Volume of Water

Where is the condensation?

1. Top half?

2. Bottom half?

3. Left half?

4. Right half?

bottom half

Is the water on the inside of the glass face? If so, dry it out and apply a bead of clear silicone caulk around glass edge and any other obvious openings. This should prevent water vapor from reentering and condensing.

It is inside face of the glass. No access to clean it. Looking for 2 part solution. 1. Trying to determine if there could be too much water condensing. Is there a way to calculate the volume of water that could be condensing? 2. We are selling hundreds of these enclosures. So, looking for a permanent solution. Do you think applying silicone would dry up after some time and would it need a periodical silicone application? Thanks C1

If you are selling hundreds of them, I'm assuming you are storing them. I would dehumidify the air where they are being stored. Once you are sure they are dry, apply the silicone caulk. No, silicone caulk will not dry out.

Try this on a couple of units and place them in a humid environment. If you don't get condensation, they are ready to ship and should be fine. You will have your solution.

Thanks much

I tried to look up silicone caulking. There are many kinds of it for sealing. I could not read if they could help/stop condensation. Can you suggest any specific brand?

These people make a good clear silicone sealant/caulk, but really any exterior clear silicone should work, or even a clear silicone made for around shower enclosures, etc. A little word of warning: It takes some practice to pull a nice bead of caulk. Cut your tip at 45° and start with a small cut. Good luck!

http://www.dowcorning.com/applications/search/default.aspx?R=2146EN

Just put couple of packs of silica gel(Desiccants) inside your product. This will absorbed the water vapor in your equipment.

That's simple n easy. Thanks. Do you think that I might require to replace these gel packets often? Do they expire? I hope they don't expire and is a permanent solution.

If the enclosure of your product is perfectly closed, i think no need to replace it. Read something more on packaging, most of the products are being packed at a maintained Nitrogen surrounding, where moisture is not significant, or perhaps pack in dry air surrounding.

Or minimized the exposure of the glass LCD monitor/display to ambient air, this will mean have the design of that part closed not to interact with ambient air.

Silica-Gel packs do have a limit on how much water they can absorb. Perhaps a small tray designed into the product to facilitate replacement. They can also be "recharged" by placing them in an oven set at about 250 Deg. F.

Thanks for giving relative examples. I wonder how they fixed that auutomonile headlight water issue. Can you share any details of the solution. From your post I understand that a porous gasket was used to keep air circulation. Do you think usage of a closed cell gasket or solid rubber gasket might be a resin for condensation?

This looks like a game of 20/40/60... questions before meaningful data are given.

Dear Mr.CADone,

The reason is simple and related to PSYCHROMETRIC aspect involving RELATIVE HUMIDITY and DEW-POINT, related to THERMO DYNAMICS.

From your expression, I understand that the air/water vapour is concealed in the equipment . If so the following is the explanation.

In the night hours the ambient/atmospheric temperature comes down. As a result the RELATIVE HUMIDITY INCREASES WITH IN THE EQUIPMENT. When the vapour reaches the Saturation Temperature the vapour condenses and deposited as mist/dew

WHEN THE DAY TEMPERATURE RISES, the RELATIVE HUMIDITY FALLS INSIDE the equipment (as in the Atmosphere) and the condensed particles get evaporated and vanishes.

This process repeats ever day. To solve this problem, moisture content of air is to be removed . Provision of Heater may be risky if temp. is not controlled.

DHAYANANDHAN.S, INDIA

Dahayanandan & Just an engineer have answered your question well, but perhaps to convert this to an easy solution. The essential problem is that warm air can carry a lot of moisture, and this will condense out when either that air cools and or when it comes into contact with a cool surface (in your case the glass).

All this is explained by reference to psychometric chart, and that the "offending air" is drawn in and pushed out each day by its expansion and contraction with the temperature rise and fall each day.

There are at least four solutions - and I recommend the last.

1. place a moisture absorbing substance in the cabinet to keep the air moisture content low.

2. maintain the temperature of the air outside the cabinet (and so also inside) so that there is no chance for the moisture in the air to condense out.

3. cool the air outside the cabinet to force much of the moisture out of the air, and then reheat if necessary. This is a standard dehumidifcation process.

4. What I recommend though (as it seems to fit your circumstance) is just to ventilate the top (and bottom) of the display cabinet. This way any hot air will rise, and it will be replaced by cooler air with less moisture. The effect will be to pump moisture out of the cabinet and always have the air inside the same temperature as the outside so that there will be no condensation.

Dear Mr.TreyorM,

Thanks for your comments.

DHAYANANDHAN.S., INDIA

Your solution is air movement. You don't have enough.

this is a small 50W silicone pad heater..

I've used this type of heating element exterior stand alone displays.

Low voltage units are also available. They are have an adhesive to stick them to a drum of oil or a metal plate etc..

...For myself .. I prefer a well sealed electronics enclosure that also has some ventilation.. 1/8" weep holes in the bottom if they aren't there already..

No holes big enough for bugs.. or hole open enough for driving rain.. but enough to let the air inside stay dry through convection.

