water cooling with tap water?

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steve_rb
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water cooling with tap water?

Post by steve_rb »

I have connected RF generator, Matchbox and coil water cooling all to one small aquarium pump submerged inside a bucket full of tap water. Flow is OK for all three. I was windering could using tap water may cause resistive connection between these three and affect matching point? Or could it have possible other effects ?
Jerry Biehler
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Re: water cooling with tap water?

Post by Jerry Biehler »

Its usually best to avoid tap water if for no reason other than deposits on internal lines and the like.
steve_rb
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Re: water cooling with tap water?

Post by steve_rb »

I wouldn't worry about deposites because I am using a closed loop water inside a bucket and not running water. Only a little deposit will be there initially and will stop later. But I am talking about water conductivity. Even if I use distilled water still conductivity will be there unless DI (demonized) water being used. For target cooling I will use DI water but for cooling RF, Matchbox and coil I don't think DI water is needed. Only tap water for short time tests and distilled water for long time operation should be OK. That is why I want to know other's opinion about this.
Linda Haile
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Re: water cooling with tap water?

Post by Linda Haile »

I'm aware of some recent as yet unexplained effects using tap water and ethylene glycol etc to cool RF coils etc. where there can be some as yet unexplained deposits on the return side of the system, but these don't seem to be detrimental to the process.

Can anyone suggest how the RF may be causing this? or any other theories?

Should I start a new thread?
richnormand
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Re: water cooling with tap water?

Post by richnormand »

Hi Steve,

Depends what is your objective: low conductivity or stability and corrosion control.

I have been using real DI (de-ionized) water with a inline activated resin filter for high voltage laser flash lamp cooling. The resin filter keeps the impurities and conductivity under control. I have to change it every two years or so due to flow blockage.

For the RF induction heater (not that different than your setup. I use water from jugs for drinking fountain from the grocery store that is done thru reverse osmosis (says so on the jug label and is almost as good as distilled water for conductivity) mixed with ethylene glycol antifreeze. No funny deposits apart from a bit of whitish residue inside the copper tubes. The antifreeze has chemicals to deal with the dissimilar metals and prevent corrosion. Seems to work well.

Both setups are closed loop with a water to air heat exchanger.

Now in your case you state “use distilled water still conductivity will be there unless DI (demonized) water being used”. Well if the water is demonized then you could use an exorcist and you’ll be OK….
steve_rb
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Re: water cooling with tap water?

Post by steve_rb »

I think I didn't make myself clear. I meant 3 loop of conductive water can cause a resistive connection (or shunt) between coil, matchbox and RF generator through coductive water. Since coil voltage can reach up to 2000 volts I thought will it affect resonance condition or will it cause damage to RF?
richnormand
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Re: water cooling with tap water?

Post by richnormand »

I looked inside the RF box. No cooling to the maching components but there are chokes and cap bypass for feedthoughs on the two water inlets to the coil (1/4" copper tubes) and the power supply wires to keep the RF inside and decouple the coolant and the outside world. If you mean the DC resistivity of the water then DI with a resin filter is all I can think of, but unfortunately DI water is pretty corosive.
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Doug Coulter
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Re: water cooling with tap water?

Post by Doug Coulter »

Unless you or your gear are allergic to it, try mineral oil. No deposits. No conductivity, and something I've not seen mentioned so far, but less than 1/10th the dielectric constant of water....so less shunt capacity. Yes, it's a mess. So is water in a bucket as we found when doing that game for cooling a diffusion pump -- things never fall *out* of the bucket, you know? And algae etc don't grow in oil, fed by the insects that get into buckets and die. You don't get as much cooling as with water, but you shouldn't need extreme cooling unless you're doing something extremely inefficient. Which in turn is a sign you're getting something else really wrong. Better to fix the disease than patch over the symptoms.
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Jerry Biehler
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Re: water cooling with tap water?

Post by Jerry Biehler »

Ethylene Glycol (Antifreeze) should never be used unless your shop drops below freezing. That stuff actually lowers the heat capacity of the cooling system and is only needed to prevent freezing.

I have a 5 stage RO/DI system. They are cheap. Less than $100.
DaveC
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Re: water cooling with tap water?

Post by DaveC »

Doug makes a very good recommendation.

Other than very high power, low voltage hardware cooling, (couple kV, low freq. and kW) oil or Fluorinert or equivalent cooling is usually the easiest and most satisfactory all around.

