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1 Performance Prediction of Commercial Thermoelectric Cooler Modules using the Effective Material Properties HoSung Lee, Alaa M. Attar, Sean L. Weera Mechanical and Aerospace Engineering, Western Michigan University, 1903 W. Michigan Ave, Kalamazoo, Michigan 49008-5343, USA Office (269) 276-3429 Fax (269) 276-3421 Email: [email protected] Abstract This work examines the validity of formulating the effective thermoelectric material properties as a way to predict thermoelectric module performance. The three maximum parameters (temperature difference, current, and cooling power) of a thermoelectric cooler were formulated on the basis of the hot junction temperature. Then, the effective material properties (Seebeck coefficient, electrical resistance, and thermal conductivity) were defined in terms of the three maximum parameters that were taken from either a commercial thermoelectric cooler module or the measurements. It is demonstrated that the simple standard equation with the effective material properties predicts well the performance curves of the four selected commercial products. Normalized parameters over the maximum parameters were also formulated to present the characteristics of the

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Performance Prediction of Commercial Thermoelectric Cooler

Modules using the Effective Material Properties

HoSung Lee, Alaa M. Attar, Sean L. Weera

Mechanical and Aerospace Engineering, Western Michigan University,

1903 W. Michigan Ave, Kalamazoo, Michigan 49008-5343, USA

Office (269) 276-3429

Fax (269) 276-3421

Email: [email protected]

Abstract

This work examines the validity of formulating the effective thermoelectric material

properties as a way to predict thermoelectric module performance. The three maximum

parameters (temperature difference, current, and cooling power) of a thermoelectric

cooler were formulated on the basis of the hot junction temperature. Then, the effective

material properties (Seebeck coefficient, electrical resistance, and thermal conductivity)

were defined in terms of the three maximum parameters that were taken from either a

commercial thermoelectric cooler module or the measurements. It is demonstrated that

the simple standard equation with the effective material properties predicts well the

performance curves of the four selected commercial products. Normalized parameters

over the maximum parameters were also formulated to present the characteristics of the

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thermoelectric coolers along with the normalized charts. The normalized charts would be

universal for a given thermoelectric material.

Keywords: Thermoelectric cooler, thermoelectric module, effective material

properties, maximum parameters, normalized parameters, and normalized charts.

Nomenclature

A cross-sectional area of thermoelement (m2)

COP the coefficient of performance, dimensionless

I electric current (A)

maxI maximum current (A)

j

electric current density vector (A/m2)

K thermal conductance (W/K)

L length of thermoelement (m)

k thermal conductivity (W/mK)

n the number of thermocouples

q

heat flux vector (W/m2)

cQ cooling power, heat absorbed at cold junction (W)

hQ heat liberated at hot junction (W)

maxcQ maximum cooling power (W)

R electrical resistance ()

T temperature (°C)

cT low junction temperature (°C)

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hT high junction temperature (°C)

T average temperature 2ch TT (°C)

V Voltage of a module (V)

maxV maximum voltage (V)

W work per unit time RITIW 2 (W)

x distance of thermoelement leg (m)

Z the figure of merit (K-1), kZ 2

T temperature difference ch TT (°C),

maxT maximum temperature difference (°C)

Greek symbols

Seebeck coefficient (V/K)

electrical resistivity (cm)

gradient operator vector

Subscript

p p-type element

n n-type element

Superscript

* effective quantity

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1. Introduction

Thermoelectric coolers have comprehensive applications [1-5] in electronic devices,

medical instruments, automotive air conditioners, and refrigerators. Thermoelectric

phenomena are often described by a simple standard equation, which has been widely

used in the literature [1-5], sometimes in good agreement with experiment [6,9,11]. The

simple standard equation is herein called the ideal equation, which is virtually formulated

under three assumptions that the electrical and thermal contact resistances, the Thomson

effect (temperature-dependent Seebeck coefficient), and the radiation and convection heat

transfer are negligible [11,12]. The radiation and convection heat transfer is small for the

moderate temperature differences between the hot and cold junction temperatures and the

surrounding temperature in typical commercial cooler modules. The Thomson effect

rather slightly improves the performance [6,7]. The major errors between the

measurements and the ideal equation lie on the electrical and thermal contact resistances

[11,13].

