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Multiphase Simulation of TEAC Module

Yogesh Dalal

Hemanth Vadlamudi

Johnny James

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Abstract

Thermoelectrics has a growing interest in this era because of its satisfactory outcomes, yet to be

sophisticated, to become useful in large scale. This is what paves it to the need of optimization.

In this report, one such application of Thermoelectrics, i.e., Thermoelectric Air-Conditioning

(TEAC) is being discussed, which has come to the limelight in the area of automotive. As many

researches were done and still undergoing in this, TEAC performance is elevating the interest in

its optimization. So, in the present work, a prototype TEAC is modeled and is simulated under

air-to-air condition for results with the linkage of two different modules or phases in ANSYS.

The required outcomes are obtained and are compared with the analytical results.

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Contents

Page#

Absrtact……………………………………………………………………………….(i)

1. Introduction………..................................................................................................1

2. Literature review…………………………………………………………………...2

3. Theory……………………………………………………………………………...3

3.1 Thermoelectric cooler (TEC)…………………………………………………..3

3.2 Advantages of thermoelectric coolers………………………………………….4

3.3 Applications of TEC…………………………………………………………...5

3.4 Typical applications of TEC…………………………………………………...5

3.5 HVAC/TEAC………………………………………………………………….6

4. Project procedure…………………………………………………………………..8

4.1 Material selection………………………………………………………………8

4.2 Procedure………………………………………………………………………9

4.2.1 Material………………………………………………………………………9

4.2.2 Geometry……………………………………………………………………10

4.2.3 TEC module analysis………………………………………………………..13

4.2.4 Heat sink analysis (FLUENT)………………………………………………16

5. Observations………………………………………………………………………21

6. Conclusion………………………………………………………………………...26

7. References………………………………………………………………………...27

Appendix A

Appendix B

Appendix C

Appendix D (I)

Appendix D (II)

Appendix E (I)

Appendix E (II)

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List of figures

Page#

Fig-1: Electron concentration in a thermoelectric material……………………………………………3

Fig-2: An electrical circuit for thermoelectric cooling………………………………………...............4

Fig-3: Basic evaporation cycle………………………………………………………………...............7

Fig-4: Schematic of a prototype air-to-air TEAC system……………………………………………..7

Fig-5: Illustration showing the Multiphase approach…………………………………………………8

Fig-6: Isometric view of the modeled prototype……………………………………………………..12

Fig-7: 2D view of the modeled prototype……………………………………………………………13

Fig-8: Illustration showing the meshed elements of the modeled prototype………………...............13

Fig-9 (a): Illustration showing the temperature profile when 3.7 A is passed……………………….14

Fig-9 (b): Illustration showing the temperature profile when 3.7 A is passed……………………….15

Fig-10: Illustration showing the total heat flux when 3.7 A is passed……………………………….15

Fig-11: Illustration showing the total current density when 3.7 A is passed………………...............15

Fig-12: Illustration showing the meshed hot side duct and embedded hot heat sink………..............16

Fig-13: Illustration showing the temperature contours in the hot side duct at a velocity inlet of 0.0001m/s

and hot fin base temperature of 323K………………………………..................................................17

Fig-14: Illustration showing the velocity vectors in the hot side duct at a velocity inlet of 0.0001m/s and

hot fin base temperature of 323K…………………………………………………………………….17

Fig-15: Illustration showing the meshed cold side duct and embedded cold heat sink……………...18

Fig-16: Illustration showing the temperature contours in the cold side duct at a velocity inlet of 0.1m/s

and hot fin base temperature of 250K……………………………………………………………….19

Fig-17: Illustration showing the temperature contours in the hot side duct at a velocity inlet of 0.1m/s and

hot fin base temperature of 250K……………………………………………………………………20

Fig-18: Graphical representation of hot fin tip temperatures both analytically & from ANSYS…...23

Fig-19: Velocity vs fin tip temperature for cold heat sink at a given current (I) input……………...25

