Flow profile in the tube side of heat exchanger

Question

Flow profile in the tube side of heat exchanger

C4Reactor (Chemical)

(OP)

11 Jan 03 05:42

Experiencing fouling at the tube side (Cooling Water) of a heat exchanger. The HX is of straight tubes with a longitudal baffle at the channel cover to allow for two passes design (TEMA type: BEP).
Cooling water enters thru the bottom nozzle of the channel cover, flow thru the tubes and return to exit at the top nozzle of the channel cover. Hot vapour enters from the shell top nozzle.
Fouling at the CW side observed at the top tubes only. CW flowrate registered at the inlet piping is above 1.8 m/s. At this rate the fouling is unexpected.

Understood that the relatively hot section at the top shell will lead to fouling in the top tubes. But a question to the group, for this type of HX:

1. Will the CW flow velocity in each of the tubes the same? Is it possible that the top tubes are having a lower flow velocity, due to the design, which further contributes to the deposition.

2. If we use a U-tubes design, will the occurance be the same?

Appreciate any comment

Samiran (Chemical) · Answer 1 · 2003-01-11 06:04:02

Well I think you'd expect fouling in the top section depending on the water quality. Carbonates would tend to precipitate at hotter temp. Solutions could be frequent backflushing or chemical injection.
I dont think velocities will be different. Why do you think U-tube would be better ? This will make cleaning of insides of the tubes more difficult.

Samiran

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Flow profile in the tube side of heat exchanger