8 replies to this topic

[rasik kirane]

Dear All,

Please let me know the criteria to decide how to install a Heat Exchanger/Condenser ? (i.e Horizontal or Vertical orientation of a Heat Exchanger/ Condenser)
What factors are involved in deciding the Vertical or Horizontal Installation ???

Regards,

Rasik

[Art Montemayor]

Rasik:

First and foremost, allow me to state that there is no general “rule of thumb”, criteria, or equation to determine whether a horizontal exchanger is better for your application than a vertical unit. Unfortunately (or fortunately) God has seen it fit and necessary for you to use the ingenuity and practical talents He invested in your person. In other words, the manner in which one determines which unit to employ is to study, calculate and re-study the application and its scope of work thoroughly in order to satisfy yourself that you are selecting the most practical and operable type. I will give you some examples to try to show you how a design engineer would go about deciding, but first you must fix certain parameters:

Is the unit a TEMA type shell and tube heat exchanger? If not, then the question is moot since orientation for a plate-and-frame or a spiral type is usually fixed by the fabricator.
Is the physical location limiting in available space or is the footprint a problem? If so, then you may not have a choice but to go with a vertical unit.

Example 1: A condenser that requires tubeside fluid to be condensing with shellside fluid to be vaporizing.
This is a classical case of BKU kettle and is a typical “no-brainer” with a mandatory horizontal orientation. The reason (of course) is that if you try to handle a condensate forming inside a vertical U-tube, you are going to have a hydraulic fiasco on your hands. It just won’t work hydraulically. More importantly, it is a configuration that is a maintenance nightmare. You can just imagine the problem of having to raise the U-tube bundle up and out of the shell (or drop it down). Horizontal configuration is the only workable option with the vapor introduced into the top of the tube bundle and condensate exiting the bottom outlet of the U-tubes.

Example 2: A condenser that requires subcooling of the product liquid.
This is often a case for the vertical configuration because if you can place the condensing phase in the shellside of a vertical, type BEM unit you can control a liquid level on the condensed liquid while you introduce vapor at the top of the shell. Depending on the level of the liquid, you can subcool the condensate formed before removing it if you circulate your cold stream in the tube side. Of course, you can also do a similar thing with a horizontal unit, but you will often find that you have to cover an excessive amount of tube area this way versus using the vertical orientation.

There are many other examples I could cite, but I hope you get the gist of what I am trying to demonstrate in being able to analyze in detail the operation that you want to bring about with ease, simplicity and effectiveness. All applications are not the same; you have to dedicate creative engineering time and effort into finding the best suited orientation and configuration for your case in hand. This involves a thorough process knowledge and background as well as mechanical – which is one of the reasons why I’m always demanding more and more mechanical preparation and knowledge from Chemical Engineers.

I hope this helps you out.

[rasik kirane]

Art,

Thanks for the patience you have shown to reply in this detail. I've understood what you are trying to explain.
Thanks again !

Regards,

Rasik

Vertical or Horizontal is based on structural considerations.Sub coolers are more effective in vertical positions.
We have several shell and tube heat exchangers ranging from 10 mt2 to 70 mt2 (Horizontal installations).The process fluid is generally organic vapors .The cooling fluid is CT water at about 27degC . The cooling water is passed inside the tubes in 2 or 4 passes .The process fluid is a single pass on shell side. Is there any advantage in terms Heat Transfer efficiency if vapors are passed on the shell side ?

parameswaran

[Technocrat]

dear all,

in case of horizontal condenser if you pass vapor on the shell side you can approach dropwise condensation which gives high value of overall heat transfer coeeficient, also the condensate will fall down easily leaving tubes bare for more condensation.

when you pass vapor on tube side, condensate forms a layer at the inside bottom of each tube hence lowering the heat transfer coefficient. you may install the condesner in inclined position towards the liquid outlet so as to drain out the condensate easily and hence to reduce the resistance for heat transfer .

regards.

[missbk]

Dear Art,
Please let me know a full selection guide of why and how to decide choosing a vertical or horizontal HE?
I am really confused about that.
As for the pressure drop, I find some way to calculate for shell side and tube side but very complicated, academic. I also know the imperial pressure drop about 5 - 15kPa but not clear, in case I have a higher viscosity or a boiling fluid in tube side, is there any imperial guide?

[djack77494]

Though some may cringe at the thought, a very general comment I would make is to use a horizontal orientation unless you have reason to do otherwise. I'd estimate that well over 90% of all the S&T heat exchangers I've ever seen are horizontal. Very smart from the viewpoint of pulling bundles and having easier access for maintenance purposes. Also, closer to the ground and therefore easier to support.

That said, there are a number of reasons to go with a vertical orientation. These may include thermal reasons (e.g. subcooling condensed vapors), hydraulic (thermosiphon reboilers) or space considerations.

HTH,
Doug

[missbk]

Hi Doug,
That's clear.
But still wonder, because i have been dealing with a real HE so I really want to know all the reasons lead to a vertical orientation. Got what you said: thermal reasons (e.g. subcooling condensed vapors), hydraulic (thermosiphon reboilers) or space considerations.
Is that all?
Thanks Doug,
Kim.

[djack77494]

Sorry it's taken me a while to get back to you, Kim. I was on a short vacation. In answer to your question, yes, that is about all. I can only think of one additional reason for going with a vertical exchanger besides those previously mentioned. My final reason is to achieve heat exchange control via level control of the shellside fluid. That would obviously be easier to do in a vertical exchanger. Still, it seems there are still quite a few legitamate reasons for going vertical - thermal, hydraulic, structural, space, control. Wow, even more than I imagined. What's left?
Doug