Structural optimization of collector/evaporator of direct-expansion solar/air-assisted heat pump

In cold regions, traditional air source heat pumps are easily frosted in heating state. The frosting problem can be effectively overcome by the direct-expansion solar/air-assisted heat pump (DX-SASIHP). One of the most critical components in the DX-SASIHP system is the collector/evaporator, whose performance hinges on its structure and material. To improve the heating performance of DX-SASIHP, this paper attempts to optimize the structure and material of the collector/evaporator by the Computational Fluid Dynamics (CFD) method. Specifically, key parameters like tube diameters, rib height, rib thicknesses, and tube material were examined under the same weather conditions. On this basis, the heat collection capacity and heat collection efficiency of the collector/evaporator were evaluated. Finally, the collector/evaporator structure was optimized in the light of heat collection capacity, heat collection efficiency and manufacturing cost. The key parameters were optimized as follows: 23 mm for tube diameter, 45 mm for rib height, 4 mm for rib thickness, and aluminum for tube material. The research results lay a theoretical basis for the collector/evaporator design of DX-SASIHP in heating state. (C) 2020 The Authors. Published by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University.