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posted by  MColeman on 11/4/2009 10:31:50 PM  |  status: Closed  |  Earned Karma: 50

Problem 52, Chapter 9

Course Textbook Chapter Problem Needs by
Thermodynamics Fundamentals of Thermodynamics (7th) by Sonntag, Borgnakke 9 52P 11/6/2009 at 4:00:00 PM
Question Details:
An insulated 2 m3 tank is to be charged with R-134a from the line flowing the refrigerant at 3MPa. The tank is initially evacuated, and the valve is closed when the pressure inside the tank reaches 3MPa. The line is supplied by an insulated compressor that takes in R-134a at 5oC, with a quality of 96.5%, and compressess it to 3MPa in a reversible process. Calculate the total work input to the compressor to charge the tank.
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posted by harry9(MNK) on 11/6/2009 3:05:37 AM  |  status: Live
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Response Details:

h1 = h2 + wc

 s1 = s2

inlet: T1 = 5oC, x1 = 0.965 use Table B.5.1 in textbook

s1 = sf + x1sfg = 1.0243 + 0.965×0.6995 = 1.6993 kJ/kg K,

h1 = hf + x1hfg = 206.8 + 0.965×194.6 = 394.6 kJ/kg

exit: P2 = 3 MPa

and  s2 = s1 = 1.6993 kJ/kg K;

T2 = 90oC, h2 = 436.2 kJ/kg

wc = h1 - h2 = -41.6 kJ/kg

Tank; VT = 2 m3, PT = 3 MPa

and Q = 0, W = 0, me = 0, m1 = 0, m2 = mi

u2 = hi = 436.2 kJ/kg

Final state: PT = 3 MPa, u2 = 436.2 kJ/kg

TT = 101.9oC, vT = 0.006783 m3/kg

mT = VT/vT = 294.84 kg

total work input to the compressor:

Wc = mT(wc)

Wc = 294.84*41.6

total work input to the compressor, Wc = 12 265 kJ

harry
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