THERMODYNAMICS - Lesson 18: Gas Power Cycles, Rankine

Описание

QUESTION 1
A gas turbine power plant operates on the simple Brayton cycle with air as the working fluid and delivers 32 MW of power. The minimum and maximum temperatures in the cycle are 310K and 900 K, and the pressure of air at the compressor exit is 8 times the value at the compressor inlet. Assuming an isentropic efficiency of 80 percent for the compressor and 86 percent for the turbine, determine the mass flow rate of air through the cycle. Account for the variation of specific heats with temperature.
(Answer: 794 kg/s)

QUESTION 2
A simple Rankine cycle uses water as the working fluid. The boiler operates at 6000 kPa and the condenser at 50 kPa. At the entrance to the turbine, the temperature is 450°C. The isentropic efficiency of the turbine is 94 percent, pressure and pump losses are negligible, and the water leaving the condenser is subcooled by 6.3°C. The boiler is sized for a mass flow rate of 20 kg/s.
(a) Determine the rate at which heat is added in the boiler.
(b) Determine the power required to operate the pump.
(c) Determine the net power produced by the cycle.
(d) Determine the thermal efficiency for the cycle.
(Answers: (a) 59,660 kW; (b) 122 kW; (c) 18,050 kW; (d) 0.3025)