1. Consider an ideal Stirling cycle using air as the working fluid. Air is at 400 K and 200 kPa at the beginning of the isothermal compression process, and heat is supplied to air from a source at 1800 K in the amount of 750 kJ/kg. Determine

(a) the maximum pressure in the cycle and

(b) the net work output per unit mass of air.

2. Consider a simple ideal Brayton cycle with air as the working fluid. The pressure ratio of the cycle is 6, and the minimum and maximum temperatures are 300 and 1300 K, respectively. Now the pressure ratio is doubled without changing the minimum and maximum temperatures in the cycle. Determine the change in

(a) the net work output per unit mass and

(b) the thermal efficiency of the cycle as a result of this modification. Assume variable specific heats for air.