Project ForgeIn a simple Brayton cycle, the pressure ratio is 8 and temperatures at the entrance of compressor and turbine are 300 K and 1400 K, respectively. Both compressor and gas turbine have isentropic efficiencies equal to 0.8. For the gas, assume a constant value of cp (specific heat at constant pressure) equal to 1 kJ/kgK and ratio of specific heats as 1.4. Neglect changes in kinetic and potential energies. The power required by the compressor in kW/kg of gas flow rate is
- A194.7
- B243.4
- 304.3
- D378.5
Explanation
Ideal compressor exit temperature: T2s = T1·rp^((γ−1)/γ) = 300×8^(0.2857) = 300×1.8114 = 543.4 K. Actual compressor work (with isentropic efficiency in the denominator, since actual work exceeds ideal for a compressor): Wc = cp(T2s−T1)/ηc = 1×(543.4−300)/0.8 = 243.4/0.8 = 304.3 kJ/kg.
Source: GATE ME 2013 (Booklet Code A) (2013)
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