Structural optimization simulation of collector/evaporator for hybrid heat source heat pump

In order to improve the performance of the direct-expansion solar-air source heat pump water heater, the structure of the heat collector/evaporator needs to be optimized. Based on the existing experimental equipment, one-dimensional steady-state heat transfer mathematical model of the heat collector/evaporator and a heat pump system model were established. The accuracy of the models was verified by experiment. The heat collection efficiency calculated by the model was used as evaluation index, and the influence of the structural parameters on the thermal performance of the heat collector/evaporator was analyzed by orthogonal test and numerical simulation. The heat collection per unit fin area was selected as the economic evaluation index, and the heat collection performance was compared to determine the appropriate heat exchange area for the optimal structure at different heat exchange areas. Using the typical meteorological year parameters in Nanjing, 9 structures were selected at the same total heat exchange area on the air side. The heat collection efficiency of the heat collector/evaporator with different structures and the annual energy utilization of the system were calculated by simulation. The results show that the fin spacing, the inner diameter of the copper tube and the fin height have the greatest influence on the heat collection efficiency, and the influence of three structural parameters is consistent within a certain range. The heat collection efficiency can reach the maximum value in the selected range. As the total heat transfer area of the fins increases, the total heat resistance on the air side gradually decreases, and the total heat collection amount of the fins gradually increases. The heat collected per unit fin area can get maximum amount at 13.22 m2, with can increase the heat collection of the heat collector/evaporator and is economical. Under different seasonal operating conditions, the optimization effect is the best when the total heat exchange area on the air side is 13.22 m2, the inner diameter of the copper tube is 9 mm, the fin spacing is 1.7 mm, and the fin height is 10.3 mm. Compared with the original structure, the heat collection efficiency increases by 11.77%, and the annual energy efficiency ratio of the system increases by 9.36%. © 2020, Central South University Press. All right reserved.