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Research Papers

# Thermoelectric Performance of Novel Composite and Integrated Devices Applied to Waste Heat Recovery

[+] Author and Article Information
B. V. K. Reddy

e-mail: bvkreddy680@gmail.com

Matthew Barry

e-mail: mmb49@pitt.edu

John Li

e-mail: johnli407@yahoo.com

Minking K. Chyu

Leighton Orr Chair Professor and Chairman
e-mail: mkchyu@pitt.edu
Department of Mechanical Engineering and Materials Science,
University of Pittsburgh,
Pittsburgh, PA 15261

1Corresponding author.

Contributed by the Heat Transfer Division of ASME for publication in the Journal of Heat Transfer. Manuscript received March 2, 2012; final manuscript received September 25, 2012; published online February 11, 2013. Assoc. Editor: Zhuomin Zhang.

J. Heat Transfer 135(3), 031706 (Feb 11, 2013) (11 pages) Paper No: HT-12-1081; doi: 10.1115/1.4007892 History: Received March 02, 2012; Revised September 25, 2012

## Abstract

Thermoelectric elements, made of semiconductor slices laminated onto highly conductive interconnector materials, are termed composite thermoelectric device (TED). An integrated TED is a composite TED with the interconnector designed as an internal heat exchanger with flow channels directing the working fluid between the source and element legs. In this work, novel composite and integrated TEDs are proposed as an alternative to conventional TEDs, and their performance in terms of power output P0, heat input Qh, conversion efficiency η, and the produced electrical current I is studied using analytical solutions. The top and bottom surfaces of the TED are subjected to a temperature differential while the side surfaces are exposed to either ambient or adiabatic conditions. An increment in temperature differential results in enhanced device performance. For a fixed temperature differential, the integrated TED shows nearly an eight-fold increase in both P0 and Qh and a four-fold increase in I, whereas the composite TED shows approximately a two-fold increase in P0, Qh, and I when compared to the conventional TED values. Both novel TED designs have a minimal impact on efficiency predictions. However, an increase in semiconductor slice thickness resulted in an exponential decrease in P0, Qh, and I, and an exponential increase in η values and reaches a limit of conventional TED values. The effect of semiconductor slice thickness on η in the novel TEDs is remarkable when it is less than 1 mm. The change in ambient conditions via convective heat transfer coefficient has negligible effects on P0; however, a substantial change in η occurs when it is less than $100 Wm-2K-1$.

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## Figures

Fig. 1

Segment of a thermoelectric material

Fig. 2

Schematic of (a) conventional, (b) composite, and (c) integrated thermoelectric devices

Fig. 3

Effects of hot surface temperature on (a) electrical power output and (b) heat input for various TED designs (at h = 0 Wm-2K-1,Tc = 300 K, d = 5 mm, and RL = Ri)

Fig. 4

Effects of hot surface temperature on (a) thermal efficiency and (b) electrical current for various TED designs (at h = 0 Wm-2 K-1,Tc = 300 K, d = 5 mm, and RL = Ri)

Fig. 5

The temperature variation along the length of leg (L) for various TED designs at Th = 350 K and 500 K values (at h = 0 Wm-2K-1,Tc = 300 K, d = 5 mm, and RL = Ri)

Fig. 6

Influence of cold surface temperature on (a) electrical power output and (b) heat input for various TED designs (at h = 0 Wm-2K-1,Th = 450 K, d = 5 mm, and RL = Ri)

Fig. 7

Influence of cold surface temperature on (a) thermal efficiency and (b) electrical current for various TED designs (at h = 0 Wm-2K-1,Th = 450 K, d = 5 mm, and RL = Ri)

Fig. 8

The variation of (a) electrical power output and (b) heat input for different semiconductor slice thicknesses (at h = 0 Wm-2K-1,Th = 450 K,Tc = 300 K, and RL = Ri)

Fig. 9

The variation of (a) thermal efficiency and (b) electrical current for different semiconductor slice thicknesses (at h = 0 Wm-2K-1,Th = 450 K,Tc = 300 K, and RL = Ri)

Fig. 10

The response of (a) electrical power output, (b) heat input, and (c) thermal efficiency of TED designs with various convection heat transfer coefficients (at Th = 450 K,Tc = 300 K, d = 5 mm, and RL = Ri)

Fig. 11

The variation of (a) electrical power output and (b) thermal efficiency with load resistance (RL) for different semiconductor slice thickness (at h = 0 Wm-2K-1,Th = 450 K and Tc = 300 K)

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