What is an expansion valve in refrigeration?
A thermostatic expansion valve (TXV) (see Figure 1) is a refrigeration and air conditioning throttling device that controls the amount of refrigerant liquid injected into a system’s evaporator—based on the evaporator outlet temperature and pressure—called the superheat.
What does an electronic expansion valve do?
The electronic expansion valve (EEV) operates with a much more sophisticated design. EEVs control the flow of refrigerant entering a direct expansion evaporator. They do this in response to signals sent to them by an electronic controller. A small motor is used to open and close the valve port.
How many types of expansion valve used in refrigeration system?
Types. There are two main types of thermal expansion valves: internally or externally equalized. The difference between externally and internally equalized valves is how the evaporator pressure affects the position of the needle.
How do you choose an expansion valve for refrigeration?
The following procedure helps to select the correct valve for the system.
- Determine the pressure drop across the valve.
- Determine required valve capacity.
- Determine required orifice size.
- Select a thermostatic charge.
- Determine if external equalizer is required.
- Order the required components.
What is the difference between a TXV and an Exv?
The electronic expansion valve (EXV) could be the newest addition. In a conventional TXV system, the TXV senses pressure/temperature at the evaporator outlet, and uses the amount of superheat (heat added to the refrigerant after it has vaporized) to determine the correct refrigerant flow at the evaporator inlet.
How do refrigeration valves work?
The gauge port is closed and the valve is open, allowing refrigerant to flow through the system. If the valve stem is all the way in, the valve is considered to be in the front-seated position. This allows the refrigerant to flow through the system and the system pressure to be read through the gauge port.
How do I adjust my refrigeration expansion valve?
Locate the adjustment needle on the thermostatic expansion valve. Turn the adjustment needle one quarter turn counterclockwise to decrease the temperature. Each quarter turn is equal to one degree. Turn the adjustment needle a quarter turn clockwise for each degree needed, to increase the temperature.
How do I choose an electronic expansion valve?
How to select the correct Electronic Expansion Valve?
- Showcase/Evaporator capacity.
- Pressure drop across the valve. a. Δp,valve = pc – (pe + Δp1 + Δp3 + Δp4)
- Correction for sub cooling. a.
- Correction for evaporating temperature. a.
- Determination of valve size.
- Correctly dimensioned liquid line. a.
What size TXV do I need?
That means you can find: A TXV for 1.5 to 2 ton systems. A TXV for 2 to 3 ton systems. A TXV for 3.5 to 5 ton systems.
