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In one of our new projects, we have a shell and tube heat exchanger for crude heating from about 15 C to some 70 C using hot water as heating medium. This crude exchanger is located downstream of 1st stage production separator in the stabilization train. The crude is specified to be on shell side, whilst the hot water to be on tube side. (Please note we also have an existing installation where crude is on the shell side and water on tube side, operating for last 15 years without any issues).
However, EPC contractor is now proposing to swap the fluid i.e. crude in tubes and water on shell side.
Any feedback on the subject will be useful, so as to make a right selection of design with respect to both engineering and operating /maintenance considerations.
 
Answers
16/03/2009 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
For those suggesting Koch twisted tube technology: excellent design... but please be mindful of the fact that should tenacious deposits form on the shell side it would require specialist cleaning technology to access the "cleaning lanes", which I believe is unique to Tubetech.
15/03/2009 A: KengYong Chan, Air Products & Chemicals, Inc, chanky@apci.com
Suggest to do a detailed HX simulation if modeling tools are readily available to compare the process parameters changes.
One of the process considerations will be the larger dP for the tube side fluid and any hydraulics constraint downstream when crude is switched to tube side.
Another consideration will be the pressure rating of the tube/shell side based on the maximum pressure of the crude/water. This may require re-rating of the equipment or higher design rating tube/tube sheet and shell.
Lastly, I would go for a similar go-by approach per the existing S/T HX which you do not have any issues for the past 15 years, unless process simulation can demonstrate there is an efficiency or benefit in switching.
13/03/2009 A: Alan Goelzer, Jacobs Consultancy, alan.goelzer@jacobs.com
I am assuming that hot water loop is using high purity water with less than say 20 wppm residual TDS and corrosion inhibitors and no glycol or other "anti-freeze". This strongly favors keeping the water on the tube side. Low TDS hot water circulating at suitable velocity in the tubes can give heat transfer coefficient similar to "clean" low-pressure saturated or superheated steam.
Crude oils tend to be relatively viscous between 15C to 50C or so, so the shell side of this S&T exchanger should be configured using an appropriate version of "helical baffles" or perhaps alternatively BFT Twisted Tube Technology.
Fouling and thermal performance can be severe if using traditional baffle types due to formation of stagnant zones and streamline pathways for the more viscous and often somewhat non-Newtonian crude oil.
13/03/2009 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
Square pitch exchangers can now be cleaned mechanically and unblocked whether with Crude / coke like deposits or Polymers See: www.tubetech.com/vcfe-shell-and-tube-side-clean.asp
Tube side cleaning is never a problem with crude and is easier than cleaning the shell side of triangular pitch exchangers
13/03/2009 A: Eric Vetters, ProCorr Consulting Services, ewvetters@yahoo.com
Typically the more corrosive or higher fouling fluid is put in the tubes. If the more corrosive fluid is on the shell side both the shell and tubes typically need upgraded metallurgy. For fouling services it is typically easier to hydroblast the tubes than to clean the shell side of the exchanger.
13/03/2009 A: Samuel Sinanan, IPSL, Samuel.Sinanan@ipsl.co.tt
Usually the more corrosive or fouling fluid is designated for the tube side because the ease of cleaning. In this case, without knowing the properties of the crude the may be deemed more corrosive to the EPC contractor. Also, the EPC contractor may have decided to go this way if the heat exchanger duty is greater by swapping. A simulation of the heat exchanger may confirm this.