Understanding the Function and Placement of Drain Coolers in Feed Water Heaters

[ashoksmulpuri]

What is the function of drain cooler in a feed water heater and is there any reason that it is integral within the heat exchanger but some times it is also placed outside the heater.

 

[russ_watters]

The only context I've heard of a "drain cooler" is for cooling water that is to be discharged to a drain below 140F in accordance with OSHA regulations.

 

[ank_gl]

What is the function of drain cooler in a feed water heater and is there any reason that it is integral within the heat exchanger but some times it is also placed outside the heater.

In a steam power plant, term drain cooler refers to the drain cooler section of the closed feed water heater. A closed feed water is a heat exchanger where steam bled from the turbine transfers heat to the feed water in a non contact heat exchanger(eg shell & tube type). Steam, as it cools, is first desuperheated(if in superheated stage) in the first section which is called the desuperheater, condensed in the condenser section, & then cooled in the drain cooler part.

The three sections do not make different components, its just one component with different physical phenomenons occurring in different section. The last part where the liquid cools is termed the drain cooler.

 

[ashoksmulpuri]

thanks for ur reply.

is there any specific reason that drain cooler is placed outside the closed fed water heater?

 

[ank_gl]

I actually haven't seen it being placed outside

But i would reason, if it is placed outside the shell, since that it is already condensed(counterflow heat exchanger), it is used to heat feedwater at its inlet. Maybe that's why:shy:

 

[Canes2552]

I have seen a drain cooler placed outside the FWH. the FWH transferred heat from the the steam bled from the high pressure turbine I believe to the feed water. The drain cooler exchanged heat from the condensed steam from the FWH (usually a steam and water mixture) to bearing cooling water.

the effect achieved I suppose is to have the steam heat the feed water and then have a separate water system cool the steam/water mixture to be discharged to the condenser sump.

I also believe that it would be easier to clean or preform maintenance on the drain cooler if it is separated from the feed water heater. Especially if you are using bearing coolant water which is more susceptible to fouling and requires cleaning more often.