Hello AE,

I have some questions:

• What is the fastest and most efficient way to remove condensed water droplets from an enclosed and defined air mass? If it is already condensed, can it be that hard to remove? Sure, it'll take lower temps to get the same condensation as atmospheric.
• Are you just trying to pump water out of a half-atmosphere chamber? (pumping against a partial vacuum?)
• What is the volume of the enclosed and defined air mass?
• What is the temperature of this enclosed and defined air mass?
• What is the Material Of Construction (MOC) of the chamber?
• Is there anything keeping you from having forced convection in the chamber?

Your original post doesn't give enough information to give an intelligible answer. Unless you answer at least some of my questions, I can't give a productive answer.

Mike

Mike

Bullet 1 - difficulty Yes it is difficult to remove in under 10 seconds. Have you ever seen fog disappear into a pool of water in less than 10 seconds?

Bullet 2 - I am trying to remove a majority of the water droplets from the air mass (70-90% of the droplets), I am trying to turn the fog into a puddle of water which will settle at the bottom of the chamber and then I can easily remove the puddle due to gravity

Bullet 3 - the volume of the defined space is 1 cubic meter

Bullet 4 - the temperature will vary based upon environmental conditions it will range between -40 F to 115 F. You tell me if there is a temp. that would be optimal for ease of removal.

Bullet 5 - the material is still be decided upon, but it will be highly non conductive to heat. It will most likely NOT be metal. Maybe PVC, plastic, silicone, rubber..

Bullet 6 - No, in fact that is what mother nature does to accelerate precipitation. We could stick some sort of fan in the chamber to create turbulence and force collisions of small droplets ultimately creating larger and larger ones.

Thank you for giving this some thought. I look forward to your simple yet elegant recommendation.

Hi AE,

So, you have both condensed water and water vapor in the chamber.

Bullet 2 - I am trying to remove a majority of the water droplets from the air mass (70-90% of the droplets), I am trying to turn the fog into a puddle of water which will settle at the bottom of the chamber and then I can easily remove the puddle due to gravity.

If the pressure in the chamber is only 500 mba (~0.5 Atmosphere); , there is no way to drain the water by gravity. Without using a pump or a generated vacuum, you won't be able to remove the water.

It would probably elicit better answers if you told us exactly what you are trying to do.

Mike

In the Himalayan mountains, communities are harvesting drinking water from mountain fog. The process involved hanging fine mesh vertically, and collecting the water that forms on the mesh in a collector something like a rainwater gutter. Something like that might work in the above case.

For further details, contact the WaterAid charity via their website.

Thanks for the comment, but this disregards my expressed NEED of quickly removing the water. Your suggestion though it is simple and natural takes hours to remove the water and that is unacceptable in my situation. Do you have any other simple, but faster suggestions?

The original thread has been posted in the New Technologies and Research section. Existing Technology may be found elsewhere.

I posted here because I was hoping that there might be some nano technology or some other solution in search of a problem that was just coming to market. Can I pick up this question and then post it on another forum at a later date?

GA and I rated it as one.

The only chance I can see for achieving the ends posted is to coalesce the droplets into larger ones and allow gravity or pseudo-gravitational forces to quickly separate the water. That implies either centrifugal motion type separators or impingement of the fog onto baffles.

Good answer, this is probably the easiest solution in my mind. What about a typical 2 phase separator with either a chevron pack or a demister pad?

Betamachine,

I agree that the simplicity of a separator is very attractive to me and I have been investigating them via Thomas Directory. There are a lot of manufacturers and they don't make it easy to search for the ones that separate water vapor vs dust/other particulates from gas streams. Could you give me a little more explanation of what a Chevron pack or demister pad does? Maybe you could point me to a website or a manufacturer of the types of separators that you are suggesting? Thank you.

AE

Sure, a typical vertical separator will normally be set up so that the inlet mixed phase stream will enter about the middle of a separator vessel and come into contact with an inlet diverter plate that will have the largest droplets of liquid impinge against the plate and then fall into the holding section of the separator. The gas then travels up the separator and any liquid droplets large enough will fall out of the gas stream by gravity. The gas then contacts the demister pad, which is really just a brillo pad (for simplicity) and to pass through the pad, the gas must follow a "tortuous path" with many twists and turns. The momentum of the remaining liquid droplets causes them to impact the demister pad and coalesce into larger droplets and eventually they fall out of the pad and down into the holding section.

Velocity is the name of the game in these separators, there will be a critical velocity which is a function of the liquid and gas densities which will in turn size the diameter of the vessel. See section 7 of the GPSA book for more details on these vessels, both horizontal and vertical.

You can also use coalescing filters, which have a replaceable element in them that will further scrub fluid particles from the gas stream but these aren't necessary unless you really want to get all the liquid out of there (the smallest droplets). Two manufacturers I would suggest are:

Burgess-Manning

http://www.burgessmanning.com/gas_liquid_separators.php

Peerless

http://www.peerlessmfg.com

They seem to be owned by the same company now though...

Your application may be smaller than what these guys offer, but this will be a decent starting point. For tiny stuff, this may work (it is a coalescing filter):

http://www.swagelok.com/downloads/webcatalogs/EN/MS-02-82.pdf

Hope this helps you out.

