Resistive-heating-based defrosting performance of carbon fiber-reinforced composite based fin for potential heat pump system

The frosting in the outdoor evaporators in air source heat pump systems (ASHPs) significantly affects their thermal efficiency, necessitating frost retardation methods. To address this issue, carbon fiber-reinforced polymer (CFRP) fin-based heat exchangers, which exhibit resistive heating behavior were prepared using polyacrylonitrile and pitch-based carbon fibers for potential applications in ASHPs to realize defrosting effects. Heat exchanger units with CFRPs fins were prepared for evaluating its resistive heating, frosting, and defrosting performances under various applied heat flux densities. Ambient temperatures of 0 and 5 °C and relative humidities of 70, 75 and 80 % were maintained under natural convection conditions; further, a low defrosting energy of 65 % was achieved in resistive heating when compared with that achieved using hot refrigerant defrosting. A hybrid_CFRP fin was prepared with a sandwiched graphite fin to enhance thermal conductivity, and its resistive heating was compared. Almost 168 % higher heat generation was observed in hybrid_CFRP fin compared to simple CFRP with enhanced conductive path. Further, air side heat transfer rate was greatly enhanced for Hybrid_CFRP units compared to the simple CFRP with a total 113 % higher rate, which indicates enhanced thermal performance.