A power plant operates on the air standard Brayton cycle with regeneration. Air enters the compressor at 14.5 psi and 537 R, and it leaves the compressor at 60 psia. The air exits the regenerator at 1120 R, and it exits the combustion chamber at 1700 R. The compressor and turbine each have an isentropic efficiency of 0.85. The mass flow of the air is 17.8 lbm/s. a. Sketch the corresponding T-s diagram.
b. Calculate the thermal efficiency of the cycle.
c. Calculate back work ratio.
d. Calculate the regenerator effectiveness.
e. Calculate the mass flow rate of the air, in lb/s.

To save energy, the air supply to a 2000 ft office has been shut off overnight and the room temperature has dropped to 40°f. in the morning, the thermostat is reset to 70°f and warm air at 120 f begins to flov in at 200ft'/min. the air is well mixed within the room, and an equal mass flow of air at room temperature (changing with time) is withdrawn through a return duct. the air pressure is nearly 1 atm everywhere. ignoring heat transfer with the surroundings and kinetic and potential energy effects, estimate how long it takes for the room temperature to reach 70°f. plot the room temperature as a function of time.