Betamachine, DaveB, Agua_Doc,

It appears that all the centrifugal separators operate via positive pressure differences. Meaning that the whole system is operating at a pressure greater than atmospheric and that the pressure drives the air through the device. Do you think that these devices will work just as well if I attach a root blower on the outlet side and draw the air through the system, thus operating the system at less than atmospheric pressure. In my initial question I said that I would be operating the air at 500 mbs pressure (1/2 sea level pressure). I guess that I could create a closed loop system and then put a blower in line to create the air flow required for the separator. I just don't know if the devices can hold a vacuum. They seem pretty solid and don't look like they would implode. Do you think that they would work in a low pressure environment?

I will call the manufacturers next week to ask the question directly to them as well.

Thanks. AE

I should expect that the centrifugal system will work with any pressure differential (either positive or negative) as long as it is properly designed. You are correct though in that structural considerations must be closely looked at.

If your chamber could be shaped as a cylinder, then a piston having an o-ring at its periphery and a central portion of Gore Tex could be forced down the height of the cylinder, leaving the Gore Tex wet on it lower side. The air above would be free of water micro droplets, but would have some water vapor. The water could be squeegeed off the Gore Tex.

Vaguely like a French press coffee maker.

BTW "Guru" means only loads of posts, That, in turn, means we either stay up too late at night, are wasting time at work, or are unemployed. Most of us feel lucky if we can find our navels given a flashlight and a map.

Blink,

Thank you for the suggestion. This is very similar to our approach up till now. We had been using brillo pad type material on a piston that could be vigorously moved back and forth inside the cylindrical chamber. The intention was to accelerate the collisions and coalescence of the water droplets onto the fibrous material of the brillo pad. The pad could then be spun to centrifugally spin the water to the walls of the cylinder. Your suggestion is to use the Gore tex fabric as a filter to capture the condensed water and sandwich it between the Gore tex piston and the end of the chamber. This seems worth a try to test the performance resluts.

AE

Introduce cold dry air

vaccum evaporation might be useful!!

Not sure what this means. Can you elaborate upon your suggestion?

AE

USE FOG DEMISTER AS USED IN CAR WINDSHIELD.

A cubic meter of air is not that much to deal with.

Have you considered displacing the saturated air by pumping dry air into the chamber?

L.J.

can you go past the -500 mb point?

if so then just reduce it as far as you can, this will dry the air all by itself. and then do whatever process you need to do,

If the process needs to be at -500 mb, then drag it down all the way to dry it, then re introduce dry air back in to the 500 mb point and there ya go.

Dropping the pressure will take the vapor to the dew point. Using a vacuum pump capable of pumping water or vapor will remove collected water and drop the chamber pressure to the dew point. If you want it to happen quickly, use a big honking piston chamber attached to the bottom of the chamber. Just don't drop it so quick or far to destroy your cloud chamber. I know this gets away from your -500mb parameter.

Another way may be to put an evaporator coil from an air conditioner in the chamber. Use the controls from an ice machine to dump freon quickly into the coil, and the vapor should condense on the coil and fall to the bottom. Once the cycle is complete, cycle the ice machine controls to evacuate the coil to prepare it for the next shot.

According to my dew point data, the lower the chamber temperatures are, the more difficult these processes will be.

Post 5 beat me to it, but I was not thinking of continuous process, but rather a "batch" job.

Either accelerating the chamber of gas/droplet mixture so that the inertia of the droplets impacts them onto the sides during acceleration and then deceleration of the chamber.

What would happen if the air container was "dropped" from a fixed height? Droplets would achieve a velocity, then the sudden stop would impact them onto the floor of the chamber.

Has anyone looked at "sonic" compression? A sound shock wave may cause dropletes to combine (similar to earlier attempts at rain-making with explosies in clouds).

I make these suggestions based on th ecriteria of "no contaminants" since all of these introduce no additional materials intot he system.

Possible solution for moisture problem:

In the air handling industry we use droplet eliminators to get moisture out of e.g. outdoor air coming into buildings. In figure 1 you see the eliminators made by Munters

Fig 1: droplet eliminators in air stream

The humid air is passing through the openings of the profiles and the droplets are caught in the "gutter" or "gutters" (depending on the shape of the eliminators) and the collected droplets will flow downwards were they are streaming into the drip pan.

Another solution might be the use of a "packet humidifier", were you don't use the humidifier as humidifier but the other way round.

Normally you place the unit in the air stream and by pouring water over the package this will become humid and the air that flows through it will become humid as well.

But if yuo use a dry package and send humid air through it, the package will become humid and if the package is saturated the fluid will stream into the drip pan.

Fig. 2 "package humidifier" from Munters

As solution nr.3 you could hang a lot of (cotton) threads from the top to the bottom ; they will catch the moisture, get saturated and the liquid will stream gently from top to bottom into a drip pan.

Good luck with your problem!!

Rien,

Thank you for the note. I think that you forgot to put your website link in the response. There are no figures which you refer to. Please include the figures that you refer to.

AE

Sorry for the loss of the figures, but hereby oyu can see the principle of the eliminator :

The package of the "package humidifier looks like this:

Hope to have helped you.

Kind regards,

Rien

Rien,

Thank you for the figures. I wound up finding them on your website. The first image is basically a vane separator (you stack them 1, 2, or 3 deep depending upon the needed water removal). The package humidifier is some sort of dessicant? I am familiar with all of the above solutions, but now know about your company.

If you have any new technology solutions that have not been discussed in this discussion thread then please send another note.

AE