Page 23 - Advanced Gas Turbine Cycles

xx Notation
(continued)
Symbol Meaning Typical Units
’ (e.g. a’, b’, 1’. states in feed heating train, in reheating or intercooling
2’, 3’. 4’)
-(e.g. T) mean or averaged (e.g. temperature)
Note on eificiencies
7 is used for thermal efficiency of a closed cycle, but sometimes with a subscript
(e.g. 1)~ for thermal efficiency of a higher cycle); % is used for (arbitrary) overall efficiency
of a plant.
A list of efficiencies is given below.
Plant Them1 Efficiencies 7
m higher cycle
rh lower cycle
WP combined cycle
llco cogeneration plant
WAR Carnot cycle
Plant (Arbitrary) Overall Efficiencies l)o
(%)H higher plant
(%kP combined plant
(%)L lower plant
Rational Efficiencies
Component Efficiencies
r)B boiler
W compressor, isentropic
m turbine, isentropic
% polytropic

Cycle Descriptions

The nomenclature originally introduced by Hawthorne and Davis is followed, in which
compressor, heater, turbine and heat exchanger are denoted by C, H, T and X respectively
and subscripts R and I indicate reversible and irreversible. For the open cycle the heater is
replaced by a burner, B. In addition subscripts U and C refer to uncooled and cooled
turbines in a cycle and subscripts 1, 2, . . . indicate the number of cooling steps. Thus, for
example [CBTXIIc2 indicates an open irreversible regenerative cycle with two steps of
turbine cooling.