Commercial thermoelectric cooler modules consist of a number of thermoelement

couples (or thermocouples), electrically connected in series and thermally sandwiched in

parallel between two ceramic plates. The manufacturers usually provide the performance

curves along with the maximum parameters such as the temperature difference Tmax, the

current Imax, the cooling power Qmax, and the voltage Vmax. However, the material

properties of the modules such as the Seebeck coefficient , the electrical resistivity ,

and the thermal conductivity k are not usually provided as manufacturers’ proprietary

information. Therefore, system designers find it difficult to obtain the material properties.

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Huang et al. [14] measured the material properties of a commercial module for the

optimum design using an evacuated and insulated test apparatus. They confirmed that the

measurements were in good agreement with the performance curves provided by the

manufacturer. Nevertheless, they were not able to fit the measured data to the ideal

equation, which was deemed mainly due to the electrical and thermal contact resistances

not counted for within the ideal equation.

Lineykin and Ben-Yaakov [15] formulated the theoretical maximum parameters

from the ideal equation using the definitions used by manufacturers and then expressed

the physical module properties (m, Rm, and Km) in terms of the three parameters (Tmax,

Imax, and Vmax) out of the four theoretical maximum parameters (Tmax, Imax, Qmax, and

Vmax). In this way, the module properties contain information of the number of

thermoelement couples and geometric ratio. Lineykin and Ben-Yaakov extracted the

physical module properties by substituting the manufacturers’ maximum parameters for

the theoretical maximum parameters. Luo [16] used two methods to determine the

physical module properties: not only the combination (Tmax, Imax, and Vmax) used by

Lineykin and Ben-Yaakov, but also the different combination (Tmax, Imax, and Qmax) out

of the four maximum parameters. When the two methods were compared to each other

over four selected commercial modules, the physical module properties over the four

modules varied within a 5% discrepancy range. Zhang [17] obtained the physical module

properties of a commercial module using the three parameters (Tmax, Imax, and Vmax) for

application to an electronic cooling system and performed evaluation and optimization

onto the system design, including the heat sinks.

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Simons [21] showed a capability of the module properties (m, Rm, and Km) with a

different set of the maximum parameters (Tmax, Imax, and Qmax) to predict the

performance of an electronic module. Tan and Fok [10] evaluated the module properties

for commercial modules using the three maximum parameters (Tmax, Imax, and Vmax) and

compared the predicted results with the manufacturers’ performance curves. The

comparisons showed fair agreement and the errors increased with increasing current or

temperature difference. Recently, Ahiska and Ahiska [18] developed a new economic

method of measurement for thermoelectric outputs and properties providing formulas

based on the ideal equation by measuring the maximum parameters (Tmax, Imax, and

Vmax) and experimentally proved to be reasonably accurate.

Most of the above mentioned works tried to extract the physical module properties

(m, Rm, and Km) from either the three parameters (Tmax, Imax, and Vmax) or the other set

of parameters (Tmax, Imax, and Qmax), which imposes the uncertainties on the cooling

power prediction. On the other hand, the present work extracts the effective material

properties (and k) from the manufacturers’ maximum parameters (Tmax, Imax, and

Qmax), which imposes the uncertainties on the voltage prediction, particularly being good

at module design for specific systems. Note that, although the differences between the

module properties and the effective material properties appear minuscule, the results and

applications are of great consequence: the module properties are constrained to have a

validity for use of the module, but the effective material properties are not, which is the

uniqueness of the present paper. The optimal design [8] using the ideal equation with the

effective material properties will now be simple and robust. The present work studies to

verify in detail the effective material properties comparing with the performance curves

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of four major manufacturers’ products. Hence, the usually intractable temperature

dependence of the material properties and the subtle thermal and electrical contact

resistances can be examined with the effective material properties that are constant.

The normalized charts with the maximum parameters were presented by Buist [19]

and later Uemura [20] for the purpose of the design of thermoelectric devices. However,

theoretical formulas for the normalized charts were not found to the authors’ knowledge.