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List of tables

Page#

Table-1: Maximum inputs and outputs for Marlow RC12-4-01LS TEC Module…………….8

Table-2: Values of 𝑄ℎ and 𝑄𝑐 with obtained 𝑇𝑐 from ANSYS……………………………….21

Table-3: Comparison of power input from ANSYS results with ideal equations…………….22

Table-4: Comparison of 𝑇ℎ𝑡𝑖𝑝 from Ansys with analytical solution…………………………..23

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The conventional AC system installed in most of the automobiles around the world provides cool

air with the help of a refrigerant called R-134a. It replaced the previous gas in use, Freon; as it

was quite harmful to the environment. Even though the R-134a has a 1300 times greater

greenhouse gas effect than carbon-dioxide, it has still been in use since 1995. More than 90% of

the cars in USA have an air conditioning system installed in them. According to recent studies, it

is seen that car air conditioners leak around 10-70 gallons/year. Also a report submitted by

NREL suggested that 7-8 billion gallons of fuel is consumed per year for automotive A/C. Also

4-5 KW of power is required for centralized automotive A/C systems. In order to reduce the fuel

consumption and also to reduce the greenhouse effect, it has become necessary to search for an

alternative to replace the conventional A/C system [1]. The use of Thermoelectrics seems to

provide a promising alternative to this urgent need.

Thermoelectrics is actually connected with thermal and electrical phenomena. Thermoelectrics

can straightforwardly change thermal energy into electrical energy or the other way around. A

thermocouple utilizes the electrical potential (electromotive power) produced between two

different wires to measure temperature. Fundamentally, Thermoelectrics comprises of two

gadgets: a thermoelectric generator and a thermoelectric cooler. These gadgets have no moving

parts and are maintenance free. Thermoelectric generators have a great potential for waste heat

recovery from power plants and automobiles. This gadget likewise gives dependable power in

remote territories, for example, in space and at peak telecom destinations. Thermoelectric coolers

give refrigeration and temperature control in electronic bundles and therapeutic instruments.

Thermoelectrics has turned out to be progressively critical with various applications. Since

thermoelectricity was found in the mid nineteen century, there has not been much change in

proficiency and material until the late advancement of nanotechnology, which has prompted

exceptional change in execution [2].

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Dr.Lee, Alaa Attar & Sean Weera[8]; in their work discussed the experimental

validation of the optimum design for automotive air-to-air TEAC. They obtained the

TEAC optimum design by using a new optimal design method with dimensional analysis

that was recently developed. In order to simplify the problem, a unit cell that represented

the entire TEAC system was analytically calculated and was experimentally tested. Also

commercial TEC modules and heat sinks were selected and tested based on the analytical

optimum design results.

This work was the main basis for the present project. As the analysis of TEAC was

experimentally done, in the present project ANSYS is used as a tool to simulate similar

prototype to see if the required results are in good agreement with the analytical values.

Raut & Walke[9]; in their project tried to design a cooling system which was installed

on a conventional blower of a car AC. The purpose of their project was to make use of

the cold side of the TEC to cool the ambient air to a lower temperature, so that it can be

used as a personal cooler. They performed tests and took measurements for a commercial

automobile. They also incorporated a simple temperature controller to interface with the

cooling system. According to their results they were able to show that the TE cooling for

a car could be lowered by 7 degree Celsius than the ambient temperature.

Dr.HoSung Lee, text book on “Thermal Design”[2]; has provided the basic ideal

equations for solving the Thermoelectrics problems in the present project. Also, the

evaluation of heat sink efficiencies has become quite easy with enough knowledge

exhibited in this book.

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3.1 Thermoelectric Cooler (TEC)

In 1821, Thomas J. Seebeck found that an electromotive force or a potential difference could be

produced by a circuit using two different wires when one of the intersections was heated. This is

known as the Seebeck effect.

In 1834, Jean Peltier found the opposite process that the passage of an electric current through a

thermocouple produces heating or cooling depending on its direction. This is known as the

Peltier effect. In spite of the fact that the above two effects were exhibited to exist, it was

extremely hard to measure every effect as a property of the material on the grounds that the

Seebeck impact is constantly connected with two unique wires and the Peltier impact is

constantly trailed by the extra Joule heating that is heat generation because of the electrical

resistance of the passage of a current.

