Calculation of thermal efficiency of combined- cycle plant

Author: Valery Ochkov ([email protected]), Aung Thu Ya Tun ([email protected]), Moscow Power Engineering Institute (MPEI)

Start > > > > Steam turbine cycle Input data: > (2.1) > (2.2) > (2.3) Specific entropy of live steam (the turbine inlet): > Specific enthalpy of live steam (the turbine inlet): > Outlet steam specific entropy from the turbine (an ideal process of the steam extension) > Dryness of steam in outlet of the turbine: >

(2.4) Outlet wet steam temperature from the turbine > (2.5) Outlet wet steam specific enthalpy from of the turbine: >

(2.6)

Specific work of steam in the turbine: >

(2.7)

Specific enthalpy of water at saturated line at temperature in the condenser >

(2.8)

Specific entropy of water at saturated line at temperature in the condenser >

(2.9)

Specific enthalpy of condensate > Pressure of feed water > Specific entropy of feed water (an ideal process in the pump): > Temperature of feed water: > (2.10) Specific enthalpy of feed water: >

(2.11) >

Specific useful work of the feed pump: >

(2.12)

Specific heat supplied to the boiler: >

(2.13)

Hence the thermal efficiency of the steam turbine cycle:

>

(2.14) Gas turbine cycle Input data: > > > > > Specific enthalpy of air entering the compressor: >

(3.1)

Specific entropy of air entering the compressor: >

(3.2)

Specific entropy of air at compressor outlet: > The air temperature at the outlet of the compressor: > (3.3) Specific enthalpy of air at compressor outlet: >

(3.4)

Inlet gas pressure, specific entropy and specific enthalpy to the gas turbine > Specific entropy of gas at the entrance to GTP: >

>

(3.5)

Specific enthalpy of gas at the entrance to GTP: >

(3.6)

The gas pressure at the exit of the gas turbine: > Specific entropy of gas at the exit of the gas turbine: > The gas temperature at the exit of the gas turbine: > (3.7) Specific enthalpy of gas leaving the gas turbine: >

(3.8)

Specific heat supplied to the combustion chamber: >

(3.9)

Specific work of the gas turbine >

(3.10)

Specific work of the air compressor >

(3.11)

Thermal efficiency of cycle gas turbine:

>

(3.12)

Combined (binary) cycle Outlet gas pressure and specific enthalpy from the steam boiler > Specific enthalpy of gas at the outlet of the recovery boiler: >

(4.1) >

>

(3.5)

(4.1)

Ratio of gas and steam mass flow

>

(4.2) Specific heat supplied to the combustion chamber: >

(4.3)

Specific work of the gas turbine cycle >

(4.4)

Specific work of the steam turbine cycle >

(4.5)

Hence the thermal efficiency of the combined (binary) cycle is higher than separate steam or gas turbine cycles:

>

(4.6)