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  • liquid insulator

    I had a couple questions, but this is the only one I can remember right now. Is there such a thing as a liquid insulator? Maybe it would be a liquid of sorts that's filled with microbubbles of something- this is just academic at this point, but I do have an application if it passes the mental design stage.

    Ideally, the carrier liquid would be much lighter than water, and the microbubbles would maintain their affinity to the carrier liquid, in other words, wouldn't separate and join with the water.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    3M makes a wide variety or ceramic and glass bubbles. These are often used in making something like man-made tile or concrete more insulating.

    Does the insulator need to stay liquid or does it just need the liquidity to get to where it is going?

    Off the top of my head, 3M glass bubbles mixed into some type of silicone engineered fluid from Dow Corning sounds like what you might want. Whether it insulates well is another question although without knowing what you're trying to do, it's difficult to say anything rational.

    --Cameron

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    • #3
      Hydraulic oils are often highly dielectric (when new), even PURE water is. Imperial Oil's Univist N22 is one I know is definitely highly dielectric, since it is used in the bucket trucks hydraulic systems that we use when we do rubber glove work on 25KV and barehand work on 240KV energized power lines.
      Location: Saskatoon, Saskatchewan, Canada

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      • #4
        It depends a lot on how good an insulation material you need for your application.

        Its hard to imagine a liquid system, assuming you can make one with long term stability, that comes anywhere near the insulation values of the standard board foams, ie polyurethane or polystyrene foam.

        You can get around that if you can make the insulation a lot thicker to counteract the lower insulation value.

        What sort of hot/cold temperatures are you thinking of?

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        • #5
          Yea as the previous posts have shown. Do you want an electrical or
          thermal insulator? Or for that mater there are several other things
          that could be "insulated".
          ...lew...

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          • #6
            I can't imagine a fluid making a good thermal insulator. Maybe for something interesting (plasma inlet on a supersonic centrifuge?), but in general use, you would wind up with convection currents that would transport heat better than insulating it. That is also why they don't make double pane windows 4" thick. Air starts convection in 0.5"-1" spaces with very little effort. As far as a liquid, you would also have containment concerns when looking at longterm use.

            As far as fluid making a good electrical insulator, there are tons of examples. Coolant in line transformers comes to mind first...

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            • #7
              An electrical insulator is easy - pcb's, mineral oil, silicon based oils, etc. Of course these all conduct heat well which is why they fill transformers

              Heat insulators... thats much more difficult because even if the material doesn't usually conduct heat it will due to convection. You thermally excite one atom and (since its not bound very tightly) it bumps into another atom and so on conducting the thermal energy fairly well.

              <edit> oh just saw the previous post... what he said

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              • #8
                Most transformers are being filled with vegetable oil now. Far fewer hassles if it leaks.
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  vegetable oil? now thats an interesting one ...

                  all of the transformers owned by com-ed are still mineral oil.

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                  • #10
                    World's first vegetable oil filled transformer at 132,000 volts

                    13 Sep 2006
                    EDF Energy Networks will be trialling the world’s first major transformer filled with vegetable oil in a cutting edge development for the electricity industry.

                    The insulating liquid, made from edible seeds, will replace the use of mineral oil in a 132,000 volt transformer serving thousands of customers in Luton.

                    Made from a natural, renewable resource the fluid is an environmentally friendly alternative to depleting mineral oils. The green liquid is also biodegradable, less flammable and is reputed to extend the life of the transformer.
                    http://www.edfenergy.com/html/showPa.../20060913.html

                    They are switching as fast as they can because it eliminates toxic waste concerns and potential lawsuits when leaks happen.
                    Free software for calculating bolt circles and similar: Click Here

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                    • #11
                      Biodegradeable, eh.......? Maybe like the insulation on some european cars? That started to biodegrade a little early...........

                      Most veggie oils will oxidize/degrade at lower temps and in less time than mineral oils, and may become somewhat conductive if they do.

                      Well, presumably they know what they are doing..... better than the Soviet experiment of saving power by running at lower voltages........ motors didn't like it very much.
                      1601

                      Keep eye on ball.
                      Hashim Khan

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                      • #12
                        Without divulging more than I should about this- the application is for heat insulation, not electrical- I should have realized to mention this. The space it has to occupy is about two inches thick, so we're thinking air might convect too much and transfer heat across this gap. We were hoping that an insulating fluid would give better insulation value in this case. Water will at times displace this fluid to actually conduct the heat when required. That's all I can say about this.

                        As far as electrical insulation, I like the vegetable oil in the transformer idea. They should put shredded potatoes in with it. Then if it overheats, the hydro guys will have something to snack on while they work on it.
                        I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

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                        • #13
                          You will have a bit of a problem with this as air has about the lowest conductivity as seen by most heat insulation materials the active ingrediant is air you can find a list at http://www.engineeringtoolbox.com/th...ity-d_429.html
                          You may be better off if you could get a vacuum section around the object that is the best although will suffer from radiation heat losses.

                          Peter
                          I have tools I don't know how to use!!

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                          • #14
                            I don't think you will find a solution where the liquid is less dense than water. However, Fluorinert FC-72 has a latent heat of vaporization of 88 j/gram whereas water is 2260 j/gram. This implies that as long as it is kept under pressure to prevent the vapor phase forming it has a very low capacity to transfer heat. It is virtually insoluble in water, <5 ppm, and environmentally friendly. It is however much denser than water at 1.68.
                            Free software for calculating bolt circles and similar: Click Here

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                            • #15
                              Originally posted by darryl
                              The space it has to occupy is about two inches thick, so we're thinking air might convect too much and transfer heat across this gap. We were hoping that an insulating fluid would give better insulation value in this case. Water will at times displace this fluid to actually conduct the heat when required.
                              Two thoughts on improving the insulation value of a 2" air gap and still allow cooling water to flow through the void when required

                              Multiple layers of aluminium foil with a .5" air gap in between them make a very efficient thermal insulation, getting towards EPS values. This assumes of course that we are dealing with flat panels.

                              For irregular shapes, a coarse open cell foam of the type used in race car fuel tanks, installed in the 2" void would reduce convection losses and allow water flow.

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