In 1854, William Thomson (later Lord Kelvin) found that if a temperature difference exists

between any two points of a current carrying conductor, heat is either freed or retained

depending on the direction of current and material, which is an addition to Peltier heating. This is

known as the Thomson impact.

When a temperature difference across a conductor is applied, the hot region of the conductor

produces free electrons and diffusion of the electrons occurs from the hot region to the cold

region. An electromotive force (EMF) is generated in a way that an electric current flows against

the temperature gradient [2].

Fig-1: Electron concentration in a thermoelectric material [2]

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Thermoelectric cooling uses the Peltier effect to create a heat flux between the junctions of

two different types of materials. A simple electrical circuit for thermoelectric cooling (TEC)

is shown in Figure below. The amount of heat absorbed at the cold junction is associated

with the Peltier cooling, the half of Joule heating, and the thermal conduction [2].

Fig-2: An electrical circuit for thermoelectric cooling [2]

3.2 Advantages of thermoelectric coolers:

No moving parts

Small and lightweight

Maintenance-free

Acoustically silent and electrically quiet

Heat or cool by changing direction of current flow

Wide operating temperature range

Highly precise temperature control (to within 0.1°C)

Operation in any orientation, zero gravity and high G- levels

Environmentally friendly

Sub-ambient cooling

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Has a long life, with mean time between failures (MTBF) exceeding 100,000

hours [3]

3.3 Applications of TEC

Applications for thermoelectric modules cover a wide range of product areas. These incorporate

hardware utilized by military, medical, industrial, consumer, exploratory/lab, and

telecommunication associations. Utilizations range from straightforward nourishment and drink

coolers for an evening excursion to a great degree modern temperature control frameworks in

rockets and space vehicles.

Dissimilar to a straightforward heat sink, a thermoelectric cooler permits bringing down the

temperature of an object beneath surrounding and in addition stabilizing the temperature of

objects which are subject to broadly fluctuating ambient conditions. A thermoelectric cooler is a

dynamic cooling module while a heat sink gives just passive cooling.

Thermoelectric coolers for the most part may be considered for applications that oblige heat

expulsion going from milliwatts up to a few thousand watts. Most single-stage TE coolers,

including both high and low current modules, are equipped for pumping a maximum of 3 to 6

watts for every square centimeter of module surface area. Different modules mounted thermally

in parallel may be utilized to build total heat pump execution. Huge thermoelectric frameworks

in the kilowatt extent have been built in the past for specific applications, for example, cooling

inside of submarines and railroad cars [4].

3.4 Typical applications of TEC:

Avionics

Black Box Cooling

Calorimeters

CCD (Charged Couple Devices)

CID (Charge Induced Devices)

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Cold Chambers

Cold Plates

Compact Heat Exchangers

Constant Temperature Baths

Dehumidifiers

Electronics Package Cooling

Heat Density Measurement

Immersion Coolers

Integrated Circuit Cooling

Infrared Calibration Sources and Black Body References

Infrared Detectors

Infrared Seeking Missiles

Laser Collimators

Laser Diode Coolers

Microprocessor Cooling

Night Vision Equipment

Power Generators (small)

Precision Device Cooling (Lasers and Microprocessors)

Refrigerators and on-board refrigeration systems (Aircraft, Automobile, Boat,

Hotel, Insulin, Portable/Picnic, Pharmaceutical, RV) [4]

3.5 HVAC/ TEAC

The conventional A/C in our automobile consists of a compressor, condenser, expansion valve

and evaporator. A container of compressed air gets exceptionally chilly in a short period of time

because of the fast expansion of the compressed gas. An automobile's A/C system works in the

same way. The refrigerant (R-134a) is packed in the compressor and transforms into a hot gas.

This hot gas is then cooled in the condenser to a fluid state and goes to the expansion valve. As

the refrigerant goes through the extension valve it comes back to a low-pressure gas and quickly

cools in the evaporator. A fan blows over the evaporator and cools the air that blows out the

vents [5].

