Microwave RIM system

This might be a simple way to implement a RIMS heater without using a direct contact heating coil.

http://picasaweb.google.com/beermeister1/BrewingIdeas/photo#5018509327335975026

The microwave could be a high output 1300 watt model, say by Panasonic, for $90. I like the fact that this one has true variable output, not on/off output. I wonder if the keep warm setting uses a temp sensor and would turn up the power as needed to keep the wort warm.

http://www.epinions.com/content_196118482564

For a 5 gallon batch with 8 pounds of grain, the mash will be 3.14 gallons at 1.25 quarts per pound. The mash weight will be about 24 pounds.

1300 watts = 4435 btu/hour = 74 btu/minute. 74 btu/minute/24 pounds = 3F/minute, which is not bad. To go from 135 to 155 would take 7 minutes at full power.

The nice things about this setup are
- its simple
- its not too expensive
- it has zero heat capacitance, meaning it instantly heats up the circulating wort and instantly stops heating it
- its a gentle heat
- it won't burn the wort, provided the recirculation rate is high enough.

Comments ?

Interesting.

I've never heard that idea before. Do you have president/reference for the idea?

Are you thinking of testing it.
I'm sure you'd be able to get an old microwave for free and test it. Even if its a lower wattage it'll brove the idea.

I'm thinking that microwave have hot spots but I'm assuming not enough to scorch the wort,. The only things I'd be concerned about is if it vaporises wort and cases oxidisation. Also I'd be concerned about microwave safety. (I don't know anything about it)

whooooaaaa, that's hot! So I'm assuming that you would run the micro's temp sensor to the MLT and use that to control the heat? Would you run the pump continuously or use a relay to control it based on micro run? This looks like a fun setup.

Co-incidentally, I was thinking about this when I replaced my microwave last week, but I have no where near the level of expertise to even think about playing around with this.

Anyone wants a free microwave to play around with, you pick up!

"Do you have president/reference for the idea?"

I thought of it at noon when making lunch. About a month ago I did a post about moving the microwave horn into the mash tun, but that seems too messy. Lately I've been active in several posts about heating elements and RIMS heaters. This just popped into my head.

I dunno if I am going to try it. I just got my mash steamer done last night. So many toys, so little time to play !

I think this would work pretty well. It would be a bit slow for doing step 10 gallon mashes, but just fine for 5 gallon mashes.

"So I'm assuming that you would run the micro's temp sensor to the MLT and use that to control the heat? Would you run the pump continuously or use a relay to control it based on micro run?"

I dunno. There are a number of ways to work it.

This is definitely not a good idea. The interior of a microwave oven is an enclosure which contains the microwave radiation. Even the window has a perforated metal mesh which prevents leakage. In order to pass the tubing into the interior, you would have to compromise the integrity of the enclosure and microwave radiation would definitely have a way out. It's not something I would ever try. The last thing I would want to find out fifteen years down the road is that I have an inoperable brain tumor because I didn't want to risk scorching my wort. Just my opinion though.

erbiumyag said:

This is definitely not a good idea. The interior of a microwave oven is an enclosure which contains the microwave radiation. Even the window has a perforated metal mesh which prevents leakage. In order to pass the tubing into the interior, you would have to compromise the integrity of the enclosure and microwave radiation would definitely have a way out. It's not something I would ever try. The last thing I would want to find out fifteen years down the road is that I have an inoperable brain tumor because I didn't want to risk scorching my wort. Just my opinion though.

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Hmmm...scorched wort or brain tumor? You've gotta have your priorities.

Whoa, whoa, whoa.... before we all get brain cancer, lets get our facts straight !

The mesh in a microwave is called a faraday cage. I'm an electrical engineer.

http://en.wikipedia.org/wiki/Faraday_cage

Microwaves are absorbed by water. As long as the hoses running into and out of the chamber have water or wort in them, there will not be any radiation. The amount of radiation due to 2 small holes would be small. One could use metal tubes as the feed through the microwave cage.

Microwave radiation does not cause brain tumors or anything else for that matter. Don't confuse microwave radiation with nuclear radiation. They are different.

http://www.ewh.ieee.org/soc/embs/comar/phone.htm

BTW: do you use a cell phone ? Do you hold it next to your brain ?

For anyone really concerned about microwave power levels, you can buy an inexpensive microwave radiation detector. Most of the microwave service shops will have them.

One could install a small piece of metal mesh into the pass through tubes as well. The mesh in the microwave faraday cage is easily porous enough to pass clean wort.

I agree that microwave radiation in the levels used in cellular communication are not going to cause brain tumors; but I'm sure two holes in a 1300W microwave are going to (or at least potentially) put out more. Yes, water will absorb microwaves, but the tubing itself will not. I can see your point if you used metal tubing to initially feed in, that would probably work, as long as you maintain flow of the wort, as you stated. My point is that microwave radiation is indeed dangerous if exposure levels are high enough and I personally wouldn't take chances in overexposing myself.

http://ewh.ieee.org/soc/embs/comar/standardsTIS.pdf

I'm not trying to rattle your cage. You might feel perfectly comfortable in trying this out because of your own knowledge; but I think that others who are less knowledgable should realize that there are definite risks, whether real or potential involved.

