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Heat Exchanger
#1
Posted 26 May 2016 - 04:39 AM
#2
Posted 26 May 2016 - 05:17 AM
Hi,
In general, yes...because looking at thermal standpoint, it's more effective than the contrary...
But there might be exceptions to force doing vice versa...
#3
Posted 26 May 2016 - 04:38 PM
#4
Posted 27 May 2016 - 02:40 AM
Sometimes it is prefered to put the high pressure stream in the tubes. This will minimize the amount of material required to withstand this high pressure if compared to putting the high pressure stream in the shell side. Consequently, this will lead to cost reduction.
CheAmine
#5
Posted 02 June 2016 - 07:10 AM
#6
Posted 02 June 2016 - 07:58 AM
No, not always. It depends on the process, what fluids you are considering, if the fluids are corrosive, operating & design pressures etc. etc.
For example, an LNG shell and tube heat exchanger would have LNG on the tubeside (cold), with typically hot water/glycol on the shellside.
As to what you are looking to design:
What fluids are you considering?
Operating pressures?
Flowrates?
Inlet temperatures / required outlet temperatures?
Where are you getting the Kerns method from? E.g. in Coulson & Richardsons there is a step by step example of it?
#7
Posted 02 June 2016 - 08:08 AM
Hi ,
A few documents for you and others interested with the subject .
Enjoy.
Breizh
#8
Posted 02 June 2016 - 09:15 AM
Yes IGC am actually using C AND R vol6, my confusion all started in the very first example (12.1) I understood it up to a certain point bt my confusion started where they said U=600w/m2k (they quoted fig 12.1 to get this value bt i dnt get hw it was choosen).
Also my next confusion was the basis on which they choosed the outer and inner diameter to be 20 and 16mm respectively from there downwards was were I stopped understanding what they were doing...
I know my questions may seem elementary am just a Young chemical engineering student with a zeal to learn...ur prompt responses would be really appreciated...Tanx
Edited by emmanuelv2012, 02 June 2016 - 09:15 AM.
#9
Posted 02 June 2016 - 10:10 AM
The Kern method is iterative, that is that you make initial assumptions and then based on your calculations, you go back and repeat until you have a more reasonable answer. The U = 600 w/m2k comes from figure 12.1. Your process fluid is the condensing organic vapour, while the service fluid is the river/well/sea water. Drawing a straight line between them gives you an estimate for the overall heat transfer coefficient - in this case, around 600 W/m2k. This is just a guess to get you started.
Tubing is based on OD, with a certain wall thickness. In this case 20 mm OD with 2 mm wall thickness, which gives you 16 mm ID. The process fluid has to flow through something! Again, it is just a guess for the example. They could have easily chosen 1" or 0.5" tubing. It all becomes a bit of a balancing act trying to get the most efficient cost / performance balance. If you were to make up the required surface area with 1" tubing, you'll most likely end up with a larger shell diameter -> more material -> more expensive.
#10
Posted 02 June 2016 - 11:27 AM
#11
Posted 03 June 2016 - 08:59 AM
bt pls which is process fluid and which one is service fluid??
And please how did they arrive at that 4.88m used as d length?
Edited by emmanuelv2012, 03 June 2016 - 09:05 AM.
#12
Posted 06 June 2016 - 01:39 PM
Hi Emmanuel
I could not understand your question. What do you mean by process fluid and service fluid ? Also are you referring to some specific case with 4.88m as the length ?
#13
Posted 08 June 2016 - 10:02 AM
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