Evaporator and Condenser role change

In a heat pump system, the role of the evaporator and condenser changes when it becomes heater from cooler. In summer time, it is a cooler, outside unit is the condenser, inside is the evaporator. But in winter time, the outside unit becomes evaporator and inside unit becomes condenser, the refrigerant moves at a different direction, that is, the refrigerant's moving direction is reversed when it becomes a heater from a cooler. The moving direction changes again when it becomes a cooler from a heater. However, the compressor can never change it refrigerant direction, that is the reason why heat pump system needs reverse value and many cases it also has a refrigerant accumulator in front of the compressor, the refrigerant accumulator is to make sure that no liquid will ever enter compressor.

The following is a AC system chart. not a heatpump system chart.

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