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Thermostatic expansion valves control the flow of liquid refrigerant into an evaporator and keep air conditioning units running smoothly.
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Control: Accuracy, Maintained Over a Wide Variation in Evaporator Load, Thereby Minimizing Hunting Flood Back and Coil Starving Problems , Type: Adjustable
Thermostatic expansion valves, often abbreviated as TXVs, TEVs or TX valves reduce refrigerant pressure from the condenser pressure to the evaporator pressure. These valves keep the evaporator active as they increase the flow of refrigerant at high capacity loads and reduce the flow at low capacity loads. Thermal expansion valves provide complete evaporation of liquid refrigerant in the evaporator, thus eliminating liquid slugging. Thermal expansion valves can tolerate variation in refrigerant charge, as they adapt the refrigerant flow for matching the heat load. These valves minimise coil starving & flood back problems by controlling accuracy.
Uses
Parker Thermostatic expansion valves are used for regulating the flow of liquid refrigerant into an evaporator in aerospace, fluid & gas handling, hydraulic, filtration, sealing, shielding and process control applications.
Working Mechanism
The high-pressure liquid refrigerant is held back from the condenser by the valve. The valve regulates how much refrigerant can enter the evaporator. The valve decreases the pressure, allowing the refrigerant to boil at decreased temperatures. As the refrigerant is exposed to more thermal energy while passing through the evaporator, it undergoes a complete phase change and becomes a saturated vapour while reaching the end of the evaporator coil. During this change, there is almost no temperature change due to latent heat. Instead, there is an increase in entropy and enthalpy. The refrigerant continues picking up thermal energy and after the phase change, it begins increasing the temperature, thus superheating the refrigerant vapour. This temperature is monitored by the sensing bulb of the expansion valve to control the refrigerant in the main body of the valve.
Features
SC(E) Series valves are used in freezers, walk-in coolers, salad bars and ice machines. They feature brass body construction for excellent corrosion resistance. These valves have a balanced port design that maintains the refrigerant flow level in low ambient conditions. They are equipped with a removable inlet strainer for filtering contaminants out of hydraulic fluids. These thermostatic expansion valves utilise field adjustable superheat steam to minimise the risk of damage caused by carbonic acid corrosion or erosion.
EBSE Series valves provide extended ODF connections for excellent control in both flow directions.
Parker H / HC Series thermostatic expansion valves are ideal for use on heat pumps and air conditioning systems. These H / HC Series valves have a power element made of stainless steel for resisting corrosion on exposed surfaces and bleed ports for releasing pressure from the hydraulic system. HC valves are equipped with an internal check valve to protect equipment against backflow damage. These HC Series valves add an in-built, 5-ton check valve for R-407C, R-22 and R-410A heat pump applications, with either field-adjustable or factory-set superheat.
Installation
Locate the adjustment needle on the thermostatic expansion valve and turn the adjustment needle one quarter anticlockwise, to decrease the temperature.
Each quarter turn is equivalent to one degree.
Turn the adjustment needle 90 degrees clockwise for each degree required, to increase the temperature.
Frequently Asked Questions
What happens if the superheat is too high?
If superheat gets too high, it can increase the heat of compression, thus increasing temperature at the discharge valves. If the temperature elevates beyond its safe operating range, it may cause damage to the compressor.
How to adjust thermostatic expansion valves?
These thermostatic expansion valves are not adjustable in the open or closed positions as these are modulating valves. Turning the adjustment stem, whether in the clockwise or anti-clockwise direction, only increases / decreases the superheat.
Where are thermostatic expansion valves used?
These thermostatic expansion valves are utilised in systems such as packaged air conditioners, industrial refrigeration plants, central air conditioners and high capacity split air conditioners.