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Fig-3 (a): Basic evaporation cycle [6]

Form the basic knowledge of HVAC, a thermoelectric cooling system is developed by

introducing a thermocouple module by replacing the convention air-conditioning system in an

automobile. There are two conditions under which the Thermoelectric Air-Conditioning (TEAC)

systems work; Air-to-Liquid and Air-to-Air system. In a recent work[8], air-to-air analysis has

shown best COP for the TEAC system when compared with an air-to-liquid system of the same

specifications. This is because of many reasons, like the high convective heat transfer coefficient

of liquid, leakages, friction etc. This is made as the base for this project to analyze the similar

situation with the help of ANSYS.

Fig-4: Schematic of a prototype air-to-air TEAC system[8]

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In this project, a multiphase approach is chosen for the analysis in ANSYS. For this

process, two modules of ANSYS are chosen which are executed simultaneously acquiring the

results from the preceding module. These two modules are; Thermal-Electric and Fluid Flow

(FLUENT). The process starts with material selection and then followed by the simulation of

TEC module and fins, respectively. Fig-5 shows the approach in brief.

Fig-5: Illustration showing the Multiphase approach

4.1 Material Selection

Initially, the thermoelectric module to be used is chosen as Marlow RC12-4-01LS. The properties

for both the p-type and n-type materials of the thermocouples are taken form the manufacturer’s

specifications at a maximum temperature of 500C. The specifications of this thermoelectric

module consisting of 127 thermocouples are given in Table-1.

Table-1: Maximum inputs and outputs for Marlow RC12-4-01LS TEC Module

Hot Side

Temperature

270C 500C

∆Tmax (0C-dry N2) 66 74

Qmax (watts) 36 39

Imax (amps) 3.7 3.7

Vmax (vdc) 14.7 16.4

AC resistance (ohms) 3.2 -

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It is to be decided from this stance, whether to start with the FLUENT module or the Thermal-

Electric module. In this project, Thermal-Electric module is considered first to simulate. This is

because; the TEC module can be simulated to get the cold junction temperature which can be

utilized as the base temperature while simulating the cold heat sink in FLUENT module.

4.2 Procedure:

4.2.1 Material

The materials of both p-type and n-type are given as inputs in the Engineering Data of

the Thermal-Electric module.

In the Engineering Data tab, the materials which are required to assign the elements that

are modeled are chosen from the material library (Engineering Data Sources). In this

project, the materials chosen are; Air, Ceramic, Copper Alloy, n-type and p-type

materials. The properties of each material chosen are briefed as below:

o Air

Isotropic Thermal Conductivity : 0.0257 W/mK

o Cermaic

Isotropic Thermal Conductivity : 180 W/mK

o Copper Alloy

Isotropic Thermal Conductivity : 401 W/mK

Isotropic Resistivity :

Temperature (0C) Resistivity (Ω-m)

0 1.548 x 10-8

20 1.694 x 10-8

100 2.277 x 10-8

o n-type

Isotropic Thermal Conductivity : 1.523 W/mK

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Isotropic Resistivity : 1.2028 x 10-5 Ω-m

Isotropic Seebeck Coefficient : -208.97 µV/K

o p-type

Isotropic Thermal Conductivity : 1.523 W/mK

Isotropic Resistivity : 1.2028 x 10-5 Ω-m

Isotropic Seebeck Coefficient : 208.97 µV/K

The p-type and n-type material properties of the thermocouple are obtained from half of the

effective material properties which are calculated from the manufacturer’s maximum values as

mentioned in the Table-1. In this project, the properties at 500C hot junction temperature are

considered calculations. These calculations can be referred from Appendix-A.

