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The transient supercooling enhancement for a pulsed thermoelectric cooler (TEC).

Number: pap. 2473

Author(s) : MAO J., DU J., WANG S., et al.

Summary

Once TEC excitated by a high-voltage pulse, there exists a transient thermoelectric supercooling effect, which can be enhanced by keeping on increasing the Peltier cooling effect to compensate for the negative self-heating from the Joule heating effect and Fourier heat conduction effect. After superimposing an additional voltage pulse over a steady-state reference value in a short time scale, abrupt temperature drop will be produced by several more degrees below the steady-state cold junction temperature, and even against the earlier arrival of excessively Joule heating-dominated heat accumulation at cold junctions. Most previous work mainly focused on the minimum supercooling temperature or the maximum supercooling capacity achievable for a conventional thermoelectric module based on bismuth-telluride alloys. Nevertheless, three key process control parameters, with respect to the system response time for the supercooling temperature, the holding time of the supercooling state and the recovery time back to the reference steady state, were almost overlooked. In this work, analytical solutions on the optimization of pulse shapes upon the thermal-electrical conversion mechanism were investigated, for exploring the dynamic behaviours of the main thermoelectric effects respectively on the transient response for the cold junction temperature drop and the supercooling enhancement degree during pulsed operation. Furthermore, by the combinatorial optimization of the above process control parameters and pulse shapes, the optimal characteristic parameters for TE devices pulsed with supercooling are derived. The results indicate that, the monotonically increasing quarter-wave pulse shapes (especially the quarter-sine voltage excitation), combined with the optimized pulse amplitude of 2.5 times and pulse duration of 10s, show a greater advantage to achieve high sensitivity and stability, and require less energy to reach the minimum temperature. Also, it has contributed to an increase on the effective Figure-of-merit ratio of ZT ZT eff from the previous value of 1.76 to a maximum of 2.06 (namely improved by 17% ), as well as smaller temperature differences between hot and cold junctions. The discussions can be served as a theoretical basis for a pulsed TEC to improve the additional supercooling effect, and also prevent extensive heating of the material after the minimum temperature is reached, which may be attractive for compact thermal system to come up to the localized cooling level of high power packaging.

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Pages: 11 p.

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Details

  • Original title: The transient supercooling enhancement for a pulsed thermoelectric cooler (TEC).
  • Record ID : 30019020
  • Languages: English
  • Source: 2016 Purdue Conferences. 16th International Refrigeration and Air-Conditioning Conference at Purdue.
  • Publication date: 2016/07/11

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