# MERM Questions Doubts Discisson Etc



## audacious (Jan 8, 2011)

I was going trhough this problem but got stuck when the solution says Evaluate hfg~ 1060 btu/ lbm

Can anyone here explain how this value is calculated?

Thanks


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## MadDawg (Jan 8, 2011)

audacious said:


> I was going trhough this problem but got stuck when the solution says Evaluate hfg~ 1060 btu/ lbmCan anyone here explain how this value is calculated?
> 
> Thanks



My MERM is at work...what does the question say?


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## Clydeman (Jan 10, 2011)

In MERMS take a look at equation 38.19 which calculates the enthalpy of the moisture in air. The equation is:

hw = cp,water vapor x T = hfg

hw approx equal to (0.44 Btu/lbm F)xT(in deg F) + 1061 BTU/lbm

This approximation is for low pressure superheated vapor at room temperature. If you look in the steam tables this hfg value corresponds to 58F.


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