LumberJocks

Kiln from and old refrigerator?

  • Advertise with us

« back to Power Tools, Hardware and Accessories forum

Forum topic by Knothead62 posted 01-09-2011 11:53 PM 5264 views 1 time favorited 18 replies Add to Favorites Watch
View Knothead62's profile

Knothead62

2364 posts in 1712 days


01-09-2011 11:53 PM

Topic tags/keywords: kiln dryer diy question tip

Bad news- our old refer in the basement went out! The good news- I can convert it to a kiln for small pieces of wood. It is about a 16 cu. ft. refer with a freezer at the top. The interior has two shelves and more can be added, if I can find some to fit the brackets. I plan on taking the compressor, etc. out and scrapping them. I figure on putting one or two light bulbs in the bottom and running a piece of metal pipe through the freezer and top as a vent. I can use the extra freezer space as storage- can’t waste valuable space! What do I need to complete the job? Should I keep the magnetic door seals?


18 replies so far

View hairy's profile

hairy

2109 posts in 2283 days


#1 posted 01-10-2011 12:27 AM

That is something I have considered, but that’s as far as it got. Here’s some links that maybe you’ve not yet seen.

http://www.woodturningonline.com/assets/turning_articles/Kiln/Introduction.html

http://www.rudieswoodwork.com/kiln.htm

-- in the confusion, I mighta grabbed the gold ...

View hairy's profile

hairy

2109 posts in 2283 days


#2 posted 01-10-2011 12:46 AM

You might want to think about leaving the compressor and refrigerant plumbing intact. There are some strict laws concerning venting refrigerant, it also can be unsafe to remove the compressor without the proper equipment.

Old refrigerator disposal is also regulated by EPA laws.

Basically, all your old refrigerator has to offer is an insulated box.

-- in the confusion, I mighta grabbed the gold ...

View Bill Davis's profile

Bill Davis

226 posts in 2675 days


#3 posted 01-10-2011 01:43 AM

An integral part of a wood dryer is air movement. IMO you need some sort of fan to keep the warm air circulating through the wood. The well insulated refridg should allow you to maintain the elevated temperature for drying. Good way to recycle the unit.

View poopiekat's profile

poopiekat

3735 posts in 2485 days


#4 posted 01-10-2011 02:11 AM

Hey, Knot,
Why not just simply convert a clothes dryer, instead?

-- Einstein: "The intuitive mind is a sacred gift, and the rational mind is a faithful servant. We have created a society that honors the servant and has forgotten the gift." I'm Poopiekat!!

View Knothead62's profile

Knothead62

2364 posts in 1712 days


#5 posted 01-10-2011 03:25 AM

PK, the dryer still works!
Hairy, I’m thinking that there is no freon since the compressor runs but no cooling in the ref or freezer. It is at least 20 years old and I’m thinking that there is a leak. I’m not going to dispose of the refer, just the non-working parts.
Bill, good idea. Need a fan at the top to pull air bottom-to-top.

View TopamaxSurvivor's profile

TopamaxSurvivor

15088 posts in 2426 days


#6 posted 01-10-2011 10:19 AM

I would use a small heater on a thermostat for the heat source. More efficient than light bulbs. Maybe a crock pot heater from the thrift store. Natural convection through the box should move enough air. If you use a fan, the heat source will not do you much good unless it comes through a heating source or the ambient temp of the intake is high enough. I doubt is the ambient temp of the basement is high enough to provide the heating????

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View Bill Davis's profile

Bill Davis

226 posts in 2675 days


#7 posted 01-10-2011 11:37 AM

Maybe a small heater and thermostat would be better but I think youy are wrong on the fan. Most everything re drying wood in a kiln is based on significant air movement. You have to bring dryer air in contact with the wood you are drying and once it has picked up the moisture from the wet wood you have to move it away or the wood will not continue to dry. Air circulation is a very important aspect of a dryer.

View TopamaxSurvivor's profile

TopamaxSurvivor

15088 posts in 2426 days


#8 posted 01-10-2011 12:14 PM

With a fan, you will definitely need a bigger heater than light bulbs or a hot plate element to keep any amount of volume heated in a lower ambient temp.

