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Adiabatic heat exchanger problem

  1. Oct 7, 2006 #1
    Adiabatic heat exchanger problem... Please Help!

    I have this proplem as a homework assignment and i'm a bit stuck as houw to set it up. Here it is:

    Propane gas enters a continuous adiabatic heat exchanger at 40 degrees C and 250 kPa and exits at 240 degrees C. Superheated steam at 300 degrees C and 5.0 bar enters the exchanger flowing countercurrent,y to the propane and exits as a saturated liquid at the same pressure.

    I know how to draw the process flowchart, but the problem also asks to include in the labeling the mass of the steam fed (kg). I have no idea how to figure this out. Is it in some table, or chart?

    Please Help, 'cause i am stumped!

    -Thanks in advance...
  2. jcsd
  3. Jan 9, 2007 #2
    Adiabatic heat exchanger

    Couple of questions for you: Do you own a copy of the si steam tables? Are you familiar with heat balances?

    Ok, i will try and point you in the right direction .

    Q= Of the steam = Q of the water

    Thus Q=McpDT m= mass of water/steam Kg Cp=Specific heat Dt= (Outlet Temp - Inlet)

    So call steam 1 and Water 2


    OR we can say that Q=m*Hf-Hg and take the data from the steam tables for steam as we know the conditions in and out! once we know Q ofcourse....lol ( H is Empalthy)

    Good luck , hope this is some help....half asleep so probs wrote crap! lol :rofl:
  4. Jan 11, 2007 #3
    i didn't mean water i meant propane....lol
  5. Jan 14, 2007 #4


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    The problem seems to relate to the Joules-Thompson effect.......
  6. Jan 14, 2007 #5


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    "adiabatic heat exchanger" implies the heat is transferred from the hot fluid to the cold fluid. The change in energy of the hot fluid = change in energy of the cold fluid, or rather rate of energy transfer from the hot fluid = rate of energy transfer to the cold fluid.

    [tex]\dot{m_h}\,c_p_h\,\Delta{T_h}[/tex] = [tex]\dot{m_c}\,c_p_c\,\Delta{T_c}[/tex] where h and c are hot and cold, [tex]\dot{m}[/tex] is mass flow rate, cp is specific heat and [tex]\Delta{T}[/tex] is the change in temperature. Or instead of [tex]c_p\,\DeltaT[/tex], one could use the change in specific enthalphy directly, which one can find in a thermodynamic table as a funtion of temperature and pressure for the given fluid.
  7. Jan 16, 2007 #6
    Thats what i said...lol, but in laymen terms! :P
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