Experiment investigation of reverse cycle defrosting methods on air source heat pump with TXV as the throttle regulator

Reverse-cycle defrosting technique is one of the simplest and most widely used defrosting methods for air source heat pumps (ASHP). However, there are still some problems if thermal expansive valve (TXV) is used as throttle regulator in the unit: the defrosting process might last so long that users would feel uncomfortable due to the fluctuation of the indoor temperature: the system cannot resume heating mode smoothly after the defrosting process, the system often breaks down due to the triggering of low-pressure switch. In this paper the authors proposed that these two problems can be greatly relieved if there is a by-pass solenoid valve in the system which can by-pass the TXV used in the defrosting mode, and best performance can be addressed if the by-pass valve is energized during the whole defrosting process.