INLET PROCESS TEMP LIMIT TO WATER COOLER

[roker]

Hello,

In a shell and tube heat exchanger with cooling water on tube side, inlet at 30 C (3 barg) can we expect operation problems due to high inlet process temperature (in our case 100 C), like local buubles, vapor lock, in the cooling water side.

regards,
roker

 

[sshep]

If your cooling water flow is designed reasonably then the bulk dT accross the Hx will not be a problem. You won't need to fear vaporization of CW, non-condensible build up etc. In any event it is always nice to use a flow up design on the cw side where possible to avoid vapor pocket problems (especially filling at start-up).

What you truly do need to be careful of is high tubewall temperature which can scale reducing the cw flow, heat transfer, and lead to underdeposit corrosion. What is on the shellside?- these properties also affect tube wall temperature and scaling tendency. I have seen blowdown exchangers with the tubes (cw) scaled completely shut by process temperatures of 100C, and others like condensers do fine. Perhaps you have an example of scaling problems with the actual cw in question in a similar service.

best wishes,
sshep

 

[TD2K]

You won't get bubbles or vapor lock. If your incoming gas is 100C, your cooling water (assuming you are at sea level) won't start to boil till you get the bulk temperature up to 100C. Since cooling water systems are usually pressured to some extent, you can eliminate that concern.

However, you could have a problem with scaling and fouling on the tubes depending on the cooling water quality and treatment program. Some companies just limit the cooling water exit temperature, others will not allow cooling water to be used in services over a certain inlet fluid temperature that you are cooling (the former is a more common constraint than the latter in my experience). 100C doesn't seem terribly high, I'd check my exchanger design to see what the corresponding tube wall temperature is predicted to be and ensure I have adequate cooling water velocity.

 

[DYV1973]

If your process side is also a fluid (and suitable for it), you might consider using a plate HE. As shear rate over the plates is higher, and more turbulence is created, the risk of scaling will reduce.
Since also the plate material of a PHE is at least stainless steel, you can also consider a CIP-ing procedure with a light acid with a flow opposite to the normal CW flow.