Improvement Of Transient Supercooling Performance For Thermoelectric Cooler

Along with the appearance of semiconductor thaermoelectric material, thermoelectric cooler has been widely applied in many fields, such as health care, space missions, military, industry and so on. Compared with the traditional refrigeration technology, it has the advantages of small volume, fast response, no moving parts and environmental friendly. Generally a single-stage TEC can achieve an about 70 K maximum temperature difference between the cold and hot ends. In order to improve the cooling performance, more attention has been paid to its supercooling performance. In this paper, a three dimensional, multiphysics, and transient model is firstly developed. The model considers all thermoelectric phenomena occurred in the TEC and variable properties. This paper researches the effect of current pulse shapes, semiconductor shapes and two-stage TEC.This paper investigates various current pulses (t0,t1/2, t1, t2, t3, t4, t5) and studies the influence of pulse amplitude, pulse width and boundary conditions on the pulse supercooling. For a series of pulse shapes with the same pulse width, pulse amplitude, and boundary conditions, when Tc,min occurs at tmin<τ, a lower Tc,min can be achieved for the pulse shape with a higher power; on the contrary, when Tc,min occurs at tmin=τ, Tc,min becomes lower for the pulse shape with a lower power.A new design with variable semiconductor cross-sectional is adopted in this paper and it produces two additional effects.Firstly, the variable cross-sectional area makes the thermal resistance asymmetric, and hence Joule heat is preferentially conducted towards to the end with a larger cross-sectional area, referred to as the heat conduction effect. Secondly, more Joule heat is produced close to the end with a smaller cross-sectional area, named as the Joule heat effect. The Joule heat effect always dominates over the heat conduction effect during the pulse period; hence, more heat is transferred to the end that has the smaller cross-sectional area. However, this phenomenon is reversed after the pulse is terminated, and more heat is transferred to the end that has the larger cross-sectional area. As a result, when a lower minimum cold end temperature, a weaker temperature overshoot, and/or a longer holding time are/is required, the design with a larger cross-sectional area at the cold end should be adopted; when a shorter recovery needs to be preferentially considered, the design with a smaller cross-sectional area at the cold end is recommended.A novel concept design for thermoelectric cooler combining the advantage of two-stage structure and supercooling effect was firstly proposed. Compared with the single-stage TEC, the supercooling performance of two-stage TEC has a lower cold end temperature and longer holding time. For a separate two-stage TEC, when the pulse amplitude and width of hot stage is reasonably smaller than that of cold stage, the supercooling performance will be better. If a lower cold end temperature is required, the current pulse should be applied to the hot stage earlier; if a longer holding time is the highest-priority goal, the current pulse of hot stage should be started later.