Condensing Exchangers
Condensing Exchangers
(OP)
I need to calculate the U factor of a tube and shell heat exchanger which has a condensing process on the shell side.
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RE: Condensing Exchangers
RE: Condensing Exchangers
Regards
StoneCold
Regards
RE: Condensing Exchangers
The structure and phrasing of your question indicates that you have no background in sizing exchangers for condsensing service.
While overall "U" factors work for liquid to liquid service, sizing HXs for condensing service depends a lot on:
- Specific heat of condensing fluids
- Fluid film coefficents
- Tube sizing and spacing
- Ability of the HX to remove non-condensibles
and etc....
Pick up the Kerns classic HX text or go find Perry's Handbook of Chemical Engineering and start to read up
Try Chapter 3 of this book.....
http://www.wlv.com/products/databook/databook.pdf
.....and gimmie a star
-MJC
RE: Condensing Exchangers
Both process flow are petroleum based - tube side is heavy crude oil and shell side is naptha, a lighter derivative of the crude oil.
RE: Condensing Exchangers
If you know all four inlet and outlet temps, and the flow and heat capacity of your crude, then you can calculate:
Q=Cp*(To-Ti); shell side energy balance
U=Q/(A*LMTD); overall heat transfer equation
where:
U=overall heat transfer coef
Q=duty
A=area (a constant)
Cp=heat capacity of your crude
To,Ti=crude outlet and inlet temp
LMTD=log mean temp difference (see referenced sources for definition and calculation using your four temperatures)
Of course an overall heat transfer coefficient may or may not track well over time depending on how constant it is through the exchanger. Condensing equipments are often conceptualized by zone analysis because the heat transfer in the condensing and subcooling portions of the exchanger may be vastly different- i.e. using different U's to calculate the required area in different zones of the exchanger which are then summed for the total area requirement. Still, the ease of calculating an overall U makes your calculation efforts worth a try.
best wishes,
sshep
RE: Condensing Exchangers
RE: Condensing Exchangers
rmw
RE: Condensing Exchangers
RE: Condensing Exchangers
or you just do it with HYSYS.