I'm a high power medical laser systems engineer with a degree in EE too.

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.

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 ?

brewman ! said:

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

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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.

brewman ! said:

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.

Click to expand...

This definitely sounds like a logical way to start.

brewman ! said:

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

Click to expand...

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.

brewman ! said:

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.)

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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.

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.

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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 ?

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.

"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 !

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.

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!

Just stand far enough away .

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.

david_42 said:

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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I think all of them are pretty much duty cycle 'variable' power, at least for the home consumer.

"It would have to be food-grade, high temperature AND not absorb microwaves itself."

How about a plastic similar to a bowl you would heat soup up in... in a microwave ? Lets not make this more complicated than it is.

"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!"

Lets put some numbers to things. Lets say the power radiated out of the two holes is proportional to the hole surface area divided by the total surface area of the inside of the oven. Reasonable assumption ? Actually it will probably be less than that, because the water coils will absorb a most of the energy, but lets neglect that.

I just measured a microwave and it is 13.5" x 14" x 7.5". So the interior surface area is 2 x 13.5x14 + 2 x 7.5 x 14 + 2 x 7.5 x 13.5 = 790 in^2.

The area of our 2 holes is 2 x 0.375^2 pi/4 = 0.221in^2

So estimated radiated power would be 1300 watts x 0.221/790 = 0.3632 watts.

Now that assumes that the water doesn't absorb any of the microwave power leaving those holes.

"Also, water is a dielectric and not a 'perfect conductor' the way the mesh is in the faraday cage."

I never said that water was a perfect conductor ! Here is an absorption curve for water for various wavelengths. A household microwave runs at about 2.5 GHz. Its wavelength is about 300x10^6 / 2.5x10^9 = 8 cm

http://omlc.ogi.edu/spectra/water/gif/segelstein81.gif

"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."

Do you have any math to prove this or is it just a wild guess ? Did you read all of the post and see that my approach would be to measure a few things as we went along ?

"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...)"

Yeah, the FCC police are going to shut me down for radiating less power than a cell phone !

"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!"

First of all, if you watch Mythbusters, you would find that not all metal objects arc. Secondly, if you looked at my illustration, it clearly labels the coil as PLASTIC !

"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."

And you have made that determination how ? Did you do some math or experimentation ? Are you an expert in microwave radiation ?

"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."

Otherwise known as HERMS and if you look at my sig, you will see that I have a HERMS setup now. Or one could inject steam in the mash and if you look at my other posts you will see that I am working on that too.

"I think all of them are pretty much duty cycle 'variable' power, at least for the home consumer."

Did you follow the link I provided for the microwave ? The Panasonic models are called inverter microwaves and they modulate the power level of the microwave unit, not simply turn it on and off.

Are people out to constructively contribute to this idea or shoot it down outright ? Lets keep an open mind about things and quantify the risks before we get our panties in a knot.

>>"I think all of them are pretty much duty cycle 'variable' power, at least for the home consumer."

Did you follow the link I provided for the microwave ? The Panasonic models are called inverter microwaves and they modulate the power level of the microwave unit, not simply turn it on and off. <<

No I didn't follow the link (well I did after reading this). I wasn't aware that companies had actually invested the time and money into producing a better microwave, I guess there are folks who actually cook food in them rather than reheating stuff (The only real reason to have a true variable power output vs. a duty cycle (label that ripoff))...Interesting.


>>Lets keep an open mind about things and quantify the risks before we get our panties in a knot.<<

I still say just stand far enough away

Would you still be able to pop corn in it?

Brewman,
I appologize if I came off sounding confrontational. I certainly didn't mean to offend. It is an interesting idea, I wanted to highlight some things that some people may not be aware of.
You ask if I'm a microwave expert, and I have to say, humbly, yes. I design high power components for satellite systems, and have hardware on a large number of satellites ... I'm willing to bet that the episode of mythbusters that you were watching was actually streaming through my filters...
You would actually radiate more power than you think. Your formula for surface area would be true if the microwave were lined with a microwave absorber material, which it's not. A microwave oven is a resonant cavity, and poking a hole in it couples energy out in an inductive manner - you can go to http://www.microwaves101.com/ if your interested in learning more about it, but basically, if you have the microwave - iris - freespace system 'tuned' properly, you can actually get the 'full' 1300 W coming out (ignoring the wort/water/coils that we have inside). If you don't agree, think of the openning to get the power in - the surface area of the openning is much less than the microwave oven.
No, I didn't watch the mythbusters episode, but I'm sure they probably mentioned something about the shape of the object. But what they hopefully mentioned was that depending on the shape of the object, you would get standing waves on the surface which could set up some rather large potential differences from one surface to another.

