Investigation On Energy Transport For Peltier-effect Thermoelectric Module And Its Application To Thermal Design

With the rapid development of IT and life science,reliability of the devices is greatly dependent on the cooling technology.Thermoelectric cooler（TEC）is a solid-state refrigeration,without any moving parts and refrigerant.It can be easily integrated with other devices,and is employed popularly in the thermal management system.The temperature can be precisely controlled by adjusting the inputted current and voltage of TEC,which leads TEC is significantly important in the thermal management field.There are two key points in thermoelectric cooling applications.One is how to prepare high efficient TEC module using existing thermoelectric material,the other is how to effectively use the TEC module in the thermal management system.Currently,the classical thermo-electric conversion theory developed by Ioffe is employed to evaluate the performance of TE material and optimize the thermoelectric equipment.However,the theory just considers thermo-electric conversion of TE material,and energy transport beside of TE material in the thermoelectric module is not considered.As a result,TE material cannot be effectively used.Based on the above analysis,the main works of this research are summarized below.Firstly,the complete energy transport process for TEC is investigated.A complete modified model（analytical solution）for TEC has been developed.Energy transports caused by substrate,air gap and the interface between TE material and connector,are determined.Experimental setup is developed to determine the electrical contact resistivity of commercial TEC.Three-dimensional（3D）Multiphysics model for TEC is developed.An experimental test bench is built to validate the 3D model.These energy transport processes are investigated using the 3D model.It is found that the effect of heat transfer between side surfaces of the legs and air gap can be neglected.Based on this conclusion,the 3D model can be derived into modified model.It is found that the results between the 3D model and modified model are almost identical at effective working range(I<I_max).The deviation of cooling capacity between the 3D model and modified model for single-stage TEC is lower than 10%,and that is lower than 5%with respect to two-stage TEC.Secondly,parametric study for TEC is carried out based on the modified model.The optimum working conditions and geometric parameters for single and two stage TEC are determined at given conditions.The performances of four kinds of TECs,including ALO TEC,Au-Ni TEC,AlN TEC and vacuum TEC,are investigated.It is found that the optimum length of leg is 0.58mm at W_leg=1.50mm and number of thermocouples is 630 mm,when T_c=0^oC,T_h=30^oC and F=0.36.The performance of TEC can be improved by increasing F.It is unnecessary to vacuum TEC.The substrate with low thermal conductivity significantly decrease the performance for high cooling power TEC.Thirdly,the thermal design of thermoelectric cooling equipment is investigated.Thermoelectric cooling equipment consists of TEC,cold side heat sink and hot side heat sink.The performances of three types cooling devices,including passive cooling device,single-stage cooling device and two-stage cooling device,are investigated under different cooling temperatures,heat sinks and structure parameters.It is found the passive cooling method and single-stage TEC cooling method can be used when T_j is higher than T_a.Single stage TEC cooling and two-stage TEC cooling method can be used when T_j is lower than T_a.As T_c and T_h are changed,the variety magnitude of cooling capacity for passive cooling device is largest in the three cooling devices while that for the two-stage cooling device is smallest.Two-stage TEC can be used in low T_j and large thermal resistances of hot and cold heat sinks.There also exists optimum n and G factor in thermoelectric device at given conditions.The n and G increase with the increasing of T_j and decreasing of R_c and R_h.The cooling capacity also significantly increases.Lastly,thermoelectric device is innovatively used in IEF and CPU cooling system.The high efficient TEC device is designed to be used in the two systems based on the above conclusions.A two-stage TEC device is used in the IEF device to achieve lower focusing temperature（10^oC）while the commercial IEF device（GE Ettan IPGphor 3 and Bio-rad PROTEAN i12）could not achieve that focusing temperature.Phase change heat transfer and capillary phenomenon are employed to match the heat flux between cooling plate in IEF and TEC.The largest temperature difference along the cooling plate is lower than 1.0^oC.The COP of this cooling system is up to 2.0 under traditional focusing temperature（20^oC）.A high cooling power AlN based TEC is used in CPU cooling device.The water cooling device is used to cool the hot side of the TEC.The temperature control strategy with self-cooling is developed for the TEC device to prevent dew produced on CPU due to its various working conditions.It is found that the largest temperature deviation for the CPU is lower than1.4^oC at various conditions under severe environment.Moreover,little electrical power consumption when T_a and Q_g is low due to self-cooling.