After the refrigerant loses heat in the condenser, it temperature falls. It becomes a liquid from gas. It then leaves for the evaporator coil for another cooling cycle. But before it reaches the evaporator coil it goes to expansion valve. The valve expands the refrigerant so it loses pressure, causing its temperature to further drop. The valve also controls the rate at which the refrigerant enters the evaporator coil: It works to coordinate between the flow rate of refrigerant the evaporator and the rate at which the refrigerant “burns off” in the evaporator coil as it absorbs heat. This ensures the best possible energy efficiency. This is very important. If too much refrigerant reaches the coil and does not burn off, then a partial amount of refrigerant in liquid form will go to the compressor. This can cause expensive damage to the compressor.