Effects of evaporator frosting and defrosting on the performance of air-to-water heat pumps

Frost, defrost, and refrost and its impact on the air-side thermal-hydraulic performance of louvered-fin, flat-tube heat exchangers

“…Verma et al [3] developed a quasi-steady, finite-volume model for frosting of plainfin-round-tube heat exchangers. Tassou and Marquand [4] and Machielsen and Kerschbaumer [5] did similar research on the effects of frosting and defrosting on heat exchanger performances. Yan et al [6] investigated the performance of frosted finned-tube heat exchangers with plain fins, single-bank louvered fins, and multi-louvered fins, and found that the heat transfer rate, the overall heat transfer coefficient, and the pressure drop for multi-louvered fins were higher than the others.…”

Performance evaluation of air-source heat pump based on a pressure drop embedded model

“…To mitigate these two negative effects, heat pumps are typically equipped with a defrosting mode, which can involve cycle reversal, hot gas bypass, or electric resistance heating. However, defrosting comes at a cost to the COP, as electricity is consumed without generating useful heat [ 27 ]. Modeling frost formation and defrosting is highly complex, and therefore, a defrosting mode has not been incorporated into the simulation.…”

Defrost improvement by heat pump refrigerant charge compensating

“…During the defrosting operation, the heat pump runs in the cooling mode. Once the reverse-cycle defrost is terminated, the heat pump is immediately switched back to normal heating operation [6]. Defrosting is thoroughly a major problem of concern for ASHP in winter.…”