12/13/2023 0 Comments What does entropy mean![]() ![]() W T = h 3 – h 4s → W Ts = c p (T 3 – T 4s )įrom Ideal Gas Law we know, that the molar specific heat of a monatomic ideal gas is:Ĭ v = 3/2R = 12.5 J/mol K and C p = C v + R = 5/2R = 20.8 J/mol K The temperature (for isentropic process) of the gas at the exit of the turbine is T 4s = 839 K (566☌).Ĭalculate the work done by this turbine and calculate the real temperature at the exit of the turbine, when the isentropic turbine efficiency is η T = 0.91 (91%).įrom the first law of thermodynamics, the work done by turbine in an isentropic process can be calculated from: In this turbines the high-pressure stage receives gas (point 3 at the figure p 3 = 6.7 MPa T 3 = 1190 K (917☌)) from a heat exchanger and exhaust it to another heat exchanger, where the outlet pressure is p 4 = 2.78 MPa (point 4). An isentropic process can also be called a constant entropy process.Īssume an isentropic expansion of helium (3 → 4) in a gas turbine. See also: Thermal Efficiency of Brayton CycleĮxample: Isentropic Turbine Efficiency Isentropic process is a special case of adiabatic processes. thermal efficiency) such cycles (similarly for Rankine cycle) using enthalpies. The net heat rejected is given by Q re = H 4 – H 1Īs can be seen, we can describe and calculate (e.g. isobaric heat rejection – the residual heat must be rejected in order to close the cycle.The work done by turbine is given by W T = H 4 – H 3 isentropic expansion – the heated, pressurized air then expands on turbine, gives up its energy.The net heat added is given by Q add = H 3 – H 2 It is a constant-pressure process, since the chamber is open to flow in and out. isobaric heat addition – the compressed air then runs through a combustion chamber, where fuel is burned and air or another medium is heated (2 → 3).The work required for the compressor is given by W C = H 2 – H 1. ![]()
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