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Unformatted text preview: to account the variation of specific heats with temperature, determine (a) the pressure and temperature at the end of the heat‐addition process, (b) the net work output, (c) the thermal efficiency, and (d) the mean effective pressure for the cycle. Approximate answers: (a) 4000 kPa, 1500 K: (b) 400 kJ/kg; (c) 50 percent; (d) 500 kPa. Solution The process is sketched below on a P‐v diagram. P 3 wout qin 4 2 qout win 1 TDC BDC v a) Consider the isentropic expansion from 1 to 2. We use (7‐50) in the text to account for variable specific heats. Then v 2 1 1 vr2 . (1) v 1 r 8 v r1 From Table A‐17 at 300 K, vr1 = 621.2 and u1 = 214.07 kJ/kg. Then from (1) vr2 = 77.75. Interpolating in Table A‐17 with vr2 gives T2 = 673.1 K and u2 = 491.22 kJ/kg. The ideal gas law gives (see Problem 1 for ideal gas calculation) P2 = 1705 kPa. For the constant volume heat addition process, qin + u2 ‐ u3 = 0 or u3 = qin + u2 = 1241.22 kJ/kg. Knowing...
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This homework help was uploaded on 03/02/2014 for the course CHEM 1010 taught by Professor Staff during the Spring '08 term at Utah State University.

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