Calculation of thermal efficiency of a three-circuit steam and gas plant Author: Valery Ochkov ([email protected]), Aung Thu Ya Tun ([email protected]), Moscow Power Engineering Institute (MPEI) Start > > > > Steam turbine cycle Input data: > > > > > > > > > > > > > > Functions and procedures The specific enthalpy of the steam entering the turbine HPP: > (2.1) The specific enthalpy of steam at outlet of the turbine HPP: > (2.2) Specific work of HPP steam turbine: > (2.3) The temperature of the steam at the outlet of the HPP turbine: > (2.4) The specific enthalpy of steam at the point 10: > (2.5) > (2.6) The balance of the mixing streams at points 9 and 10: > (2.7) The temperature of steam at the inlet to the MPP of the turbine: > (2.8) > (2.8) > (2.9) > Specific enthalpy of water vapor at the inlet to the MPP of the turbine: > (2.10) Specific enthalpy of steam at the outlet of the turbine MPP: > (2.11) C : > (2.12) The temperature of the steam at the outlet of the MPP of the turbine: > (2.13) The specific enthalpy of steam at point 13: > (2.14) > (2.15) Balance when mixing streams at points 12 and 13: > (2.16) The temperature of steam at the inlet to the LPP of the turbine: > (2.17) > (2.18) The specific enthalpy of steam at outlet of the turbine LPP: > (2.19) Specific LPP operation of a steam turbine: > (2.8) > (2.20) The degree of dryness of the steam at the outlet of the turbine LPP: > (2.21) Condensate temperature: > (2.22) Specific enthalpy of condensate: > (2.23) The specific enthalpy of the feed water high pressure circuit (internal relative pump efficiency of 75%): > (2.24) > (2.25) > (2.26) > (2.27) The specific operation of the pump high-pressure circuit > (2.28) Specific enthalpy of feed water of medium pressure circuit (internal relative efficiency of the pump is equal to 75%): > (2.29) > (2.30) The specific operation of the pump high-pressure circuit: > (2.31) Specific enthalpy of feed water of the low pressure circuit (internal relative efficiency of the pump is equal to 73%): > (2.8) > (2.20) > (2.32) > (2.33) > (2.34) Specific work of the low pressure circuit pump: > (2.35) Thermal efficiency of the STP cycle: > (2.36) Gas turbine cycle Input data: > > > > > > Specific enthalpy of fresh air > (3.1) Specific entropy of fresh air > (3.2) Specific entropy air at the outlet of the compressor: > Air temperature at the outlet of the compressor: > (3.3) The specific enthalpy of the air at the outlet of the compressor: > (3.4) > (2.8) > (2.20) > (2.32) (3.4) Gas pressure at the inlet to the GT: > Specific entropy of gas at the entrance to the GT: > (3.5) Specific enthalpy of gas at the inlet to the GT: > (3.6) Gas pressure at the outlet from the gas turbine unit: > Specific entropy of gas at the outlet of GTP: > Gas temperature at the outlet of the GTP: > (3.7) Specific enthalpy of gas at the outlet of GTP: > (3.8) Heat supplied in the combustion chamber: > (3.9) The specific operation of the gas turbine: > (3.10) The specific operation of the compressor: > (3.11) Thermal efficiency of the GTP cycle: > (3.12) Combined (binary) cycle > (2.8) > (2.20) > (2.32) (3.4) Specific enthalpy of gas at the outlet of the recovery boiler: > Ratio of gas and steam mass flow of a high-pressure > (4.1) Ratio of gas and steam mass flow of a medium-pressure > (4.2) Ratio of gas and steam mass flow of a low-pressure > (4.3) Ratio of gas and steam mass flow > (4.4) Specific heat supplied to the combustion chamber: > (4.5) Specific work of the gas turbine cycle > (4.6) Specific work of the steam turbine cycle > (4.7) Hence the thermal efficiency of the combined (binary) cycle is higher than separate steam or gas turbine cycles: > (4.8).