Main Condenser/ Vent condenser surface area relation 1

[MedicineEng]

Dear All:
Tipically the area of the area of a vent condenser is around 20/25% of the area of the main condenser (relation 5:1).
If I use a vent condenser as big as 80% of the surface area of the main condenser (relation 1,2:1) which are the operational problems that you anticipate?
Did any of you already worked in this situation?

Thanks for your help.

 

[Montemayor]

There is no relationship between the heat transfer area of a main condenser and a vent condenser - unless you are dealing with a SPECIFIC APPLICATION that is repeated in different locations. You haven't stated that, so your general statement is wrong the way it is written.

There is no general, "quickie" relationships or formulas for in-experienced persons to apply process heat transfer technology. You must be trained in, experienced knowledgeable in process heat transfer. If you are not a professional and experienced engineer who possesses those requirements, the job should be left to one who does.

Condensation can be carried out in a variety of condenser configurations; it can be partial or total; it can be for producing saturated liquid products or for sub-cooling; it can be or distillation reflux purposes or for enviromental or vapor recovery purposes. There are just too many variables to take into consideration in one Forum thread.
I have designed, built, installed, and operated most of these applications and it would seem that you are assuming that what you assert is perfectly true and that you are certain that your application or design is correct. If so, you are of course free to employ whatever you consider correct and safe. However, based on what you assert and the lack of specific information, it would seem you are going about this in a totally wrong manner.

 

[25362]

You don't say what it is you are condensing: steam, hydrocarbons, etc. If, for example, it is steam, I think an oversized S&T condenser (main or vent) using cooling water could lead to greater amounts of dissolved air due to possible condensate subcooling either by reduced loads or when in the winter season. Could this be a problem in your case ?

 

[MedicineEng]

Dear All:
Maybe I didn't explain myself in the better way in my initial thread. My apologies for that.
Trying to rephrase my problem and adding some more clarifications:
-This is a condenser system in a reactor that distil hydrocarbons;
-In the past, it was reported by Production that this condenser system was insufficient to condense all the vapours and there was still traces of hydrocarbons in the form of vapour (smell) and in the discharge water of the liquid ring vacuum pumps;
-Recently we had a problem in the vent condenser that demands its replacement;

I saw here an opportunity to improve the system by adding a bigger vent condenser instead of just buying the same that was previously installed. This is a practice that I am been following: everytime that we have an equipment that needs full replacement I try to reassess the process to see what can be improved, instead of just follwoing what was installed and repeat eventual errors in the initial design.
When I was reassessing this installation I realized that the ratio between main/vent area was 4:1 and compared with the other installed system that we have here. They all follow the "ratio rule" of 4(or5):1. As this ratio proved insufficient I was trying to see if in operation terms there is any issue that I should worry about by decreasing this ratio to for instance 2:1.
The only thing that I could think of was a colder return on the condensed vapours, but this is not a issue for us.
I am in contact with the manufacturer to obtain the best solution, but I would like to hear from someone independent and with field experience if I can expect any operational problem.

 

[rmw]

Condenser and S&T heat exchanger are not necessarily synonymous.

rmw

 

[MedicineEng]

These are not S&T condensers, are annular groove graphite condensers.

 

[StoneCold]

Let me start out with saying I have absolutely no experience with these annular grove graphite condensers. That being said if it was my problem I would try to figure out how much heat transfer I am getting in the main condenser. If the main condenser is not fouled or getting poor utility flow for some other reason then I might consider making the secondary condenser larger. However you need to do your field work on these types of things. Sometimes your utility supply lines are plugged or the pressure is to low and you are getting lousy heat transfer. No amount of exta heat exchange area is going to fix that.

Montemayor is right about the ratio situation. While it may be an interesting fact I would not use that to size the next heat exchanger. Try to get some hard data to the exchanger supplier and go from there.

Regards
Stonecold