High resistivity, and breakdown strength, few ions,( if clean), and low dielectric constant make a winning combination. And.... you can get the stuff (mineral oil, at least) at the local pharmacy, usually.

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lutzhoffman
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Re: water cooling with tap water?

Post by lutzhoffman »

Why not use water? So long as your plumbing is SS, or copper you should be fine, as per the previous recomendations lowering of the mineral content is a good idea, but how this is done: Distilled, deionized, rev. osmosis etc. should not matter.

Where I grew up in Seattle tap water would be fine due to its very low mineral content, in Kentucky however where a friend of mine lives, I would not do it. A simple test would be to boil down a pot of water on the stove, if you have a bunch of crud left in the pot then you probably should not use the local tap water.

If your cooling system plumbing is all metal, RF effects should not happend at all since the inside is essentially a Faraday cage, and it should not see any potential. For a grounded system the anticorrosion additives sold for paint sprayer protection at the hardware store work fine also, if this is a concern.

For any water system bio-slime will happend sooner or later, even in laser systems which use de-ionized water, this still happens, do not ask me how life is simply amazing. They flush the laser cooling system with 15% H2O2 bi-monthly to eliminate it. Pool supply outfits have concentrated peroxide for sale, but wear gloves and goggles it burns your skin and eyes like acid.

If the cooling system is not grounded and at potential, then I would go with Doug's idea of just using flowing oil like in CT scanner X-ray tubes. Its cheap, simple, and effective. Just increase the flow rate some over water due to the lower specific heat. For real critical HV stuff like cooling ion sources at HV: Fluorinert, and Galden fluorocarbon fluids represent a very nice fill and forget solution, they are however expensive unless you pick it up on ebay.
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Doug Coulter
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Re: water cooling with tap water?

Post by Doug Coulter »

Lutz, I believe he needs insulating coolant which is why the question was asked. He's going to have RF across it. Else, yep, it's really hard to be plain old water for cooling, at least for the money in the coolant and fittings required.

Me, I hate plumbing, though I do it a fair amount, and being on solar power, am kind of an efficiency freak. So I mostly use variable speed fans on heatsinks conduction coupled to the heat source -- but as a last resort. In my "religion" if it needs power-cooling, why not get rid of the waste instead?

That's just my religion, of course. But if anyone is interested in Q rather than sheer size -- it's a nice church to be in.
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Dustinit
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Re: water cooling with tap water?

Post by Dustinit »

We make ICP instruments and all of the ones I have seen so far had the work coil cooled with water and seems common throughout the industry. I was concerned with water conducting the RF when I built my ICP oscillator but did not notice any conduction effects even at 2KW (~4kv Peak). I even tried ferrites on the water tubing to compare the system without and there was no difference. DC conduction is a different matter and would require a non conducting coolant or you will get cathode stripping / electrolysis/corrosion. I suspect the water resistance is too high to provide an appreciable current path to lower the Q or have any other noticible effects. This will be dependant on factors such as tubing length, ID and water conductivity but at 30cm tubing length 2mm ID with plain tap water I could not measure any change and feel this is something that you do not need to worry about.
Dustin.
steve_rb
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Re: water cooling with tap water?

Post by steve_rb »

Good. But still I prefer to use three seperate water circulating circuit in order to eliminate any possible water conductivity effects. I have to spend money for two extra water pump but using small aquarium pumps it is not too expensive.
lutzhoffman
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Re: water cooling with tap water?

Post by lutzhoffman »

Hello:

To correct my previous posting, I see now that you need an isulating fluid, so Doug's original response of using oil sounds the best to me. As a close second I would look for a fluorocarbon fluid like the Galden line, these can handle 40KV/mm so one cooling fluid loop, could cool everything if its build right.

These are pretty much fill and forget fluids. You can even put in an additional heat exchanger at different points in the circuit, if extra heat removal is required at certain points.

I use Galden 110 for a small Nd:YAG laser, and I have never gone back to water, after loosing all the H2O related hassles, and problems. As an added benifit I can now series trigger the lamp with a higher voltage. The same would be true of oil in a non optical system, where the oil does not cause problems with optical surfaces.

Water when de-ionized works great as a coolant, but keeping it that way is a lot of work and expense, not to mention the bio-slime issues. I suppose with all SS plumbing, and fluoropolymer lined tubing, then it would not be that bad. Some of the computer related water cooling stuff can represent what is close to a turn key solution for water cooling also, and save one a lot of time and parts.
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