Cooling effect of liquid throttling expansion
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I would like to ask everyone why the cooling effect is not significant when a liquid expands through a throttle valve. Furthermore, after isentropic expansion in a gas expander, the temperature drops and the enthalpy decreases; the reduced enthalpy is converted into mechanical work through the shaft. Hydraulic turbines also output work, with a corresponding decrease in enthalpy – so why isn’t the temperature drop significant? ? ? ?
“Why is the cooling effect not significant when a liquid expands through a throttle valve? ”This is the case for liquids with a large degree of supercooling. It is preferable to incorporate considerations regarding “thermal energy”; it’s better to understand it through the output of energy conversion, for reference.
Because gas expands after throttling, what about liquid throttling? Does not expand. Macroscopically, liquids are incompressible; therefore, they do not expand
Throttling expansion is a phenomenon associated with gases; the Joule-Thomson effect applies to liquids. Liquids are incompressible, and throttling merely increases the flow resistance without causing any expansion
The effect you mentioned is mainly used in refrigerators and air conditioners: throttling for expansion to cool down, and pressurization for liquefaction to raise temperature. However, not all liquids can be used as working fluids for refrigerators and air conditioners; you can consider the properties of the medium
The turbine does work, and its power source is the pressure of the water outside the system boundaries; this pressure pushes the water within the system to rotate the turbine. This type of work is known as displacement work, and it is completely different from the consumption of internal energy that occurs during the adiabatic expansion of gases. This explanation should make it easier to understand.
Throttling expansion for cooling is a gas-related phenomenon; liquids are incompressible. Throttling expansion of gases is currently primarily used in cryogenic applications such as air separation, liquid nitrogen washing, carbon dioxide handling, and LNG projects
If the Joule-Thomson coefficient is known, how to calculate the temperature after pressure reduction