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Homework Help: Refrigeration Heat Exchanger Area Ratio Optimization

  1. Aug 6, 2013 #1
    The equation for heat transfer is:

    1. Q = U.A.(TL-T1)


    Q= heat transfered (W).
    U= overal h.t. coefficient.
    A= area of heat exhanger (m^2).
    TL= Temp. of refrigerated space (Kelvin)
    T1= Low temp. of refrigerant= refrigerant in evaporator (K)

    I want to eventually find the maximum heat removed from the refrigerated space: QL, corresponding to the optimal heat exchanger area ratio: Xa.

    2. QL,max. = Capture11.jpg (Click for clear version)

    3. Xa,optimum = Capture22.png

    I know all values in parts 1. 2. and 3. except for A, U and QL,m(QL max).

    My question:

    I want to find a reasonable value for A and U (the values will be theoretical but must be realistic, and I only need these results so I can show how using a optimised area ratio will improve them). After that I will optimize the system using the QL max and Xa optimum equations, from 2. and 3. above, respectively. Does this make sense to you? I have many doubts, such as when I sub in a reasonable value for A, I do not find a reasonable value for U, even though I trust my other values are correct.

    What other equations for U are there, so I might be able to find this oppose to estimate?

    Thanks for your time
    Last edited: Aug 6, 2013
  2. jcsd
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