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Homework Help: Thermodynamics: Vapor Compression Refrigeration that is Adiabatic?

  1. Apr 23, 2012 #1
    Consider a heat pump works on the vapor-compression refrigeration cycle with 0.2 kg/s of refrigerant-134a as the working fluid. The cycle is used to maintain a house at 26oC while absorbing heat from the outdoors at 3oC. R-134a enters the compressor at 200 kPa as a saturated vapor and leaves at 900 kPa, 50oC. The refrigerant leaves the condenser as a saturated liquid. Assuming the four devices to be well-insulated:

    I need to find COP, but in order for that i need QH, which i cant have because all the devices are insulated. How do i proceed?
  2. jcsd
  3. Apr 26, 2012 #2
    COP (heating)=Q-hot/W-net,in

    COP (heating)=M-dot * (h2-h4)/m-dot * (h2-h1)

    Pt 1: 200 kPa,3 C
    Pt 2: 900 KPa,50 C
    Pt 4: 900 KPa, 26 C

    See if that works
  4. Apr 26, 2012 #3

    Pt 1:200 kPa, sat. Vapor, -9 C

    Pt 2: 900 kPa, 50 C

    Pt 4: 900 kPa, sat. liquid, 35.4 C

    Find enthalpy' s for various points, use equation for COP-heat
  5. Apr 27, 2012 #4
    Thank you
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