need advice on pikie heating system

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  #1  
Old 01-02-05, 07:54 PM
B.F.I.
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need advice on pikie heating system

im tryin to heat a space thats 10m cubed 4 inches of fibre glass insulation all around it covered in hard board, to 80 degrees C. also i have 4 11mm plywood shelves

At the moment im using a 2.3kw kitchen fan heated oven without the door, without the shelves ive managed to get to 40C, and with them, 20 - 30.

Does anyone have ne ideas on how i could improve it, i have no xtra cash so i have to make this work as it is, also i cant draw much more power if any.

how much would it improve if it was lined with tin foil?

and is there anything technical i should know or be thinking about.

thx
 
  #2  
Old 01-02-05, 08:30 PM
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I'm not going to ask... The first thing that pops into my head is gasoline... Sorry... I know this is a serious problem for you, but honestly you're probably asking the impossible and definitely the impractical.

Convection, conduction and radiation are the 3 forms of heat transfer. Given your scenario, convection is probably your biggest enemy with conduction following closely behind. Increase insulation (another 4 inches?) to decrease loss via conduction and seal air leakage (caulking) to decrease loss via convection. Tin foil would decrease radiation which is the least of your worries. Any chance you can make the space smaller?

Is the oven cycling on and off? Have you tried running it on a self clean cycle . Sorry, kidding again. Be patient, as soon as that oven burns up, you should surpass your goal. Do you have insurance?

Doug M.
 
  #3  
Old 01-02-05, 08:57 PM
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lol the building its in is made of asbestos lol so haha. what u mentioned about tin foil/radiation being least of my worries, that mean that it wont do much good?

the shelves seperate the space into 5 40cm high 2m squared spaces, however the oven is at the bottom so we have holes in the shelves to try n let heat get about, more insulation is unlikely altho could probably pikie something.

one other thing some of the wood is damp, does that mean that it will require heat energy to dry them out before it will get hotter?

other than this, u know of ne other cost effective ways to heat the space to atleast 50C but 80C would be nice.
 
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Old 01-02-05, 09:21 PM
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Asbestos?? You're kidding right? Foil probably wouldn't help but it wouldn't hurt.

If the wood is damp, it will require energy to dry it out. It will hold the temp down a little until it gets dry, but that moisture has to go somewhere. Maybe you should add some airflow until everything gets dry.

I'm a little low on ideas. Could you add a wood stove? Portable kerosene heater?

Doug M.
 
  #5  
Old 01-02-05, 09:47 PM
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lol yeah the actually building is asbestos but i constructed a wooden box which is what im heating, im still experimenting with heating methods but i dont think i can use more than 3 - 3.5kw, i got a couple of fan heaters but they limit themselvs to 30 C which is no good, i had a look at some others but details were fairly vague and prices steep, maybe u could suggest something?

thx for the help
 
  #6  
Old 01-02-05, 10:12 PM
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What's really vague here is the details about what you are trying to do.

A simpler but detailed explanation might help.

What environment this "thing" is located in and what exactly are you trying to heat.
You say heat but are you trying to, dry something and if so, what is it.
What you are working with will be just as much a heating load as the walls of your building.

Also when you say ten meters cubed do you mean 10 x 10 x10 meters or 10 cu meters.
 
  #7  
Old 01-02-05, 10:52 PM
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i guess i actually meant 2.2 x 2.2 x 2.2

basically this space needs to be between 50 and 80 degrees C to allow carbon fibre to cure. thats all
 
  #8  
Old 01-03-05, 06:57 AM
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Hmm!

If right now you are throwing 2.3 kw into this space and if it can't get the temp up to 40 degC ( around 104 degF) something is taking the heat away.
If this much heat was in the space you describe with out any outside influences, the temp would go up.
Sounds like maybe you have too much moisture in there and maybe not enough ventilation and air change to keep the humidity down.

If you are able to provide 30 amps at 220 volts, a portable electric construction heater could do it if the moisture was somehow controlled.
If done safely, you could replace the internal thermostat with a commercial control that is more in the range you need.

Take some pics and have them hosted somewhere.
Still too many unanswered questions about this.
 
  #9  
Old 01-03-05, 06:04 PM
B.F.I.
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http://www.geocities.com/kjwqd/HR_prof.JPG
http://www.geocities.com/kjwqd/inside.JPG
http://www.geocities.com/kjwqd/inside3.JPG
http://www.geocities.com/kjwqd/oven_front.jpg

there thats it, not sure what all the little dots are coz its not the camera, probably asbestos in the air lol.
 
  #10  
Old 01-03-05, 07:24 PM
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Now I see!

Firstly, a big problem is the shelving.
You would need much more open shelving in order to have decent circulation.
Either that or a fairly high cfm fan to move the air around.

What I suggest you do is remove the shelving and see if the oven can maintain the space at the temp you want.
Then add what you want to heat up and see if the kw you have in there is enough.

Another problem is that an oven control doesn't usually go as low as you want.
150 degF is usually the lowest setting you can get with a standard oven control, you need 104 degF.

As a rough guess I would say with a load you would possibly need no less than 4 kw which would require 30 amps at 240 volts.
 
 

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