Transient Characteristics Of Pulsed Supercooling For Microscale Thin-film Thermoelectrics

In recent years,the power consumption of electronic components increases and the size decreases,which leads to the increasing heat flux of micro electronic devices.The traditional bulk thermoelectric refrigerators have been unable to meet the demand.Micro scale thin-film thermoelectric coolers has the advantages of small volume,and the characteristics of electronic components integrated is not affected by the volume limit.They can satisfy the cooling requirement of large power density of electronic devices,especially suitable for cooling and temperature control of micro electronic devices.It has become a research hotspot in the field of thermoelectric refrigeration.In this thesis,a multi-physics coupling model of a thin-film thermoelectric refrigerator is established by using COMSOL Multiphysics simulation software.And the Thomson effect is considered.The transient supercooling characteristics of four pulse shapes : step?isosceles?ramp up and ramp down are studied.Compared the temperature change trend of different pulse amplitude and different pulse width,then change the thermoelectric arm length,the convective heat transfer coefficient of the hot end and cooling load.And also,the effects of the variation of P and N physical properties and contact resistance are considered.The simulation results show that the response time of the thin-film thermoelectric unit is within 1ms,which is different from the traditional bulk thermoelectric coolers.The four kinds of pulse shapes can instantly increase the cooling effect of the thermoelectric cooler.When the 4mA pulse current is applied,the supercooling temperature difference can reach 9K,which is 9 times of the steady-state temperature drop.Pulse shapes which is high at the begining,then slowly decreasing has better supercooling performance.And the larger the pulse amplitude,the lower the minimum temperature that the cold end can achieve.But at the same time,the highest temperature will also increase correspondingly,and the recovery time will increase too.This thesis also applies the thin-film thermoelectric cooler to the heat dissipation of millisecond laser.The results show that after applying the step shape pulse which is 2 times steady current,the cooling effect is increased by 69% compared with the constant current.The continuous pulse can effectively reduce the temperature of the laser chip,so as to ensure the normal operation of the laser.When the continuous pulse is applied,the supercooling temperature difference decreases slightly after the first pulse,but with the increase of the pulse number,the temperature of the chip will change periodically.