Whats inside a thermal expansion valve and how the thermostatic expansion valve or TXV works in a HVAC refrigeration system and the basic working principles that allow it to meter the flow of refrigerant into the evaporator of chillers and ac units.
source/image(PrtSc): The Engineering Mindset
A thermal expansion valve or thermostatic expansion valve is a component in refrigeration and air conditioning systems that controls the amount of refrigerant released into the evaporator and is intended to regulate the superheat of the vapor leaving the evaporator. Watch the video from The Engineering Mindset for more info:
The superheat is the excess temperature of the vapor above its boiling point at the evaporating pressure. If there is no superheat it indicates that the refrigerant is not being fully vaporised in the evaporator and liquid may end up recirculated to the compressor, an excessive superheat indicates that there is insufficient refrigerant flow to chill the entire evaporator.
Therefore by regulating the superheat to a small value, typically only a few °C, the heat transfer of the evaporator will be near maximal, without excess un-evaporated refrigerant being returned to the compressor.//wikipedia