Air enters the compressor of a Brayton cycle at 250 K and 0.1 MPa. The pressure ratio is 4 to 1 and the maximum cycle temperature is 1300 K. The compressor and turbine efficiencies are 0.85. Using data from Appendix C.2 to account for variable specific heats, determine

(a) The net specific work (kJ/kg)

(b) The thermal efficiency

(c) The ratio of compressor to turbine work.

Appendix C.2

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TKK) 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400 410 420 430 440 h (kJ/kg) 325.42 335.49 345.55 355.62 365.68 375.73 385.79 395.85 405.91 415.97 426.04 436.11 446.18 456.26 466.34 476.43 486.53 496.64 506.75 516.88 527.02 537.17 547.33 557.51 567.70 u (kJ/kg) 268.14 275.32 282.49 289.67 296.85 304.02 311.20 318.38 325.56 332.74 339.93 347.12 354.31 361.51 368.72 375.94 383.16 390.39 397.63 404.89 412.15 419.42 426.71 434.01 441.33 s (kJ/kg-K) 3.4764 3.5255 3.5723 3.6171 3.6599 3.7009 3.7404 3.7783 3.8149 3.8502 3.8844 3.9174 3.9494 3.9804 4.0105 4.0397 4.0682 4.0959 4.1228 4.1491 4.1748 4.1999 4.2244 4.2483 4.2717 C₂ (ki/kg-K) 1.007 1.007 1.006 1.006 1.006 1.006 1.006 1.006 1.006 1.006 1.007 1.007 1.008 1.008 1.009 1.009 1.010 1.011 1.012 1.013 1.014 1.016 1.017 1.018 1.020 C₂ (ki/kg-1) 0.716 0.716 0.716 0.716 0.716 0.717 0.717 0.717 0.717 0.718 0.718 0.719 0.719 0.720 0.721 0.721 0.722 0.723 0.724 0.725 0.727 0.728 0.729 0.731 0.732 y (=Cp/Cv) 1406 1.405 1.405 1.404 1.404 1.404 1.403 1.403 1.403 1.402 1.402 1.401 1.401 1.400 1.400 1.399 1.399 1.398 1.398 1.397 1.396 1.395 1.395 1.394 1.393