Fin thermoelectric cooler performance characterization
Creamer, Patrick Lawrence
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Thermoelectric coolers (TECs) are attractive cooling devices because they have no moving parts and operate without the use of global warming potential (GWP) refrigerants. However, due to a low coefficient of performance (COP) and high system costs, TECs are limited to niche applications such as wine coolers, medical refrigerators, and luxury car seats where cost and efficiency are insensitive. Most thermoelectric (TE) research has been focused on improving TE material properties while neglecting the impact of device architecture on performance. However, recent research indicates that device architecture plays a significant role in device performance. Herein, the extent to which device architecture can improve performance is investigated, specifically via the integration of the thermoelectric elements into the heat exchanger. By shaping the TE material into a blade, the portion of the TEC leg above ambient temperature can function as a heat exchanger fin, effectively eliminating one of the most expensive parts of a TEC module. Further, insulation enclosing the outer surface of the fin that is below ambient temperature inhibits inadvertently absorbing heat from the environment and maximizes the cold side heat flux (qc"). Key questions that are investigated are the impact of enabling convection off the surface of a TE blade, the effect of current density, and the effect of device geometry (i.e., fin length, width, and insulation length) on qc" and COP. It is demonstrated that qc" converges to a maximum as fin length (L) increases, representing a departure from conventional flat-plate TECs. Further, by enabling convective heat transfer from the TE fin, only Joule heating and conduction heat transfer in the insulated region detracts from qc". Finally, a design strategy consisting of numerous closed-form expressions that identify key geometric dimensions that maximize qc" is developed.