A Brayton gas turbine typically operates with only a small amount of fuel added so that the inlet temperatures of the turbine are kept relatively low because of material degradation at higher temperatures, thus the flowing streams can be modeled as only air. Refer to the online supplement for stream labels. Consider a Brayton cycle modeled with air under the following conditions: TA = 298 K, PA = PD = 0.1 MPa, PB = 0.6 MPa, and TC = 973 K. The efficiencies of the turbine and compressor are to be 85%. Consider air as an ideal gas stream with CP = 0.79·CP,N2 = 0.21·CP,O2. Determine the thermal efficiency, heat required, and net work output per mole of air assuming
(a) The heat capacities are temperature-independent at the values at 298 K.
(b) The heat capacities are given by the polynomials in Appendix E.