4.2.2 Geometry

Under the Thermal-Electric module, the whole TEAC prototype is modeled in the Geometry

tab. In this project, initially it was assumed to model a 12 couple TEC with the manufacturer’s

dimensions. Also, the ambient temperatures on both cold and hot sides are assumed and the base

temperatures are obtained from maximum input parameters to the single thermocouple analysis

for finding the optimum fin design. This proved out to be unfeasible as the optimum fin spacing

is beyond the base dimensions of the heat sink and also the fins thickness for both the heat sinks

are found to have negative magnitude. It is because the device which is modeled is of few

millimeters and more over the fin base assumed is sufficient to either dissipate or absorb the heat

on both the sides, respectively. It is concluded from the observations made after various trials

that the conventional formulae used to solve for the optimum fin design would give satisfactory

results if calculated for the whole device with 127 thermocouples.

After undergoing through series of discussions on the various assumed designs of heat sinks, a

final design was chosen whose efficiency is found out to be reasonable (Refer Appendix-B). The

modeling of the whole set up in brief is as follows:

In the Geometry window, XY-plane is chosen the base reference plane for the whole

geometry. The sketch of the 4 thermocouple module is drawn and then extruded with the

below dimensions from the manufacturer:

o p-base/ n-base

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Length : 3 mm/ 3 mm

Width : 1 mm/ 1 mm

Height : 1 mm/ 1 mm

o p-leg/ n-leg

Leg length : 1 mm/ 1 mm

Leg width : 1 mm/ 1 mm

Leg thickness : 1 mm/ 1 mm

o Top

Length : 3 mm

Width : 1 mm

Height : 1 mm

Now, ceramic layers are built on either sides on the base and the top of each

thermocouple which acts as insulators in the TEC analysis. About nine ceramic elements

are modeled of dimensions (3 mm x 1 mm x 1 mm) each.

Then, the fins are constructed on these ceramic layers. Below are the specifications of the

heat sinks:

o Cold heat sink:

Number of fins : 10

Fin profile length : 9 mm

Fin base width : 1 mm

In thickness : 1 mm

Heat sink base dimensions : 3 mm x 1 mm x 1 mm

It is to be noted that there are five pairs of cold heat sink fins which are constructed on five

ceramic bases beneath the p-type and n-type bases of the thermocouples.

o Hot heat sink:

Number of fins : 8

Fin profile length : 11 mm

Fin base width : 1 mm

In thickness : 1 mm

Heat sink base dimensions : 3 mm x 1 mm x 1 mm

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It is to be noted that there are four pairs of hot heat sink fins which are constructed on four

ceramic bases above the top surfaces of the thermocouples.

Finally, the air ducts are modeled on both the sides of the heat sinks. The dimensions of

the ducts on both the sides are as below:

o Cold side

Inlet/Outlet : 21 mm x 10 mm

Length of the duct : 20 mm

Distance between inlet/outlet and fin surface : 9 mm/10 mm

o Hot side

Inlet/Outlet : 19 mm x 12 mm

Length of the duct : 25 mm

Distance between inlet/outlet and fin surface : 14 mm/10 mm

Using the Boolean Operations the fins are separated from the ducts and restored to have

individual boundaries.

The inlets and outlets can be defined in this window using the Named Selection option.

Also the rest of the boundary conditions are defined.

The modeled prototype is shown in the Fig-6 and Fig-7.

Fig-6: Isometric view of the modeled prototype

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Fig-7: 2D view of the modeled prototype

4.2.3 TEC Module Analysis

Model

In the Thermal-Electric tab, Model is selected to mesh and simulate the modeled TEC

module. Here the materials are assigned to all the elements. These materials are initially

defined in the Engineering Data.

The duct boxes are suppressed in this stage as they don’t play a role in the TEC analysis.

The fins on both the sides can be left unsuppressed as they don’t participate in the

simulation because they are placed on the ceramic layers which act as insulators of

electricity.

Mesh

Finally, the model is coarse meshed as shown in the Fig-8.

Fig-8: Illustration showing the meshed elements of the modeled prototype

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Inputs

Now, the inputs are given to the TEC module. These are given below:

o Temperature: 500C is assigned at the top surfaces of all the thermocouples

which are treated as the hot junctions. This temperature is kept constant at these

junctions throughout the analysis.

o Voltage: 0 V is assigned at the face of n-type base of the array of thermocouples.

o Current: Here, a range of current is assumed to access different results each time.

