Valve Control Logic Impact on Defrost Cycle Operations in Cold Start Conditions

This study investigated the behavior of a residential heat pump during defrost cycle operation under cold start operating conditions. One promising approach consists of implementing intelligent valve control strategies that dynamically modify the hydraulic configuration of the heating system during the defrost cycle. Instead of permanently increasing the water volume through the installation of a buffer tank, additional heating zones can be temporarily activated during the defrost period in order to increase the circulating water volume and provide additional thermal support. Several simulation scenarios were analyzed in order to understand when the available thermal energy in the hydraulic circuit can guarantee the success of the defrost process. The results highlight an important aspect of defrost cycle operation that was not fully evident in previous analyses.