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How does fluid loose temperature after leaving an expansion valve in a refrigeration cycle? Where does this heat go?

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  • $\begingroup$ Expand the gas takes work, and that energy has to come from somewhere. it coems from the thermal energy. $\endgroup$
    – DKNguyen
    Dec 13, 2023 at 19:39
  • $\begingroup$ Fun fact, not all fluids always get colder. Some increase in temp in certain kinds of expansion. It depends on how entropic the expansion is, what the starting temp and pressure are, and the composition of the gas. Joule Thompson Effect - en.wikipedia.org/wiki/Joule%E2%80%93Thomson_effect $\endgroup$
    – Phil Sweet
    Dec 14, 2023 at 0:36
  • $\begingroup$ the valve does not cool the fluid $\endgroup$
    – jsotola
    Dec 14, 2023 at 1:08
  • $\begingroup$ Why can your aerosol deodorant can get cold when you use it? Check out free expansion. $\endgroup$
    – Solar Mike
    Dec 14, 2023 at 6:58

2 Answers 2

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The "heat" didn't go anywhere.

The heat goes into making the gas expand, the same way that we had to put energy into the gas to previously compress it.

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  • $\begingroup$ This gives the impression that the process is mostly reversible. The expansion devices used in HVAC use non-reversible, highly entropic processes that are not related to compression work. $\endgroup$
    – Phil Sweet
    Dec 14, 2023 at 11:27
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Ideal Gas law "Guy Lussacs" law. When a pressure is exerted upon a working fluid, in a fixed volume it's temperature will change. When a gas is pressurized, thermal energy typically is applied into the system, when the volume increases as the fluid is ejected. Usually a fan or passive evaporative heat dissipator disposes of the waste heat.

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