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HEAT PUMP
Liquid receiver
The refrigerant charge of the unit depends from the heat exchanger capacity. For a reversible heat pump the heat
exchangers work as condenser or as evaporator, in accordance to the cycle. The liquid receivers are installed on the
refrigerant circuit and allow to store the charge difference between the two cycles.The placement of the liquid receiver
shall be evaluated depending on the capacity of the heat exchangers of the plant and those installed on board of the unit.
For example:
Capacity of the heat exchanger on board: 10 liters
Capacity of the Remote heat exchanger: 6 liters
During chiller operating mode the heat exchanger on board works as a condenser, while the remote one works as
evaporator. Viceversa during heat pump mode. The difference between the capacity of the two heat exchangers results
in a refrigerant charge difference between the two cycles, it is therefore necessary to have a liquid receiver which
capacity shall be properly sized to store the excess of refrigerant when a smaller refrigerant charge is required.
Liquid receiver sizing
Here below an evaluation method for the liquid receiver sizing is shown. The described method is proposed to give an
approximate indication for the selection of the proper liquid receiver. The volume values obtained may change depending
on the specific plant requirements and shall therefore be evaluated in the plant design.
VReceiver= 0.4x( V1 – V2 )
V1: volume of the unit's heat exchanger (please contact Trane to obtain this information)
V2: Volume of the remote heat exchanger.
If V receiver has positive sign, the receiver shall be placed so as to be filled in heat pump mode and discharged in chiller,
otherwise it shall be placed so as to be filled in chiller mode and emptied in the heat pump.
In addition, the liquid receiver capacity shall be sized in accordance to the total refrigerant charge of the plant, in order to
store the entire amount of refrigerant in the plant in case maintenance.
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