Heat Rate
The heat rate is defined as the total amount of energy required to produce one kilowatt-hour (kWh) of electricity by an electric generator or power plant.
It is the input rate required for generating unit power. The heat rate can also be described as the ratio of thermal inputs to electrical output. The lower the heat rate higher the efficiency. In thermal generating system, incoming and outgoing energy typically exist in the same value or unit. The heat amount is proportional to the input of chemical energy divided by the liberated electrical energy.
The formula of heat rate is
Rh = Ws × c × ΔT
Where,
Rh is heat rate in btu/hr,
Ws is steam flow in lb/hr,
c = specific heat capacity in btu/lb ∘F,
ΔT is the temperature difference in ∘F.
Solved Example
Example 1: Calculate the heat rate if steam enters a turbine at 400oF at atmospheric pressure and leaves the turbine at 200oF. Steam at 500 lb flows through the turbine each hour during normal operation.
Solution:
Given parameters are,
Ws = 500 lbs/hr
c = 0.48
Tin = 400oF
Tout = 200oF
ΔT = 400 – 200
ΔT = 200oF
We have the Formula,
Rh = Ws × c ×ΔT
Rh = 500 × 0.48 × 200
Therefore, Rh = 48000 btu/hr
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