23. Air flows through a frictionless duct with a constant cross-sectional area. At the inlet of the duct, the temperature, pressure and Mach number are 252K,184kPa and 1.64 , respectively. If heat is transferred at the rate of 50kJ/kg, determine the a) stagnation temperature and Mach number at the exit of the duct, b) entropy change and c) change in the stagnation pressure. (Ans. a) 473.6K,1.15; b) 172.7kJ/kgK; c) 130.7kPa