Heat Exchanger Retrofit 2

[khanlon]

I'm currently investigating the replacement of a steam boiler with localized hot water systems to supply heat to mixing vessels.
I can find the heat transfer coefficient of the current steam set-up but need to determine what would occur if water instead of steam was used as the heating medium. Specifications on the actual mixers is fairly limited.
I was going to use;
Q=m(h1-h2)for steam and equate it to water i.e. Q=m(h1-h2)(for current steam)=mCp(LMTD) (for proposed hot water system)however this leaves me with two unknowns m and LMTD.
Any advise on such matters would be greatly appreciated.

 

[TBP]

I'm curious - what's the perceived advantage going from steam to hot water?

 

[panduru]

Yes, even I was wondering about the same.

 

[Latexman]

khanlon,

First, you have not given us much to work with. A useful response depends on the overall heat transfer coefficient you now have AND the relative resistance to heat transfer of the steam side, vessel wall, and process side. Notice, I have assumed you have a jacketed vessel, but do not know for sure.

Good luck,
Latexman

 

[pmover]

to supplement Latexman's response, changing heat source medium from steam to water will impact exchanger size (increase in size). increase depends upon heat source medium temp.

also, the equation written for proposed hot water system should be mCpDeltaT. LMTD is used in conjunction with Q in determining overall UA for exchanger at design conditions.

again, insufficient data is provided to provide an adequate response. suggest obtaining original exchanger data from nameplate as a starting point for sizing replacement exchanger.

good luck!
-pmover