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Old 01-10-2007, 08:27 PM   #1
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Default 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 ?

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Old 01-10-2007, 08:47 PM   #2
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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)

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Old 01-10-2007, 08:47 PM   #3
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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.

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Old 01-10-2007, 08:53 PM   #4
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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!

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Old 01-10-2007, 08:59 PM   #5
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"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.

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Old 01-10-2007, 09:20 PM   #6
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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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Old 01-10-2007, 09:26 PM   #7
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Quote:
Originally Posted by erbiumyag
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.
Hmmm...scorched wort or brain tumor? You've gotta have your priorities.
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Old 01-10-2007, 09:29 PM   #8
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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.

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Old 01-10-2007, 09:55 PM   #9
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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.

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Old 01-10-2007, 10:19 PM   #10
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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.

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