Therefore, the present work studies the normalized formulas over the maximum

parameters providing the two normalized charts, which coherently reveal the elusive

general characteristics of thermoelectric coolers.

p

n

p

n

np

p

pn

Positive (+)

Negative (-)

Heat Absorbed

Heat Rejected

Electrical Conductor (copper)Electrical Insulator (Ceramic)

p-type Semiconcuctor

n-type Semiconductor

Figure 1. Cutaway of a typical thermoelectric module

1. Ideal Equation

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A typical thermoelectric module is shown in Figure 1. Suppose that the upper junction

temperature (upper electrical conductor) is at Tc and the lower junction temperature is at

Th. The cooling power at the junction of temperature Tc is given by

TKRIITnQ cc

2

2

1 (1)

where n is the number of thermocouples, a the Seebeck coefficient, I the current, R the

electrical resistance, K the thermal conductance, and T = (Th - Tc). From now on,

Equation (1) is called the ideal equation. The current for the optimum COP can be

obtained by differentiating COP and setting it to zero.

11

TZR

TICOP

(2)

where kZ 2 and T is the average temperature of cT and hT . On the basis of Th,

TZ is expressed by

h

hT

TZTTZ

21 (3)

2. Maximum Parameters

Let us consider a thermoelectric module shown in Figure 1 for the theoretical

maximum parameters with the ideal equation. The module consists of a number of

thermoelement couples as shown. As mentioned before, the ideal equation assumes that

there are no the electrical and thermal contact resistances, no Thomson effect, and no

radiation or convection. It is noted that the theoretical maximum parameters might differ

with the manufacturers’ maximum parameters that are usually obtained by measurement.

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The maximum current Imax is the current that produces the maximum possible

temperature difference Tmax , which always occurs when the cooling power is at zero.

This is obtained by setting cQ = 0 in Equation (1), replacing Tc with (Th – T) and taking

derivative of T with respect to I and setting it to zero. The maximum current is finally

expressed by

ZT

ZT

RI hh

11 2

2

max

(4)

Or, equivalently in terms of Tmax,

R

TTI h max

max

(5)

The maximum temperature difference Tmax always occurs when the cooling power

is at zero and the current is at maximum. This is obtained by setting cQ = 0 in Equation

(1), substituting both I and Tc by Imax and Th – Tmax, respectively, and solving for Tmax.

The maximum temperature difference is obtained as

2

2

max

11hhh T

ZT

ZTT

(6)

The maximum cooling power maxcQ is the maximum thermal load which occurs at

T = 0 and I = Imax. This can be obtained by substituting both I and Tc in Equation (1) by

Imax and Th (since Tc = Th ), respectively, and solving for maxcQ . The maximum cooling

power for a thermoelectric module with n thermoelement couples is

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R

TTnQ h

c2

2

max

22

max

(7)

The maximum voltage is the DC voltage which delivers the maximum possible

temperature difference Tmax when I = Imax. The maximum voltage is given by

hTnV max (8)

3. Normalized Parameters

If we divide the actual values by the maximum values, we can normalize the

characteristics of the thermoelectric cooler. The normalized cooling power can be

obtained by dividing Equation (1) by Equation (7), which is

RTTn

TKRIITTn

Q

Q

h

h

c

c

2

2

1

2

max

22

2

max

(9)

which, in terms of the normalized current and normalized temperature difference, reduces

to

2

max

max

max

max

2

max

max

max

max

max

max

max

1

2

1

1

1

12

h

h

h

h

h

h

h

c

c

T

TZT

T

T

T

T

T

T

I

I

T

T

T

T

I

I

T

T

T

T

Q

Q

(10)

where

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11

11

1

2

max

hhh ZTZTT

T (11)

The coefficient of performance in terms of the normalized values is

2

max

max

max

max

max

max

max

max

2

max

max

max

max

max

1

1

12

11

I

I

T

T

I

I

T

T

T

T

T

TZT

T

T

T

T

I

I

T

T

I

I

T

T

T

T

COP

hh

h

h

h

hh

(12)

The normalized voltage is

max

maxmax

maxmax

1I

I

T

T

T

T

T

T

V

V

hh

(13)

The normalized current for the optimum COP is obtained from Equation (2).

111 max

max

max

max

TZT

T

T

T

T

T

I

I

h

hCOP (14)

where TZ is expressed using Equation (3) by

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max

max

2

11

T

T

T

TZTTZ

h

h (15)

Note that the above normalized values in Equations (10), (11), (12) and (13) are functions

only of three parameters, which are maxTT , maxII and ZTh.

