A gas-turbine plant operates on the regenerative Brayton cycle, the schematic diagram of which is shown in Fig. Q 1, with two stages of reheating and two-stages of intercooling between the pressure limits of 100 and1200 kPa . The working fluid is air. The air enters the first and the second stages of the compressor at 300 K and 350 K , respectively, and the first and the second stages of the turbine at 1400 K and 1300 K , respectively. Assuming both the compressor and the turbine have an isentropic efficiency of 80%. The regenerator has an effectiveness of εregen=75% . Assume variable specific heats (i.e., use the concept of relative pressures) and the intermediate pressures of intercooling and reheating is the square root of the product of inlet and exit pressures for intercooling and reheating. Make other the necessary assumptions and determine (a) the back work ratio, β , and the net work output, , wnet (b) the thermal efficiency (that is the first-law efficiency, ηi ) and (c) the relative efficiency (that is the second-law efficiency, ηii ). Draw the correct T-s diagram for this cycle with labelled property values. Rair= 287 J/(kg K).
Q#1. A gas-turbine plant operates on the regenerative Brayton cycle, the schematic diagram of which
is shown in Fig. Q 1, with two stages of reheating and two-stages of intercooling between the pressure limits of
100 and1200 kPa . The working fluid is air. The air enters the first and the second stages of the compressor at 300 K and 350 K , respectively, and the first and the second stages of the turbine at 1400 K and 1300 K , respectively. Assuming both the compressor and the turbine have an isentropic efficiency of 80%. The regenerator has an effectiveness of
εregen=75% . Assume variable specific heats (i.e., use the concept of relative pressures) and the intermediate pressures
of intercooling and reheating is the square root of the product of inlet and exit pressures for intercooling and reheating. Make other the necessary assumptions and determine
(a) the back work ratio,
β , and the net work output,
, wnet
(b) the thermal efficiency (that is the first-law efficiency,
ηi ) and
(c) the relative efficiency (that is the second-law efficiency,
ηii ).
Draw the correct T-s diagram for this cycle with labelled property values. Rair= 287 J/(kg K).
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