What type of thermostatic expansion valve is typically used in refrigeration systems involving an evaporator with a refrigerant distributor?

The externally equalized thermostatic expansion valve (TEV) is typically used in refrigeration systems that incorporate an evaporator with a refrigerant distributor because it allows for more accurate control of refrigerant flow in systems with varying conditions. In these systems, there can be significant pressure differences between the evaporator inlet and outlet due to the use of a distributor, which can affect the performance of the valve.

By utilizing an external equalization connection, the TEV can more accurately sense the pressure downstream of the evaporator. This capability helps to ensure that the valve opens and closes appropriately, reacting to changes in pressure and ensuring optimal refrigerant flow to meet the evaporator's cooling load efficiently. This adaptability is vital, especially in systems where multiple evaporators or varying loads are involved.

Internally equalized valves, while suitable for simpler systems, may not perform as well under the conditions found in systems with refrigerant distributors, as they cannot accommodate the pressure variations effectively. Electronic expansion valves and fixed orifice valves serve different purposes and applications within refrigeration and HVAC systems, but are not primarily associated with systems that utilize distributors. Therefore, the design and functional requirements of the system strongly favor the use of the externally equalized TEV in this context.