how much steam lbs/hr will a dryer take

[Janus123]

Hello,

I need help resolving the heat balance equations for dryer. My process requires 500 CFM of at 200 Deg F. Ambient air at 75 deg F is being heated in a steam coil injected with 60 PSIG sat steam. Saturated condensate is returned at 252 Deg F. I need to calculate the amount of steam the dryer needs. My calculations yield approx 71.4 8Lbs/hr of stem but I feel I am missing something - intuitively should be a bit more.
Any help would be greatly appreciated with equation and yield.
My calculation was:

cfmx1.08xDelta T/Hfg at = 500x1.08x125/943 (Latent heat at 252 DEg F)

Thanks and regards
Janus

 

[dvd]

How many pounds of air per hour is 500 cfm at 200F?

 

[Janus123]

thanks
without accurate pressure dont know but approx I would get 37.5 lbs/min or
2,250 lbs per hour.

 

[FredRosse]

"My process requires 500 CFM of at 200 Deg F"
That is 1808 pounds per hour of air. Temp rise is 75F to 200F = 125F x 0.24 BTU/LBm-F = 54250 BTU/hr heat flow

"steam coil injected with 60 PSIG sat steam"
That steam pressure corresponds to a saturation temperature of 307F, and the latent heat of condensation is 904 BTU/LBm.

"Saturated condensate is returned at 252 Deg F" conflicts with the given steam saturation temperature corresponding to 60 PSIG, perhaps the condensate outlet is subcooled? If it is subcooled at 252F, then additional energy (55 BTU/LBm)is taken from the steam, 960 BTU/LBm total.

Calculating the steam mass flow required, (54250 BTU/hr) / (930 BTU/LBM) = 56.5 PPH Steam Required.

If you didn't really intend "500 CFM of at 200 Deg F", but actually need 500 SCFM, then the air mass flow is 2295 PPH, and the heating steam requirement is 27% higher, or 71.7 PPH steam.

 

[dvd]

There is no substitute for checking that the units really did cancel.