Feedwater heaters

1. MEWAR
UNIVERSITY
TOPIC :- FEEDWATER HEATER

2. FEEDWATER HEATER
 A feedwater heater is a power plant component used to
pre-heat water delivered to a steam generating boiler.
 In a steam power plant, feedwater heaters allow the
feedwater to be brought up to the saturation temperature
very gradually.
 It improves the thermodynamic efficiency of the system
by reducing plant operating costs and also helps to avoid
thermal shock to the boiler metal.

4. CYCLE EXPLANATION
 The energy used to heat the feedwater is usually derived from
steam extracted between the stages of the steam turbine. Therefore,
the steam that would be used to perform expansion work in the
turbine (and therefore generate power) is not utilized for that
purpose.
 The percentage of the total cycle steam mass flow used for the
feedwater heater is termed the extraction fraction and must be
carefully optimized for maximum power plant thermal efficiency
since increasing this fraction causes a decrease in turbine power
output.

5. TYPES OF FEEDWATER HEATERS
FWH
OPEN FWH CLOSED FWH

6. OPEN FEEDWATER HEATERS
An open heat exchanger is one in which extracted steam is
allowed to mix with the feedwater. This kind of heater will
normally require a feed pump at both the feed inlet and
outlet since the pressure in the heater is between the boiler
pressure and the condenser pressure.
A deaerator is a special case of the open feedwater heater
which is specifically designed to remove non-condensable
gases from the feedwater.

8. CLOSED FEEDWATER HEATERS
 Closed feedwater heaters are typically shell and tube heat
exchangers where the feedwater passes throughout the tubes and is
heated by turbine extraction steam. These do not require separate
pumps before and after the heater to boost the feedwater to the
pressure of the extracted steam as with an open heater.
 Many power plants incorporate a number of feedwater heaters and
may use both open and closed components. Feedwater heaters are
used in both fossil- and nuclear-fueled power plants.

10. ECONOMIZER VS FEEDWATER HEATERS
 An economizer serves a similar purpose to a feedwater heater, but is technically
different as it does not use cycle steam for heating. The economizer uses the
lowest-temperature flue gas from the furnace to heat the water before it enters the
boiler.
 Most nuclear power plants do not have an economizer. However, the
Combustion Engineering System 80+ nuclear plant design and its evolutionary
successors, (e.g. Korea Electric Power Corporation's APR-1400) incorporate an
integral feedwater economizer. This economizer preheats the steam generator
feedwater at the steam generator inlet using the lowest-temperature primary
coolant.

11. ANY