Currents of 0.5 A, 1 A, 1.5 A, 2 A, 2.5 A, 3 A and 3.7 A are taken for analysis to

get seven set of results which can be used for further calculations. The current is

assigned in the opposite direction of the voltage, i.e., at the surface of the p-type

base of the thermocouple array.

o Convection: The rest of the faces which are left unassigned with any input,

except the base surfaces of the TEC couples, are assigned as convective surfaces

with a convective coefficient as 1 x 10-6 W/m2 .0C.

The only variable which is changed for the analysis of each case is the current.

Solution

In the solution menu, the required outputs are defined like the Total Heat Flux, Total

Current Density, Temperature profile, Temperature Probes at the required positions.

The solver is then run to get the results. The Fig-9 (a), Fig-9 (b), Fig-10 and Fig-11 shows

the temperature profile, total heat flux and total current density of the TEC module at a

given maximum current of 3.7 A.

Fig-9 (a): Illustration showing the temperature profile when 3.7 A is passed

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Fig-9 (b): Illustration showing the temperature profile when 3.7 A is passed

Fig-10: Illustration showing the total heat flux when 3.7 A is passed

Fig-11: Illustration showing the total current density when 3.7 A is passed

The ANSYS report for the above case is mentioned in Appendix-C.

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4.2.4 Heat Sink Analysis (FLUENT)

(a) Hot Side

Geometry

The geometry is imported from the Thermal-Electric module as discussed in the beginning. At

this stage there is no chance of editing the geometry. Now the elements of this prototype are

suppressed which do not come under the hot fin analysis. Only the hot heat sink and the hot side

duct are left for further analysis.

Mesh

A fine meshing is performed on the left over elements of the prototype or system which looks

like in the Fig-12 with the hot heat sink hidden inside the hot duct.

Fig-12: Illustration showing the meshed hot side duct and embedded hot heat sink

Solution

A pressure-based steady state analysis is chosen for solving.

The materials for both the hot fin system and the duct are assigned as Aluminum and air

(incompressible-ideal gas).

The required boundary conditions are assigned. At inlet a temperature of 300 K and a

series of velocities, .i.e., 0.0001 m/s, 0.001 m/s, 0.01 m/s, 0.1 m/s and 1 m/s are applied

for obtaining the outlet conditions of air at each instance. The inlet type is velocity-type

and the outlet is pressure-outlet type.

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The fin base temperature is set as 323 K (500C), which is same for all the cases. Also, the

duct wall temperatures are set to 300 K.

The solver is set to compute from the duct inlet with reference zone as the hot fins.

The solution scheme followed is Coupled. The solver is then initialized and run, solving

out for 100 iterations till the solution is converged.

The required results are visualized from Graphics and Animations by selecting the

appropriate boundary conditions which exhibit those results. For example, the variation

of the hot heat sink and duct outlet temperatures for an air inlet velocity of 0.0001 m/s is

shown in Fig-13. The velocity vectors are illustrated in the Fig-14.

Fig-13: Illustration showing the temperature contours in the hot side duct at a velocity

inlet of 0.0001m/s and hot fin base temperature of 323K

Fig-14: Illustration showing the velocity vectors in the hot side duct at a velocity inlet of

0.0001m/s and hot fin base temperature of 323K

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The illustrations for the rest of velocity inputs are provided in the Appendix-E (I). The ANSYS

report for the above case is exhibited in Appendix-D (I).

(b) Cold Side

Geometry

The geometry is imported from the Thermal-Electric module as discussed in the beginning. At

this stage there is no chance of editing the geometry. Now the elements of this prototype are

suppressed which do not come under the cold fin analysis. Only the cold heat sink and the cold

side duct are left for further analysis.

Mesh

A coarse mesh in this case is performed on the left over elements of the prototype or system,

unlike in the hot fin analysis, which looks like in the Fig-15 with the cold heat sink hidden inside

the cold duct.