4. Effective Material Properties

The effective material properties are defined here as the material properties that are

extracted from the maximum parameters provided by the manufacturers or from

measurements. The effective figure of merit is obtained from Equation (6), which is

2max

max2

TT

TZ

h

(16)

The effective Seebeck coefficient is obtained using Equations (5) and (7), which is

maxmax

max2

TTnI

Q

h

c

(17)

The effective electrical resistivity can be obtained using Equation (5), which is

max

max

I

LATTh

(18)

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The effective thermal conductivity is now obtained, which is

Zk

2

(19)

The effective material properties include all the losses such as the contact resistances.

Hence, the effective figure of merit appears slightly less than the intrinsic figure of merit

as shown in Table 1. Since the material properties were obtained for a p-type and n-type

thermoelement couple, the material properties of a thermoelement should be obtained by

dividing by 2.

5. Results and Discussion

In the previous reports [15-17], the physical module properties (m, Rm, and Km)

were extracted from a combination (Tmax, Imax, and Vmax) among the four manufacturer’s

maximum parameters (Tmax, Imax, maxcQ , and Vmax). In the present work, the effective

material properties (, , and k*) were extracted from a different combination (Tmax,

Imax, and maxcQ ) among the manufacturers’ maximum parameters. Therefore, the physical

module properties hold information of the number of thermoelement couples and the

geometric ratio (A/L), while the effective material properties do not.

In order to examine the status of the ideal equation with the effective material

properties, several major manufacturers were chosen as shown in Table 1. The effective

material properties were first calculated using the manufacturer’s maximum parameters

using Equations (16) - (19). The geometry of A and L were actually measured. Only one

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set of the intrinsic material properties was provided by the manufacturer, which is shown

in Table 1.

In the column of Module CP10-127-05, the effective material properties obtained

appear very close to the intrinsic material properties. It should be noted that the

dimensionless intrinsic figure of merit of 0.803 exhibits slightly larger than the

dimensionless effective figure of merit of 0.744, which is reasonable because the contact

resistances are conceptually imposed on the effective material properties. No appreciable

improvement was found even though the intrinsic material properties were used in

calculation because the contact resistances exist anyway. It is noted that the maximum

temperature differences provided by different manufactures may not be consistent with

one another. The manufacturability and contact resistances may be responsible for the

inconsistency.

Table 1 Comparison of the properties and dimensions for the commercial products of

thermoelectric modules

Description TEC Module (Bismuth Telluride)

Symbols CP10-127-05

(Th=298 K)

RC12-4

(Th=298 K)

TB-127-1.0-1.3

(Th=298 K)

C2-30-1503

(Th=298 K)

# of thermocouples n 127 127 127 127

Intrinsic material

properties (provided

by manufacturers)

V/K 202.17 - - -

cm 1.01 x 10-3 - - -

k (W/cmK) 1.51 x 10-2 - - -

ZTh 0.803 - - -

Effective material

properties (calculated

using commercial

Tmax, Imax, and Qcmax)

V/K 189.2 211.1 204.5 208.5

cm 0.9 x 10-3 1.15 x 10-3 1.0 x 10-3 1.0 x 10-3

k (W/cmK) 1.6 x 10-2 1.7 x 10-2 1.6 x 10-2 1.7 x 10-2

ZTh 0.744 0.673 0.776 0.758

Measured geometry

of thermoelement

A (mm2) 1.0 1.0 1.0 1.21

L (mm) 1.25 1.17 1.3 1.66

G=A/L (cm) 0.080 0.085 0.077 0.073

Dimension (W×L×H) mm 30 × 30 × 3.2 30 × 30 ×

3.4

30 × 30 × 3.6 30 × 30 × 3.7

Manufacturers’

maximum parameters Tmax (°C) 67 66 (63) 69 68

Imax (A) 3.9 3.7 3.6 3.5

Qcmax (W) 34.3 36 34.5 34.1

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Vmax (V) 14.4 14.7 15.7 15.5

