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  • Lliño
    Lliño

    Member • Oct 10, 2009

    Carnot Engine Problem

    QUESTION
    A Carnot Engine operating between 900 Fahrenheit and 90 Fahrenheit produces 40,000 ft-lb of work. Determine (a) the heat supplied, (b) the change in entropy during heat rejection and (c) the thermal efficiency of engine. (answers should be in BTU)

    MY ATTEMPT
    (a) 22.74 BTU
    (c) 60%

    Am i leading to correct answers
    Replies
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Replies

  • yadavundertaker mohit

    Member • Oct 10, 2009

    Lindell
    QUESTION
    A Carnot Engine operating between 900 Fahrenheit and 90 Fahrenheit produces 40,000 ft-lb of work. Determine (a) the heat supplied, (b) the change in entropy during heat rejection and (c) the thermal efficiency of engine. (answers should be in BTU)

    MY ATTEMPT
    (a) 22.74 BTU
    (c) 60%

    Am i leading to correct answers

    I don't know in BTU but i atleast can try it


    T1=900 F
    T2=90F
    W=40,000 ft-lb

    n=(T1-T2)/T1

    (900-90)/900

    =98.88%
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  • antenna

    Member • Oct 10, 2009

    Yadavundertaker, youhave use that formula(1-t1/t2) with t in kelvin.
    Use that,you would get the right ans.Any way the efficiency of a heat engine can reach 60% to 65% at max.
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  • Lliño Del Rosario

    Member • Oct 11, 2009

    1 ft-lb = 9.478* 10^-4 BTU

    (a) 22.74 BTU
    W=N QH
    =.60(40000 ft-lb * (9.478* 10^-4 BTU / 1 ft-lb)
    = 22.74 BTU

    am i correct?
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  • raj87verma88

    Member • Oct 11, 2009

    T1 = 755.222 K
    T2 = 305.222 K

    1) Heat Supplied Qc = nRT1 ln(Vb/Va)
    ab is the initial Isothermal path.
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