I'm busy with work things right now. I think I disagree with some of the points you make, but I'll have to check a few things before I say that.

Brewpastor said:

Would you still be able to pop corn in it?

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Shore! As long as you stand far away enough from it

In all seriousness, I admire brewman for always thinking of new ways of doing things. Engineers tend to immediately point out what is wrong with something and what the problems could be or are.

There are three engineers in a car; an electrical engineer, a chemical engineer and a Microsoft engineer carpooling together on their way to work one Monday morning. Suddenly the car just stops. They pull over to the side of the road, and the three engineers look at each other wondering what could be wrong. The electrical engineer suggests stripping down the electronics of the car and trying to trace where a fault might have occurred. The chemical engineer, not knowing much about cars, suggests that maybe the fuel is becoming emulsified and getting blocked somewhere.
Then, the Microsoft engineer, not knowing much about anything, comes up with a suggestion, "Why don't we close all the windows, get out, get back in, open the windows again, and maybe then it'll work!?"

I'm just hoping whoever tries this makes a video. Some guys on the hookah forum I frequent said they started natural coals in a microwave with great success. Others popped in and said that they tried it as well and it worked.
For giggles I decided to video tape it. Hopefully you guys get better results... no one or nothing gets hurt... and if it goes bad that at least it is funny

http://www.scalliwag.com/hookah/mwave/mwave01.wmv

*laughs. The coal video is funny. Was it actually arcing or was the coal wet and the microwave boiled the water in it and that split the coal apart ?

I love Electrical Engineers. It is easy to blame them for mechanical problems.
To follow Orfy's lead:

Good choice
Two engineering students were walking across campus when one said, "Where did you get such a great bike?"
The second engineer replied, "Well, I was walking along yesterday minding my own business when a beautiful woman rode up on this bike. She threw the bike to the ground, took off all her clothes and said, "Take what you want."
The first engineer nodded approvingly, "Good choice; the clothes probably wouldn't have fit."

Overcapacity
To the optimist, the glass is half full. To the pessimist, the glass is half empty. To the engineer, the glass is twice as big as it needs to be.

Such a waste
Three engineering students were gathered together discussing the possible designers of the human body.
One said, "It was a mechanical engineer. Just look at all the joints."
Another said, "No, it was an electrical engineer. The nervous system has many thousands of electrical connections."
The last said, "Actually it was a civil engineer. Who else would run a toxic waste pipeline through a recreational area?"

Fix it
Normal people .... believe that if it ain't broke, don't fix it.
Engineers believe that if it ain't broke, it doesn't have enough features yet.

At a party, how can you tell the difference between an introvert engineer, and an extrovert engineer?
The extrovert engineer is looking down at the other peoples shoes...

Ha, ha... you guys make fun of engineers until you need one !

Microwave leakage detectors.

$29 http://www.comforthouse.com/micleakdetwi.html

$50, $43
http://www.emsdiasum.com/microscopy/products/equipment/accessories.aspx
http://www.technika.com/Sper/s840024.htm

$30
http://www.inspectiondepot.com/Catalog/product_detail.php?PID=156

Here is a document that explains the leaks themselves and the effects.
http://www.ccohs.ca/oshanswers/phys_agents/microwave_ovens.html

brewman ! said:

*laughs. The coal video is funny. Was it actually arcing or was the coal wet and the microwave boiled the water in it and that split the coal apart ?

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I'm not real sure. The coal was not wet. But I guess there were pockets with just enough moisture to to heat and rapidly build pressure to cause the little mini-explosions.
The guys on the hookah forum still laugh about that video.

As far as this microwave idea you guys are throwing around, is anyone here going to give this a try and see if it works? I have an old microwave. I may look into it.

I am going to try it, but it might take me a while until I do. I am swamped with work and family at the moment.

brewman ! said:

Ha, ha... you guys make fun of engineers until you need one !

Click to expand...

'sokay I'm allowed to make fun of myself

It is a interesting idea. Controlling the temp increase could be challenging, but that is why I love this hobby.

Wonder if the microwaves would harm the surgars and other goodies you want in the wort? I am a mechanical guy, so maybe a chemical guy could chime in.

Brewman,

I admire your inginuity but I am missing something that may have been earlier in the thread, but if it was I've missed it. My question is, why would you want to take this route rather than a more conventional RIMS or HERMS?

Of course, there's always the answer, "I want to do it to see if it can be done" and if that's the case then that's great. I'm just curious.

/Phil.

Well, if I attempt this it will really be a preheater for my boils. After reading the thread on using the tankless water heater this sounds like a viable alternative the that.
Does that sound like a good idea to you guys? Then again, the guys on the hookah forum thought the charcoal in the microwave was a great idea.

The microwave RIMS experiment went tragically wrong!