Clean Steam Generation

[tedlove]

I have a Steam Heat Exchanger rated for 5,157 lbs/hr of 85psi Primary Steam and this can produce 4,000 lbs/hr of clean steam at 50psi.

The equipment is rated for 150psi. I want to find out how much steam can we produce at 110psi Clean Steam with a input Primary Steam pressure of 140psi.

The given area of the primary steam tube in the generator is 2sqft the stainless steel tube OD is 3/4 inch.

The vendor of this generator is stating that at 140psi primary steam and a clean steam pressure of 110 that we can produce 800 lbs/hr of the clean steam. I don't understand where they are getting these calculations.

The available heat transfer of the steam is about 900Btu/lb so we can calculate the Btu transfered per hour 3.6Mbtu/hr.
Any help would be appreciated.

 

[TBP]

LMTD is a big factor in sizing heat exchangers. I'll bet that's the reason for the reduced output.

 

[tedlove]

TBP - what do you suggest for LMTD. I calculated 68.6F which is not exactly reasonable since the steam at 324F will not go all the way down to 212, I know it should be above that, but that is what I based my LMTD on (324-297) - ( 212-70) Most the the energy is not in the temp change, but in the phase changes.

 

[tedlove]

I guess I should add the temperature of the DI water feed to the steam generator, 70F

 

[TBP]

You'll need to heat the cold side up past 212*F. It'll need to be saturation temp at 110 PSIG. The limiting factor could be nozzle connection sizes. Have you got enough pump head to push the feedwater into this rig at the higher operating pressure?