suggestion required for shell and tube exch 1

[vesselguy]

Hi,

I'm having some trouble finding a workable solution for my s&t thermal run in HTRI and would like to get some suggestion for a configuration. I have a water-water exchanger with one stream having only a mass flow rate of 1/4 of the other. I am using a BEM and put the high flow steam in the shell and split the flow in parallel to reduce the shell side stream velocity and to minimize the vibration. the problem now is the tube side velocity is extremly low. I've tried a single shell BHM and got some improment but still getting a tube velocity of 0.2m/s. Too low. Can I please get some suggestions? Thanks.

 

[rmw]

What happens when you put the high flow tubeside?

rmw

 

[Christine74]

Some suggestions:

1) Increase the number of tube-side passes (max. is approximately D/2.5 where D is in inches)

2) Use smaller diameter tubes (don't go below 3/4" for cooling water)

3) Use wire matrix inserts inside the tubes.

4) Use low-fin tubes instead of bare tubes, since this would reduce your required surface area by roughly one-half. To reduce vibration potential, consider using NTIW or double-segmental baffles.

-Christine

 

[vesselguy]

Hi Christine,
Prior to posting my question, I had tried increasing the number of tube passes. I can't go any longer than 60 feet on my tube length. I am already using 3/4" tubes. Operations folks don't like using inserts so that's out.

rmw,
I know it won't work but I did tried putting the high flow in tube side. The velocity of low flow stream in shell side is even lower and of course the velocity of the high flow stream is well past erosional limit.

Thanks to both folks who posted in response to my question.

 

[srfish]

Normal practice is to follow the suggestion of rmw and put the low flow in the shell. In this case if the erosional limit inside the tubes is 12 ft/sec and the shell flow is 1/4 of the tube velocity, then the shell velocity is 3 ft/sec. 3 ft/sec water velocity in the shell side gives good heat transfer.

srfish

 

[MJCronin]

Ummmm.... perhaps a TEMA BEM is the wrong thermal solution..

What is the approach of this particular HX problem.... are you beyond the limits of what is reasonable for a S&T ?

Would a "plate-frame" HX solve the problem..??/

-MJC