Expansion Valve: Description and Operation

Expansion Valve







The expansion valve -B- restricts and regulates refrigerant flow, thus lowering refrigerant temperature and pressure as it flows to the evaporator.
The TT uses a thermo-dynamic expansion valve design. It regulates refrigerant flow as follows: As cooling demands increase (high outside temperatures), the temperature of the refrigerant leaving the evaporator and entering the expansion valve also increases. Here, the refrigerant temperature is sensed by a gas filled thermo-pressure chamber inside the expansion valve. The thermo-pressure chamber acts on a membrane attached to a conventional ball/orifice valve positioned in the expansion valve refrigerant circuit from the condensor to the evaporator. As the refrigerant temperature increases, the thermo-pressure membrane opens the ball/orifice valve, allowing an increase in refrigerant flow to the evaporator. Increased cooling capacity is achieved as a result. As the refrigerant temperature exiting the evaporator decreases, the thermopressure membrane closes the ball/orifice valve, and restricts refrigerant flow to the evaporator. This cycle ensures consistent cooling efficiency, regardless of outside temperature.


NOTE:
- Always ensure that the expansion valve insulation is in place and is not damaged.
- Due to the thermo-dynamic design of the expansion valve, the operating parameters of the valve are adversely affected when the insulation is missing or improperly installed. A decrease in cooling efficiency will result.