# MERM Error?



## navyasw02 (Oct 1, 2010)

I was trying to work a 6MS MD #78 and I think I found an error in the MERM regarding the NTU Method equations. I think eq 36.81 and 36.82 are reversed, meaning that 36.81 where it says Cmin = Ccold should be for Cmin = Chot. Same goes for 36.82, Cmin = Ccold. Otherwise, the C terms would cancel in the equations.

Can anybody else verify that? I just want to make sure I'm not messing something up.


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## Sschell (Oct 1, 2010)

which edition do you have? mine (12th edition) appears to be correct:

36.81 (Cmin=Ccold):

[Chot(Thot,in-Thot,out)]/[Cmin (Thot,in-Tcold,in)]


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## navyasw02 (Oct 1, 2010)

sschell_PE said:


> which edition do you have? mine (12th edition) appears to be correct:
> 36.81 (Cmin=Ccold):
> 
> [Chot(Thot,in-Thot,out)]/[Cmin (Thot,in-Tcold,in)]


Weird, I have the 12th edition also and mine's reversed. My 36.81 is:

Cmin = Ccold

E = Ccold(Tcold out - Tcold in) / Cmin(Thot,in - Tcold, in). If Cmin = Ccold, it would just simplify to (Tcoldout-Tcoldin)/(Thotin-Tcoldin) which is not correct.

Your version is correct. That's really odd that the same edition can have different eqns.


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## Sschell (Oct 1, 2010)

Quick somebody call Lindeburg!


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## navyasw02 (Oct 1, 2010)

sschell_PE said:


> Quick somebody call Lindeburg!


Oh I did. I already informed the state board as well.


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## Relvinim (Oct 1, 2010)

navyasw02 said:


> sschell_PE said:
> 
> 
> > which edition do you have? mine (12th edition) appears to be correct:
> ...


My edition (12th) has the same error as yours. Thanks for bringing this up because i thought I was losing my mind.


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