Fig-15: Illustration showing the meshed cold side duct and embedded cold heat sink

Solution

A pressure-based steady state analysis is chosen for solving as in the case of hot fin

analysis.

The materials for both the cold fin system and the duct are assigned as Aluminum and air

(incompressible-ideal gas).

The required boundary conditions are assigned. At inlet a temperature of 295 K and a

series of velocities, .i.e., 0.0001 m/s, 0.001 m/s, 0.01 m/s, 0.1 m/s and 1 m/s are applied

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for obtaining the outlet conditions of air at each instance. The inlet type is velocity-type

and the outlet is pressure-outlet type.

The fin base temperature is taken as 250 K, 254 K, 259 K, 265 K, 275 K, 287 K and 303

K, which are the cold junction temperatures obtained for the different current inputs as

specified in the beginning, i.e., 3.7 A, 3 A, 2.5 A, 2 A, 1.5 A, 1 A and 0.5 A,

respectively. Also, the duct wall temperatures are set to 295 K.

The solver is set to compute from the duct inlet with reference zone as the cold fins.

The solution scheme followed is Coupled. The solver is then initialized and run, solving

out for 100 iterations till the solution is converged.

The required results are visualized from Graphics and Animations by selecting the appropriate

boundary conditions which exhibit those results. For example, the variation of the cold heat sink

and duct outlet temperatures for an air inlet velocity of 0.1 m/s and cold fin base temperature of

250 K is shown in Fig-16. The velocity vectors are illustrated in the Fig-17.

Fig-16: Illustration showing the temperature contours in the cold side duct at a velocity

inlet of 0.1m/s and hot fin base temperature of 250K

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Fig-17: Illustration showing the temperature contours in the hot side duct at a velocity inlet

of 0.1m/s and hot fin base temperature of 250K

The illustrations for the rest of velocity inputs are provided in the Appendix-E (II). The ANSYS

report for the above case is also exhibited in Appendix-D (II).

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Form the ANSYS analysis, it is noticed that few aspects play a vital role in getting the expected

results. Though the results which are computationally obtained may not be the same in real time

situations, but as per the given boundary conditions and the inputs, the results obtained are quite

satisfactory.

On doing the TEC analysis in ANSYS, the cold junction temperatures (Tc) for different current

inputs are obtained keeping hot junction temperature (Th) as constant at 323 K. Using these Tc

values, cooling power (Qc), heat dissipated (Qh) and the power input (Win) are calculated from

the ideal equations. The effective material properties are used in solving the ideal equations

(Appendix-A). The results are summarized in Table-2.

Table-2: Values of Qh and Qc with obtained Tc from ANSYS

Current (I), amp Voltage (V), volt Tc (K) Qh, watts Qc, watts

0.5 0.08145 303.183 0.49 0.446

1 0.15593 287.54 0.966 0.794

1.5 0.22477 275.283 1.434 1.061

2 0.28889 265.867 1.9 1.259

2.5 0.34851 259.159 2.367 1.397

3 0.40540 254.088 2.843 1.486

3.7 (max) 0.47961 250.266 3.326 1.536

From the above results, the power input is evaluated and is compared with the resultant power

input from ANSYS simulation. The results are summarized in Table-3.

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Table-3: Comparison of power input from ANSYS results with ideal equations

Current (I), amp Win (Ideal equation) Win (Ansys)

0.5 0.045 0.0406

1 0.172 0.1561

1.5 0.373 0.3387

2 0.641 0.5764

2.5 0.97 0.8730

3 1.359 1.2138

3.7 (max) 1.991 1.7715

From Table-3, it can be drawn that the results are in good agreement. The error between the two

sets of values may be because of the assumed convective surfaces in TEC analysis in ANSYS.

So, due to the low convective heat transfer coefficient given to the TEC thermocouple surfaces,

the heat dissipated and absorbed along these surfaces might sufficiently be reducing the Win.

The main intention to perform an ANSYS simulation is to find out the outlet air conditions in

both hot side and cold side ducts. So air is given different velocities at the inlet on both the sides

and considerable observations are made. Table-4 and Fig-18 shows the variation of outlet air

temperature and also the ambient temperature of air at the fin tip (Thtip) in the hot side heat sink.

