Structure Design And Experimental Verification Of Thermal-electric Conversion System Based On PCMs

Hypersonic vehicles will be large amounts of aerodynamic heat due to high speed friction in dense atmospheres.At present,no material can withstand these loads during the mission process,which puts forward higher requirements for the thermal management system of the aircraft.Based on thermoelectric technology,a new thermal-electric conversion system is proposed for the thermal protection task of environmental control and heat management system of hypersonic vehicles.The system collects the aerodynamic heat flow with phase change materials and constructs a stable temperature gradient.Then thermal energy is converted into electrical energy through thermoelectric generator,which directly drives the thermoelectric cooler to partially cool the electronic equipment with high heating power in the cabin.The heat transfer is effectively transferred in different spaces of the spacecraft while reducing the surface temperature of the hypersonic vehicle,thereby realizing the application of heat conversion.For this thermal-electric conversion system,the ANSYS software is used to simulate the thermoelectric device.The effects of temperature difference,ZT value,load resistance and input current on the performance of the thermoelectric device is studied.The inverse push method is used to analyze the thermal-electric conversion system.The results show that the precise temperature control of thermoelectric cooler can be achieved by adjusting the temperature difference between the two sides of the thermoelectric generator or changing the number of p-n junctions.Since the fundamental performance of thermoelectric devices cannot be maximized under the same conditions at the same time,it needs to be optimized.Taguchi optimization method is used for single-objective optimization analysis of thermoelectric devices.Response surface method is used for multi-objective optimization of thermoelectric devices,and the optimized parameters are simulated and verified.Based on the thermal resistance model,the relevant parameters are dimensionless,and the energy conservation law is utilized to derive the parameter expressions of the output power and conversion efficiency of the thermal-electric conversion system.The results show that when the thermal resistance of thermoelectric device is greater than the equivalent thermal resistance of phase change materials,the output power and efficiency of the thermal-electric conversion system can reach the best at the same time,which provides theoretical guidance for structural assembly and experimental evaluation.Expanded graphite/paraffin composites and expanded graphite/erythritol composites required for the integrated system are prepared by vacuum impregnation method,and the related properties are characterized.By calculating and analyzing the total energy and average conversion efficiency of the system in finite time,it is concluded that the energy conversion system is more suitable for high frequency fluctuating load conditions,which provides a new design idea for the environmental control and thermal management of hypersonic vehicles.