A study of the reverse cycle defrosting performance on a multi-circuit outdoor coil unit in an air source heat pump – Part I: Experiments

Frost inevitably forms on the outdoor heat exchanger surface when its surface temperature is below both the dew point of air and the freezing point of water during ASHP heating.

“if the outdoor heat exchanger surface temperature is below both the dew point temperature of air and the freezing point temperature of the water, frost would inevitably generate on the surface of the outdoor heat exchangers when the ASHP system works in the heating mode [7,8].”

In open literature, most scholars regarded the total mass of melted frost as frost accumulation for further calculations.

“Therefore, in open literature, most scholars regarded the total mass of the melted frost as frost accumulation, to conduct further calculations [2,101,103,115,120,124,125].”

Initially, certain scholars did not take into account residual or retained water on the plate or fin surface, using only water-collecting trays under the heat exchanger for melted frost collection.

“Initially, certain scholars did not take into account the residual or retained water on the surface of the plate or the fins of the heat exchanger. Only water-collecting trays, located under heat exchanger, were used for the collection of melted frost in their defrosting experimental studies for ASHP units [101,120,125].”