Max BFW (Boiler Feed Water)Temp. at 800 psi
Max BFW (Boiler Feed Water)Temp. at 800 psi
(OP)
I am trying to heat the BFW at 800 psi, what is the maximum temperature BFW (water) can be at (liquid state, without any vapor)? What method was used to calculate Max temp. of water?





RE: Max BFW (Boiler Feed Water)Temp. at 800 psi
RE: Max BFW (Boiler Feed Water)Temp. at 800 psi
The maximum PRACTICAL temperature of the BFW should be less than the boiling temperature (known as the saturation temperature) of the water at a given pressure.
This "subcooling" of the liquid state will ensure against cavitation as the flow generates local low pressure spots at elbows, flange pairs, or other irregularities in the piping.
My guess is to design for at least 10 - 20 Fahrenheit degrees below saturation of the liquid, but some piping/process/boiler people should weigh in on this one.
RE: Max BFW (Boiler Feed Water)Temp. at 800 psi
The best way to avoid insufficent NPSH is to ensure the liquid is subcooled below the boiling temperature, and a subcooling of 20 F is equivalent to allowing 130 psi pressure drop from the heat exchanger to the pump inlet nozzle.
The bigger issue is whether there are system upsets which will cause the pressure to drop below the 800 psi design presure ( ie, load changes or filter pluggage). If so, it is essential that the fluid heating system respond quicker than fast, because it only takes 30 seconds of inadequate NPSH to wreck a pump.
RE: Max BFW (Boiler Feed Water)Temp. at 800 psi
It is worth noting in this discussion that it is typical of multi-heater turbine-generator installations for the "top" feedwater heaters to be after the feedwater pump and (of course) before the boiler.
No doubt this is related to the potential problems of pump burn-out due to cavitation.
"newengr" should note that this discussion illustrates the differences between (theoretical) optimal first-order design and the very important (seemingly secondary) considerations of safety, reliability, operating margin for transients, life-cycle costs,...
RE: Max BFW (Boiler Feed Water)Temp. at 800 psi
(savings in $)? Also, any savings in raising pressure in deaerators from 3 psi to 15 psi? Shouldn't use as much oxygen scavenger? What is benefit, how do you calculate the savings ($)?
RE: Max BFW (Boiler Feed Water)Temp. at 800 psi
Delta power = w*(h*-ho), whre ho is the used energy endpoint of steam leaving the turbine to the condenser
RE: Max BFW (Boiler Feed Water)Temp. at 800 psi
Download wasp from www.chempute.com/wasp.htm