R () -

module

3.36 3.2 3.2 3.85

Figure 2 depicts comparison between the calculations (solid lines) and the

manufacturer’s performance data (triangles) of Module CP10-127-05. The cooling power

in Figure 2 (a) was calculated using Equation (7) by substituting Tc by (Th –T) and using

the effective material properties. The dotted curve indicates the cooling power at the

optimal COP for which Equation (7) was used with substituting I by the current at the

optimum COP in Equation (2). It is seen in Figure 2 (a) that the calculated effective

maximum parameters (Tmax = 67°C, Imax = 3.9 A, and maxcQ = 34.3 W) are in good

agreement with the manufacturer’s performance curves. On the other hand, Figure 2 (b)

depicts that the errors on the voltage-vs-temperature-difference curves increase with

decreasing the temperature difference. The errors are associated with the combination

(Tmax, Imax, and maxcQ ) and partially the inherent contact resistances. The analysis

including the temperature dependence of the material properties and the thermal and

electrical contact resistances are very formidable especially for optimal system design

which requires many iterations of calculations, also not available in the literature to the

authors’ knowledge. Therefore, the errors are a nature of this work. The present work

presents a single module, but system design involves multiple modules. However, the

multiple modules in a system may be effectively handled using a thermal isolation

technique [22]. The marked data of the COP in Figure 2 (c) were not provided by the

manufacturer but generated in this work using the measured data in Figures 2 (a) and (b),

which are in a fair agreement.

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0 10 20 30 40 50 60 700

5

10

15

20

25

30

35

Temperature Difference, T (°C)

Coo

ling

Pow

er, Q

c (

W)

I = 3.9 A Prediction

Commercial product

3.2 A Optimal COP

2.4 A

1.6 A

0.8 A

(a)

0 10 20 30 40 50 60 700

2

4

6

8

10

12

14

16

18

Temperature Difference (°C)

Volt

age (

V)

Prediction

Commercial productI = 3.9 A

3.2 A

2.4 A

1.6 A

0.8 A

(b)

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0 1 2 3 40

0.5

1

1.5

2

2.5

3

Current (A)

CO

PPrediction

Commercial product

T = 10°C

20 °C

30 °C

40 °C

50 °C

(c)

Figure 2. (a) Cooling power versus T, (b) Voltage versus T, as a function of current,

and (c) COP versus current as a function of T. The original performance data (triangles)

of the commercial module (Module CP10-127-05) are compared to the prediction (solid

lines). The dotted line in (a) indicates the cooling powers at the optimum COP.

Figures 3 (a) and (b) depict comparison between the calculations and the

performance data of Module RC12-4. In general, the calculations are in good agreement

with the manufacturer’s performance data. Figure 3 (c) shows only the calculations (solid

lines) wherein the COP data (dotted lines) were not able to be generated due to the lack

of information from the manufacturer.

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0 0.5 1 1.5 2 2.5 3 3.5 40

10

20

30

40

50

60

70

Prediction Qc = 0 W

Commercial product

Qc = 5 W

Qc = 10 W

Qc = 15 W

T (°C)

Qc = 20 W

Qc = 25 W

Qc = 30 W

Qc = 35 W

I (A)

(a)

0 1 2 3 4 50

5

10

15

20

25

30

Prediction, Qc = 0

Prediction, T = 0

Comm. product, Qc = 0

Comm. product, T = 0

Current (A)

Vo

ltag

e (

V)

Qc = 0

T 0

(b)

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0 1 2 3 40

0.5

1

1.5

2

2.5

3

Current (A)

CO

PPrediction

No commercial product

T = 13.2°C

26.4°C

39.6°C

52.8°C

Figure 3. (a) T versus current as a function of cooling powers, (b) Voltage versus

current for Qc = 0 and T = 0, respectively, and (c) COP versus current. The original

performance data (triangles and squares) in (a) and (b) of the commercial module

(Module RC12-4) are compared to the prediction (solid lines).

Figures 4 (a), (b) and (c) depict comparison between the calculations and the

performance data of Module TB-127-1.0-1.3, with an excellent agreement.

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0 10 20 30 40 50 60 700

5

10

15

20

25

30

35

Temperature Difference, T (°C)

Coo

ling

Pow

er, Q

c (

W)

Prediction I = 3.6 A

Commercial product

Optimal COP

2.7 A

1.8 A

0.9 A

(a)

0 1 2 3 40

2

4

6

8

10

12

14

16

Current (A)

Vo

ltag

e (

V)

T = 69°C

T = 51.75°C

T = 34.5°C

T = 17.25°C

Prediction

Commercial product

(b)

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0 1 2 3 40

0.4

0.8

1.2

1.6

2

Current (A)

CO

PPrediction

Commercial product

T = 17.25°C

34.5°C

51.75°C

(c)

Figure 4 (a) Cooling power versus T as a function of current, (b) Voltage versus current

as a function of T, and (c) COP versus current as a function of T. The original

performance data (triangles) of the commercial module (Module TB-127-1.0-1.3)

compared to the prediction (solid lines). The dotted line in (a) indicates the cooling

powers at the optimum COP.

