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Homework Help: Expansion valve question

  1. Oct 27, 2011 #1
    1. The problem statement, all variables and given/known data
    Refrigerant 134-a enters the expansion valve of a refrigeration system at 160 psia as a saturated liquid and leaves at 30 psia. Determine the temperature and internal energy changes across the valve.


    2. Relevant equations

    Δu=cv*ΔT

    3. The attempt at a solution

    I'm not sure how to get the temperature change. Since we know it is initially a saturated liquid, I was able to get the initial temperature from a property table to be 109.5 °F

    Is there a way to tell if the refrigerant is a saturated mixture or a superheated vapor after the pressure change? Can we assume its a saturated mixture?
     
  2. jcsd
  3. Oct 27, 2011 #2
    Hint: Is there any work being done? Think first law for a flow situation.
     
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