An open-cycle gas turbine plant is used to generate power in an oil refinery. The gas turbine unit drives a generator which supplies electric motors of 2400 kW; the overall mechanica! and electrical...

Subject: thermodynamics


Extracted text: An open-cycle gas turbine plant is used to generate power in an oil refinery. The gas turbine unit drives a generator which supplies electric motors of 2400 kW; the overall mechanica! and electrical efficiency is 92%. Some of the exhaust gas from the turbine at 530°C is supplied to a furnace in the refinery at a rate of 2 kg/s; the remainder of the exhaust gas is passed in counter-flow through a heat exchanger where it heats the air leaving the compressor, and then passes to exhaust at 400 °C. The compressor has a pressure ratio of 8 and the air at entry is at 1.013 bar and 20°C. The pressure loss in the air side of the heat exchanger is 0.16 bar, the pressure loss in the combustion chamber is 0.12 bar, and the pressure loss in the gas side of the heat exchanger is 0.05 bar. The isentropic efficiencies of the compressor and turbine are 0.85 and 0.92 respectively. Neglecting heat losses in the heat exchanger, and the mass flow rate of fuel, calculate: (i) the mass flow rate of air entering the compressor; (ii) the temperature of the air entering the combustion chamber; (iii) the overall cycle efficiency. (10.82 kg/s; 421.0°C; 34.2%)