28 | P a g e

Table-4: Comparison of Thtip from Ansys with analytical solution

Velocity (m/s)

Inlet temperature

(Tin), K

Outlet temperature

(Tout), K

Fin tip temperature (Thtip), K

Analytical

(Tin+ Tout)/2

ANSYS

0.0001 300 343 321.5 323.59

0.001 300 328 314 315

0.01 300 310 305 314

0.1 300 316 308 310

1 300 304.59 302.295 308.47

Fig-18: Graphical representation of hot fin tip temperatures both analytically & from

ANSYS

From the Fig it can be seen that the results are in good agreement with each other.

Similarly the fin tip temperatures at the cold side is also found out for the range of inlet air

velocities and at different current (I) inputs which are illustrated in the below Fig-19.

290

295

300

305

310

315

320

325

330

0.0001 0.001 0.01 0.1 1

Fin

tip

te

mp

era

ture

(K

)

Velocity (m/s)

Anatically

Ansys

29 | P a g e

(a) At 0.5 A (b) At 1 A

(c) At 1.5 A (d) At 2 A

(e) At 2.5 A (f) At 3 A

286

288

290

292

294

296

298

Fin

tip

te

mp

era

ture

(K

)

Velocity (m/s)

Anatically

Ansys 284286288290292294296298

Fin

tip

te

mp

era

ture

(K

)

Velocity (m/s)

Anatically

Ansys

280

285

290

295

300

Fin

tip

te

mp

era

ture

(K

)

Velocity (m/s)

Anatically

Ansys 282284286288290292294296298

0.0

00

1

0.0

01

0.0

1

0.1 1

Fin

tip

te

mp

era

ture

(K)

Velocity (m/s

Anatically

Ansys

284

286

288

290

292

294

296

Fin

tip

te

mp

era

ture

(K

)

Velocity (m/s)

Anatically

Ansys275

280

285

290

295

300

0.0

00

1

0.0

01

0.0

1

0.1 1

Fin

tip

te

mp

era

ture

(K

)

Velocity (m/s)

Anatically

Ansys

30 | P a g e

(g) At 3.7 A

Fig-19: Velocity vs fin tip temperature for cold heat sink at a given current (I) input

270

275

280

285

290

295

300

Fin

tip

te

mp

era

ture

(K)

Velocity (m/s)

Anatically

Ansys

31 | P a g e

Conclusion

It can be concluded that the assumed design for TEAC system is feasible. This Multiphase

approach can be used to compare with the real time TEAC modules both in academic and

commercial areas. The results from Multiphase approach may not be accurate for a decision to be

taken by them, but are still appreciable for a preliminary judgment whether the considered

module produces the near desired effect.

In future, this approach can be used to design a commercial TEAC module and analyze it

preliminarily before performing an experiment to check the boundary conditions and outcomes

that’s where it can be justified as a commercially acceptable approach.

32 | P a g e

References

[1]

http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2006/session6/2006_deer_fairb

anks.pdf

[2] H. Lee, Thermal Design: Heat Sinks, Thermoelectrics, Heat Pipes, Compact Heat

Exchangers, and Solar Cells, Hoboken: John Wiley & Sons, Inc., 2010.

[4] http://www.pathways.cu.edu.eg/ec/text-pdf/part%20c-17.pdf

[5] https://www.ferrotec.com/technology/thermoelectric/thermalRef03

[6] http://www.autoeducation.com/autoshop101/hvac.htm

[7] http://home.howstuffworks.com/ac2.htm

[8] Attar, Alaa and Lee, HoSung, “Experimental Validation of the Optimum Design of

Automotive Air-to-Air Air Conditioner (TEAC)”, Journal of Electronic Materials, Vol.44,

No.6, 2177-2185 (2015).

[9] M. S. Raut and D. V. Walke, "Thermoelectric Air Cooling For Cars", International

Journal of Engineering Science and Technology (IJEST), vol. 4, no. 5, pp. 2381-2394,

2012.