Figures 5 (a), (b) and (c) depicts comparison between the calculations and the

performance data of Module C2-30-1503, with a good agreement.

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22

0 10 20 30 40 50 60 700

5

10

15

20

25

30

35

Temperature Difference, T (°C)

Coo

ling

Pow

er, Q

c (

W)

I = 3.5 APrediction

Commercial product3 A

Optimal COP

2.5 A

2 A

1.5 A

1 A

(a)

0 10 20 30 40 50 60 700

2

4

6

8

10

12

14

16

Temperature Difference (°C)

Volt

age (

V)

I = 3.5 A

3 A

2.5 A

2 A

1.5 A

1 A

Prediction

Commercial product

(b)

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23

0 1 2 3 40

0.5

1

1.5

2

2.5

3

Current (A)

CO

PT = 10°C Prediction

Commercial product

20°C

30°C

40°C

50°C

(c)

Figure 5. (a) Cooling power versus T as a function of current, (b) voltage versus T, as

a function of current, and (c) COP versus current as a function of T. The original

performance data (triangles) of the commercial module (Module C2-30-1503) are

compared to the prediction (solid lines). The dotted line in (a) indicates the cooling

powers at the optimum COP.

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

I/Imax = 1.0 I/Imax = 1.0

0.8 0.8

0.6 0.6

Qc/Qcmax 0.4 V/Vmax

0.4

0.2

0.2

T/Tmax Figure 6. Normalized chart I: cooling power and voltage versus T as a function of

current. The solid lines depict the data at ZTh = 0.75, while the dotted lines depict the

alternate current ratios at ZTh = 0.4. The dashed line depicts the cooling power ratios at

the optimum COP.

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0

0.5

1

1.5

2

2.5

3

T/Tmax = 0 T/Tmax = 0

0.2 0.2

0.4

Qc/Qcmax COP

0.6

0.4

0.8 0.6

0.8

I/Imax Figure 7. Normalized chart II: cooling power and COP versus current as a function of T.

The solid lines depict the data at ZTh = 0.7, while the dotted lines depict the alternate

temperature difference ratios at ZTh = 0.4.

Figures 6 and 7 depict the normalized cooling power maxcc QQ , COP, and voltage

maxVV , which were plotted using Equations (27), (29), and (30), respectively. The above

three dependent parameters are only functions of three independent parameters: I/Imax,

T/Tmax, and ZTh as shown in the equations. From the previous discussion, we learned

that the ideal equation with the effective material properties predicts well the real

performance of a thermoelectric cooler module. These normalized charts should also

predict well the performance with a given ZTh. The solid lines depict the predictions at

ZTh = 0.75, which is a typical dimensionless figure of merit used in the commercial

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products. In order to see the effect of ZTh, the predictions at ZTh = 0.4 were plotted as the

dotted lines for comparison. We find from the figures that the normalized charts are not

significantly influenced by ZTh. These charts are then considered being universal to

approximately represent the performance of most thermoelectric cooler modules in the

present market. With inserting the maximum parameters provided by the manufacturers

into the charts, the reasonable cooling power, COP and voltage could be obtained as

functions of current and temperature difference.

6. Conclusions

The accuracy of the ideal equation in connection with the effective material

properties is demonstrated by comparing with several manufacturers’ performance data

(which are usually obtained by the measurements), being in good agreement. Usually, the

analysis of thermoelectric devices, including the temperature-dependence of the material

properties and the electrical and thermal contact resistances, is very formidable. However,

when one uses the ideal equation with the effective material properties for moderate

temperature differences, the analysis becomes simple and robust and could be a platform

for optimal system design. The maximum temperature differences given by

manufacturers may not be consistent.

Normalized charts are constructed using the ideal equation and the maximum

parameters defined in this work. The normalized charts I and II represent well the

performance of any thermoelectric modules at a given dimensionless figure of merit.

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