MILHDBK1003/7
5.1.7.2
Turbine Heat Rates
a) Gross Turbine Heat Rate. The gross heat rate is determined by dividing
the heat added in the boiler between feedwater inlet and steam outlet by the kilowatt
output of the generator at the generator terminals. The gross heat rate is expressed in
Btu per kWh. For reheat cycles, the heat rate is expressed in Btu per kWh. For reheat
cycles, the heat added in the boiler includes the heat added to the steam through the
reheater. For typical values of gross heat rate, see Table 7.
Table 7
Typical Gross Turbine Heat Rates
+)))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))),
*
*
Throttle Throttle Reheat
Cond.
* Turbine Generator Pressure Temp.
*
Temp.
Pressure
HeatRate
*
* Rating, kW
psig
F
F
in. Hg Abs. Btu/kWh
*
*
* 11,500
*
600
825

1 1/2
10,423
*
* 30,000
850
900

1 1/2
9,462
* 60,000
*
1,250
950

1 1/2
8,956
* 75,000
*
1,450
1,000
1,000
1 1/2
8,334
*
*125,000
1,800
1,000
1,000
1 1/2
7,904
.))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))
b) Net Turbine Heat Rate. The net heat rate is determined the same as for
gross heat rate, except that the boiler feed pump power input is subtracted from the
generator power output before dividing into the heat added in the boiler.
c) Turbine Heat Rate Application. The turbine heat rate for a
regenerative turbine is defined as the heat consumption of the turbine in terms of "heat
energy in steam" supplied by the steam generator, minus the "heat in the feedwater" as
warmed by turbine extraction, divided by the electrical output at the generator
terminals. This definition includes mechanical and electrical losses of the generator
and turbine auxiliary systems, but excludes boiler inefficiencies and pumping losses and
loads. The turbine heat rate is useful for performing engineering and economic
comparisons of various turbine designs.
Plant Heat Rates. Plant heat rates include inefficiencies and losses external
5.1.7.3
to the turbine generator, principally the inefficiencies of the steam generator and
piping systems; cycle auxiliary losses inherent in power required for pumps and fans;
and related energy uses such as for soot blowing, air compression, and similar services.
a) Gross Plant Heat Rate. This heat rate (Btu/kWh) is determined by
dividing the total heat energy (Btu/hour) in fuel added to the boiler by the kilowatt
output of the generator.
54