6 replies to this topic

[Vegeta]

Dears,

I'm working on a project in which viscous fuel oil needs to be cooled to a low temperature and hence high viscosity. The vendor has proposed a shell and tube exchanger with the fuel in the shell side and cooling water in tube side. After I reviewed thier thermal package I noticed that: the flow is laminar in the shell side ( Re is in the range of 1000), flow fraction B is about 50% while flow fraction E is 30% approximately, allowable shell side pressure drop is 30% utilized while it is fully utilized in the tube side, the exchanger is six tube passes and the baffles are single segmental. I felt that the exchanger was not optimized from the thermal performance analysis, so I regected the proposal.
My question is: what modifications and enhancements can I simulate (using HTRI) to improve this exchanger?
Also, from your experience what other types of heat exchanger are suitable for such service?

Regards,

[srfish]

What TEMA description did the vendor quote?

Edited by srfish, 20 September 2016 - 10:16 AM.

[Vegeta]

AES type

[srfish]

That is a good cleanable type.

[Pilesar]

Because you have a viscous shell side fluid, reduce the clearance between the shell and the baffles to lower your E stream bypassing. Examine the effect of increasing the baffle pitch and the effect of increasing the baffle cut on the overall performance of the exchanger since this will also reduce the flow of the E stream. Vibration will not be a problem with a viscous fluid, so you consider also increasing the clearance between the baffles and tubes. The goal is still to reduce the flow of the E stream which is not useful to the heat transfer. HTRI allows you to monitor the overall effects of each of these changes individually so don't make every change at once. You are looking for an optimal combination to try to reduce your E flow by half at least. If these things do not give enough improvement, your best option is to look at using two exchangers in series since you have plenty of shell-side pressure drop available. The two-exchanger design will have smaller shell diameters and each exchanger will have lower shell-side temperature change which should help significantly. The installation will likely cost more with two units even though the overall surface area will be reduced, but this may still be a better fit for the service.

[Napo]

Vegeta,

If you have a bit of time, please review the chapter 13: "Shell-and-tube Exchangers-the Pitfalls of Oversizing", of the book Process Design for Reliable Operations by Norman Lieberman.

 

On the other hand, you can take in account the BKU exchanger always in function of the operational variables and safety.

 

Napo.

[Guillaume Peltier NEXSON]

Dear,

 

For viscous fluids, the best is to get a unique single channel. Then SPHE from NEXSON GROUP (Spiral Heat Exchanger) solve laminar flow issue you get in a S&T.

This technology gets turbulent flow all long spiral core it will definetely improve your thermal efficiency. As a consequence much much more compact HTA than you the proposal you got.

 

Spiral Heat Exchanger is part of HTRI models, by HTRI doesn't provide full design, they offer you the posibility to check by yourself a quotation.

 

I advice to contact us on @ : http://www.nexson-gr..._9_lang_uk.html

Or you can email me in private.

 

Guillaume