Erbium:YAG

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Before there are any bad feelings, I do want to give merit to your idea Brewman. Even though my own expertise in the electromagnetic spectrum is from UV to Far IR, I'm just plugging away as if I were in a design review meeting and throwing out my own observations. Naturally if safety can be maintained, which we know is the first priority in any design, I say go for it. It wasn't my intention in my original post to try and make you look stupid; so I'm sorry if it might have come across that way.

brewman !

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erbiumyag, no harm, no foul. You are right that something should have been mentioned.

As far as safety goes, I would not be terribly concerned about hurting myself. As far as EMI emissions goes, I think this needs to be looked at.

Care to help me brainstorm together on possible solutions ?

My approach would probably be to find a junker uwave, drill the holes, sneak a microwave detector and measure the leakage worst case - no water, open holes, no load. Then go from there.

Then start improvising shielding. Something as simple as wrapping the hoses with grounded tinfoil for 6" might do the job ?

What about using 2 pieces (one for each hose) of copper pipe in an upside down U shape, grounding them to the cage. My thinking with this is that even if the tubes were empty, the waves would have to enter the tube from the bottom, go around the curve and exit out the bottom again. The whole tube would be grounded so they should be absorbed anytime they touch the tube, right ? Or will they reflect ? And if the tubes were full of wort, then the leakage would pretty much be zero as far as I can tell. (The wort would absorb the uwave energy.)

Do I have this right ? Do you have any other ideas ?

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Erbium:YAG

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I'm glad to hear it. The last thing I'm trying to do on this forum is piss people off.

This definitely sounds like a logical way to start.


One better - Why not cover the entire length of tubing with a double layer of stainless or copper braided shielding and then ground it to the faraday cage.

This might not be necessary if the braiding does the job.

My only other suggestion would be to test out, or at least research various types of tubing to see which will probably hold up the longest after constant exposure to microwaves.

brewman !

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Thats a great idea, especially since all the HBers know where to get stainless braid for the mash tuns. A few feet would do it.

uwaves travel on the skin effect at that frequency and braid has a terrible skin, and yet its a conductor. Should kill any emission immediately.

So who is going to stink up their microwave cooking water in a plastic hoses ? Volunteers ? Err... anyone not married here ?

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Bsquared

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I'm no engineer but I have a degree in molecular biology/ biochemistry. I can tell you this that Microwaves heat water buy causing the bonds between the Oxygen and the Hydrogen atoms to vibrate giving the water molecule energy causing it to move rapidly, and like brewman said there are no radioactive partials emitted form a microwave. you don't want to get too close to microwave radiation because you are 90% water and stray microwaves can cook you...

on that note, if you drilled holes in the plexiglass and had a 50ft coil of high temp tubing running through it you could pump the wort through that while the microwave is running. personally I think it sounds like a cool Idea.

brewman !

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"just smacks of a Rube Goldberg machine to me."

Exactly the opposite for me. Its simpler than a regular RIMS or HERMS setup. Want to raise the temp of the mash ? Set the microwave to high for 7 minutes and turn on the pump. You don't have to stir the HLT or monitor its temp like you would with a HERMS and you don't have to worry about wort burning like you do with RIMS.

I think it would be pretty slick. Slicker than the mash steamer ? I dunno. I'll answer that after I build both !

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Tom Smith

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While we are throwing credentials out there, I as well am a electrical engineer, and have been working with microwave communication equipment for many years, and just recently took on a new role as radiation engineer to analysis circuits in a nuclear radiation environment.
So ... there is a difference between nuclear radiation and microwave radiation, and that does not mean that microwave radiation is safe! Sure the debate is out there regarding cell phones, but don't forget that cell phone only transmit a few watts of power versus the 1300W of power in your oven!

Also, water is a dielectric and not a 'perfect conductor' the way the mesh is in the faraday cage. If you poke a couple of holes in your microwave oven, and 'fill' the holes with water, you attenuate the leakage, sure, but you are still going to have lots of leakage, and at that power level there can be health impacts over a period of time. And even if someone wants to debate the health impacts, the faraday cage is also there to keep the emissions below FCC requirements, so if you increase the emmisions you are actually breaking government regulations (the requirement is international...)

If you put a metal coil inside the microwave oven, you will get some REALLY high potential (voltage) differences at various points around your setup, and you will have a REALLY cool light show due to all the breakdown and arcing. Remember what your mom always told you - don't put anything metal in the microwave!

I do honestly enjoy and respect the ingenuity homebrewers show, but sometimes creativity can be dangerous. This is a really clever setup, but it is not worth the risk. You'd be better off running a coil through a pot of hot/boiling water on a hot plate and controlling the heat that way.

Tom Smith

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If you did want to stick with the microwave idea, you could use microwave safe plastic tubing (off hand I really can't think of what to suggest), drill a series of small holes through the door, where the holes in the mesh already exist. If you could find a good way to seal the tubing to the door you could actually pass the water through the small holes. The only thing to caution you on with this is that water actually makes things look 'bigger' to microwave radiation because it is a dielectric and has a dielectric constant higher than air, and so the holes in the mesh that you are pumping water through would actually appear to be bigger to the microwave power, and therefore you'd actually increase the leakage power. But then that will be offset by the amount of power absorbed by the water, and I'm only guessing here but I imagine the absorbtion due to the water will be higher than the increased leakage. So the net impact would probably the an overall reduction in leakage. Something worth testing!

zoebisch01

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Just stand far enough away .

david_42

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My question would be: What kind of tubing are you thinking of using? It would have to be food-grade, high temperature AND not absorb microwaves itself. The latter so the energy is going into the wort and not the tubing. Any hydrocarbon-based tubing would be out of the question. Maybe a medical-grade silicon designed for autoclaving?

I'd look for tubing first.

Second point: Is the oven you are thinking of using variable power or does it just cycle on-off? There are very few ovens out there that actually vary power levels, as it is an expensive process.

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