/145)

Keff = 4930.72 W/m0K

3.3. Graphical Representation of Temperatures of Thermosyphon and Heat Pipe

w. r. t. Time

The graph has been plotted against temperature and time where series 1 represents

temperature variation of the heat pipe and series 2 represents the temperature variation of the

thermosyphon in the graph 1.

Graph 1 Temperature (0 C) vs Time (Minutes)

4. CONCLUSION

It has been revealed conducting series of experiments, that thermosyphon is having higher

effective thermal conductivity value compared to heat pipe which leads to maximum heat

transfer from one point to other. It has been observed that thermosyphon is reaching steady

state in less time when compared to heat pipe. The temperature drop is also less in

thermosyphon compared to heat pipe.

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