...is there enough wasted heat in the product to keep it dry during operating conditions? Is the display 24/7 .. would you need timers or thermostats?

some considerations..

..and always ship with the silica packets inside the units..

who gave me an "off topic"?

why?

call me curious

It was me. It was an accident. I actually wanted to rate it otherwise. Sorry.

Allow me to fix that then.

I didn't understand what you mean. How can I fix that? Let me know please. I have marked 2 responses incorrectly. It was late when I realized that.

I used my vote to neutralize your 'mistake vote' - that's all.

In this system you cannot vote twice on a post.

So, make a mistake and only Admin, or another member, can 'un-vote' it.

Voting is complicated, due to the wording changing in the voting 'drop-down', depending on what sort of vote was cast first. (GA or OT)

Many make mistakes when the 'double negative' appears.

High English skills are needed to follow these changes in wording and 'tick' order.

I don't mean "High" among 'English as a second language speakers' - I mean "High for English is my only language speakers.

Many regularly get it wrong.

But, as it is Your Thread, you can contact Admin and ask them to fix your errors.

You can also ask Admin for help with any aspect of the thread 'content' or poster 'attitude'.

You can do this most easily via the 'Report' button, which connects straight to the moderator on duty. Type your 'problem' and they should respond/reply to your CR4 mail box.

Thanks 34point5

All the solutions are very impressive.

I am sure there might be some water accumulating. Is there a way we can figure out (Calculate) how much minimum water must be accumilated for having the half of the 3' glass covered by water condensation?

Sure; area times thickness of water times density of water. Determining the average thickness is the tough part.

--Tornado

Let me ask it a little differently. Its probably more of a math question.

I am trying to prepare my data before I actually implement a remedy.

I need to know ; in this display which is a basically hallow cylinder of 3feet dia x 6 in thick. How much water could be trapped in the all the air inside this.

I am wondering that it might be possible that its not just the water accumulated on the glass.

I need to present this problem-data-solution to my management. With everybody's help I do have quite a good solution, but would also need to provide theoretical data.

Heaters will NOT solve your problem. You need air circulation or the vapor cycle will continue forever.

As Dhayanandhan mentioned earlier, this is psychrometrics. You find the point on the chart matching your temperature and relative humidity (which is 100% since there is condensation), and then read off how much moisture there is per pound of air. The chart also tells how many cubic feet of air per pound.

guys I tried to use the graph. It had 5 0r 6 variables. I got confused to use it. Here is a another approch i found online. What do you think of this. reference : http://boards.straightdope.com/sdmb/archive/index.php/t-352143.html In my case : I am trying to calculate the total volume of water possibly present in the air in the container. 3ft dia by 6in thk. Ambient temp 70 Deg F = 21.1 Deg C From chart, Absolute Humidity = 8.7 g/m3 @ 50% Humidity Volume of Cylinder = ( Cyl 3ft dia, 6 in thick) 4.25 ft3 = 0.120 m3 8.7 X 0.120 = 1.04 gm = 0.03 oz Is this correct ?

That's the right approach, but because of the condensation you need to use 100%RH.

Do you mean the approach I used is OK with RH chosen as 100%?

I gather this is an all metal and glass construction, so moisture from wood glues, or similar, is not a cause. If you are using sealant on the glass, evaporation of volatiles may be a cause.

If coolants are used in manufacture, you may have trapped pockets evaporating and condensing coolant.

Similarly if it has beep electroplated liquids can be trapped between spot welded surfaces, or in tubular, box section, folded returns and similar voids.

Heating will obviously speed the evaporation - but you need to purge the humid air to 'dry out' the interior. Or as some mentioned, use a desiccant.

However the condensate could be light oils, solvents, wetting agents and similar used in coolants, or sealants, which a desiccant won't capture.

You mention it has 'drain holes' in the bottom - I would suggest you also need air vents in the top, to let whatever this is out.

You may, or may not, need permanent heating if this is 'moisture from manufacturing'. But it could also be that some evaporate has left a hygroscopic coating that is adding to the problem.

But a warmer than ambient object will not attract condensation. And heat plus vents will induced moisture to just circulate through the unit and exit the top vents, by convection.

_{Apologies to any that have covered the above - as I've only had time to skim the posts}

CADone - have you found a solution yet? I came late to this issue but interested in the subject.

During my time with Veeder Root in Dundee we had an agricultural counter that sat on the back of a tractor. The 'window made of glass' used to get misted up and the numbers could not be read.

We tried a lot of tests to simulate the situation and it was evident that temperature cycling is the reason for misting or condensation. You will probably find plenty of condensation on the metal part too - as you are concerned about the glass only at present. We also worked on a product that cannot tolerate any condensation and that has to be filled with dry Nitrogen of dry helium depending on the application but the container needs to be hermetically sealed.

If I understand you have a 'sealed container' and seal is not hermetic. You do not take any precautions to ensure that there is no water vapour left to cause a dew point in the temperature ranges that the container is subjected to.

Please let me know if you are still interested to resolve this or if you have found a solution.