6 Main Types of Expansion Valves: an Easy to Understand Guide from buzai232's blog

6 Main Types of Expansion Valves: an Easy to Understand Guide

Expansion valves are devices used to control the refrigerant flow in a refrigeration system. They remove pressure from the liquid refrigerant to allow expansion or change of state from a liquid to a vapor in the evaporator. Expansion valves serve two purposes: controlling the amount of refrigerant entering the evaporator and maintaining the pressure difference between the condenser (high-pressure side) and the evaporator (low-pressure side). In this article, Linquip will investigate the different types of expansion valves. Read on and find out more about them.Get more news about Condenser Expansion Machine,you can vist our website!

At Linquip, we can provide you with all the information you require to make an appropriate choice regarding expansion valve equipment based on your application or requirements. We at Linquip are eager to answer any questions you have about expansion valves. Start by reading this Linquip article entitled “What is Expansion Valve?“.
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1. Thermal Expansion Valves
A thermal expansion valve or thermostatic expansion valve (often abbreviated as TEV, TXV, or TX valve) is a device that controls the amount of refrigerant released into the evaporator and is intended to regulate the superheat of the vapor leaving the evaporator. Although often described as a “thermostatic” valve, an expansion valve does not regulate temperature; the temperature of the evaporator will vary with the evaporation pressure.

These types of expansion valves are popular due to their simplicity and availability, and their relatively good sensitivity and accuracy in regulation. The large choice of expansion valve sizes and bulb charges means the capacity and temperature ranges are very good. The disadvantage of TEVs is the necessity for relatively high superheating, which steals the heat transfer area from the evaporation process.
The TEV strives to maintain a stable level of superheating inside the evaporator under all conditions by adjusting the mass flow of refrigerant in response to the evaporator load. This is achieved by a membrane inside the valve housing, which compares the temperature before and after the evaporator. To be able to compare the pressures before and after the evaporator, the TEV has to be combined with another device, a bulb. The difference in pressure between the saturation pressure of evaporation and the pressure of the bulb is balanced across a membrane inside the head of the valve. The movement of the membrane controls the position of a needle and hence the mass flow of refrigerant entering the evaporator.

2. Manual Valves
These types of expansion valves are manually operated needle valves. The needle position is fixed, and the mass flow through it depends on the pressure difference across the valve. The hand expansion valve is normally used as a supplementary safety valve installed in a bypass line. It is also commonly used to control the flow rate through oil bleeder lines. The manual expansion valve is non-regulating and should not be used as an expansion valve with a BPHE evaporator, because any changes in operating conditions would instantly change the evaporation process inside the rapidly responding plate heat exchanger. Regulating the flow manually would require immediate adjustment, which is not practically feasible.​​

These types of expansion valves have the disadvantage of being unresponsive to changes in load or seawater temperature and must be adjusted frequently. The valve itself is a screw-down needle valve dimensioned to give fine adjustment.
3. Capillary Tubes
A capillary tube is a long, wound-up copper tube with a tiny opening that receives hot, high-pressure liquid refrigerant from the condenser. This small opening holds high pressure on one side of the tube and low pressure on the opposite side. The friction from the walls of the tube rapidly reduces the pressure of the refrigerant flowing through it.