Draining of heat exhanger 2

[sider]

In one of the CHW projects, I had to deal with a cooling unit heat exchanger whose IN/OUT connections were located in the middle of its overall height. After the hydro test, the heat exchanger could not be drained properly, as shown in the picture, as the lower part of it would be flooded since the drain is not located at the lowest point.

Problem

Exchanger Type

Does anybody have any idea how this could be done?

 

[LittleInch]

I think everyone here is just asking the sort of questions that maybe should have been asked during design / BEFORE this seemingly actually constructed.

If you're worried about contaminating the HX with any oil, just get hold of a nitrogen bottle, set the regulator to less than 16 bar and just blow all the water out. Remember to take care over asphyxiation / oxygen monitors of you're doing this inside, but really this sort of thing should be picked up in design / commissioning reviews before construction and testing.

Or just pump a load of glycol in it and deliver it half full of glycol?

And the question you haven't asked is how you actually fill the top half unless there's a vent there? Those end parts look suspiciously like headers to me , not a continuous coil, but maybe you can see more than we can? One drawing isn't a lot to base any discussions on.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[sider]

I think everyone here is just asking the sort of questions that maybe should have been asked during design / BEFORE this seemingly actually constructed.

I can totally agree with this one, however, such decisions are outside of my reach as my job is only to integrate this unit into the system.

If you're worried about contaminating the HX with any oil, just get hold of a nitrogen bottle, set the regulator to less than 16 bar and just blow all the water out. Remember to take care over asphyxiation / oxygen monitors of you're doing this inside, but really this sort of thing should be picked up in design / commissioning reviews before construction and testing.

I see your intention here, will check out this possibility. Would the even better option be to have some sort of preheater on the exit of the bottle, and to heat up nitrogen to purge and dry at the same time?

Or just pump a load of glycol in it and deliver it half full of glycol?

This is usual approach before transport...I just specify certain amount of glycol to ensure no freezing.

And the question you haven't asked is how you actually fill the top half unless there's a vent there? Those end parts look suspiciously like headers to me , not a continuous coil, but maybe you can see more than we can? One drawing isn't a lot to base any discussions on.

I agree, will look more into it as right now I dont have coil design.

 

[LittleInch]

If you can heat the N2 then that would be a lot better, but bottled N2 is very dry so you can use it to dry out the HX if you blow enough N2 through it.

A coil design and connection is required to take this any further, both for you and us.

As an aside does the airflow come in from the side then vent upwards?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[3DDave]

1) Consider a fixture to rotate the assembled unit to an orientation so it will drain correctly.

2) I am curious - it looks like there are header pipes. If so, a small diameter silicone rubber tube with a magnet on the end could be drawn with another magnet into one of the headers to a place to suction the bulk of the water out. As above, tilting the unit towards that header would encourage the water to exit more easily. I would also suggest a small amount** of alcohol be added just before using that plastic tube to eliminate the surface tension of the water - pour it into the tube on the other side from where the extraction will take place before tilting the unit. Just a few degrees tilt is all that is required.


**small, like one ounce per gallon. There are other surfactants, but I am not in that business to know ones that will certainly evaporate. I know that isopropyl alcohol worked great when I had surface tension trapping air bubbles in a thin tube - water flow would just drive around the bubbles and the ability to stick in the tube was more than the buoyancy. A soap would also have worked to lower the surface tension and then would have potentially caused more problems for me.

 

[shvet]

Unfortunately, the HE cant be reached (in front are filters, fan module, electrical connections, etc) which have to be disassembled (lot of resources necessary).

You have shared in this topic 3 pictures of HE for cooling of warm air by some liquid. And after this you say that an air cooler which cools hot air down cannot be warmed up by e.g. hot air because of confined space. Confined space?! A has been designed to contact with B, but after A has been manufactured it cannot come in contact with B because there is no enough space. What?

Could you elaborate please, sot sure do I get this right

Pay attention to bends. Liquid side of HE has been made of a continual non-branching smooth tube.

It means that a small flexible hose can be push in and travel all the way from input to output nozzles. When end of hose comes to the lowest point of HE you can fill hose with water => you provide siphon => liquid will self-drain from opposite end of hose. Google "siphon".

for info - pressure swing is widely used for evacuation of most part of hydrotest water from underground pipes and similar. Note that rupture membrane (preferred) or rapid-open valve should be used to provide enough velocity.

https://www.youtube.com/watch?v=6kHhsEUwRPg

https://www.youtube.com/watch?v=EU29BAQS0i8

Pig also is an option if you are ready take a risk it gets stuck in one of bends.

 

[pierreick]

Hi,
You may be able to flush the HX with air or better N2, this kind of procedure is often applied for draining coil/jacket on reactors when we change from steam to cooling water.
Should be a SOP.
My view.
Pierre

 

[FMJalink]

Dear sider,

Looking at the drawing you provided, the heat exchanger appears to be an evaporator for liquidized gas. Having a vapor cap in the top section. The drawing also gives the impression that the tubes are running horizontally and are connected on both sides to headers. This would make draining after hydro test, having the heat exchanger installed in the package/unit, indeed very difficult.

The discharge line shows a drain connection. Most likely in order to remove not evaporating liquids. Such liquids will also built up in the bottom of the heat exchanger, but will be very difficult to remove once the unit is installed. Client could be advised to install a drain connection on the lower part of the header(s).Would solve your problem, as already suggested in a posting above, and prevent future problems for your client.

Method to address this does depend on whether the design comes from your client or from your company.

Good luck with finding a solution,
FMJalink