Heat Exchanger Steam flow rate versus pressure

[BronYrAur]

I know there is an simple answer to this ... at least I think so.

I have a sterilizer that can accept a steam pressure range of 30 psig to 80 psig. The required flow rate at 30 psig is 200 Lbs/hr, and the flow at 80 psig is 300 lbs/hr. Seems like it should be the other way around.

What am I missing?

 

[ione]

Well, specific enthalpy of evaporation (latent heat), which generally is the exploitable part in the heat exchange process, decreases as pressure increases.
In your specific case, at 30 psig the specific enthalpy of evaporation is approx 929 Btu/lb, while at 80 psig it is approx 892 Btu/lb. Anyway the flow rate required should only increase by a 4% and not by 50%, so your figures are quite odd.

 

[25362]

How is the steam flow rate measured? Is the sterilizer at atmospheric pressure?

 

[BronYrAur]

Don't know. The info I listed is from the manufacturer's spec sheet.

 

[25362]

The manufacturer is probably telling that, if needed, the pressure and the heat duty could be increased.

 

[MortenA]

The higer the steam pressur ethe higher the dT - maybe the high P is for high cold side flow rates or maybe a higher exit temperature?