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View Bill Davis's profile

Bill Davis

226 posts in 2675 days


#9 posted 01-10-2011 12:50 PM

My dryer is about 4×4 x 8 ft and uses 6- 60 watt incandesent light bulbs. They get the heat up to a peak of about 120 deg F when all are on, Right now they are off to keep the RH at my desired level. The two fans run continuously to keep the air moving. With the heaters off it runs about 90deg. Right now I’m maintaining a RH of just under 60% to get the wood to about 11% MC. With no fans you will have a hard time removing moisture from the wood. But maybe it would be just the right conditions for your wood. If I was you I’d definitely consider a fan if I wanted dry wood.

View TopamaxSurvivor's profile

TopamaxSurvivor

15088 posts in 2426 days


#10 posted 01-10-2011 01:05 PM

What is the ambient of the area you have it in? I assume the fans are not recirculation, they are changing with outside air, eh?

-- "some old things are lovely, warm still with life ... of the forgotten men who made them." - D.H. Lawrence

View Knothead62's profile

Knothead62

2364 posts in 1712 days


#11 posted 01-10-2011 06:47 PM

Ambient temp in the garage today is 54 deg. F. This is cold as I live in SE Tennessee with 8 inches of snow today. Area has heat/AC tied in with the rest of the house. Summer time temps are mid-60’s as part of the basement/garage is underground. House is a split foyer on a sloping lot. It isn’t a big deal to plug in a heater to bring the temp up a few degrees. I’m thinking of using the fan on the compressor to draw air up out the top like a power burner set-up. I could take off the magnetic seals or rig up something to keep the door cracked.
Bill, I would think that the moist air would be drawn off the wood and taken care of by the heat pump. right now, the air is dry; static electricity is very evident. Thanks to all for their replies and advice. I’m in no hurry and will do some more research to see what fits the bill here.

View Bill Davis's profile

Bill Davis

226 posts in 2675 days


#12 posted 01-11-2011 12:36 AM

View Bill Davis's profile

Bill Davis

226 posts in 2675 days


#13 posted 01-11-2011 02:31 AM

A couple of good articles.
http://www.fpl.fs.fed.us/documnts/fpltn/fpltn-199.pdf
http://www.extension.purdue.edu/extmedia/FNR/FNR-155.pdf

Here is a quote from a good article on drying.
“Air Movement
If the air surrounding a piece of wet wood is stagnant and of small volume, it will soon become saturated and evaporation of moisture from the wood will stop. Even when there is a continuous stream of air passing over the wood the layer of air in immediate contact with the wood will move more slowly and have a higher vapour pressure than the main stream. This is known as the ‘boundary layer effect’. With increasing air velocity in the main stream this effect decreases and evaporation rates from the wood surface increase, particularly when the air flow is turbulent rather than laminar. An increase in air speed can therefore be regarded as equivalent to a reduction of the humidity barrier near the wood surfaces.

Since air passing through a stack of wet wood gives up heat and takes up moisture it is bound to be cooler and more humid where it emerges than where it enters and the drying rate is therefore slower on the air outlet than on the air inlet side of the stack. The faster the air speed and the narrower the stack, the smaller is the difference between the two sides. For this reason fairly high air speeds are desirable in a drying kiln, particularly when the timber being dried is very wet and loses its moisture readily. In most modern kilns the uniformity of drying is further improved by reversing the direction of air flow through the kiln load at regular intervals.”
(from:http://www.mtc.com.my/info/index.php?option=com_content&view=article&id=35%3Athe-theory-and-practice-of-drying&catid=31%3Atimber-drying&Itemid=46&showall=1)

View Knothead62's profile

Knothead62

2364 posts in 1712 days


#14 posted 01-11-2011 03:19 PM

Bill, excellent articles and information! Thanks. Your second post is reminiscent of the principles of convection cooking. Move the static moisture layer that is over the product and it cooks faster. I was working on my shop yesterday and ran across a fan/motor combo. I think I can rig it up at the top to pull air through the main box and out the top. I’m going to hook it up first to see if it can run continuously.

View Bill Davis's profile

Bill Davis

226 posts in 2675 days


#15 posted 01-12-2011 12:35 AM

The two fan’s I use in my dryer are the radiator fans out of a Toyota. They are made for much more extreme conditions than my kiln but will definitely withstand continuous running in a potientially moist environment. Since they are 12 Volt I’m using an old computer power supply that I had laying around. They whip up a good breeze inside. They were from a used auto parts place.

If the pieces you are going to dry start out pretty green you need to be careful and remove moisture slowly at first. Coating the end grain and/or maintaining a high RH inside will help prevent damage. Adding heat is a way to speed the drying process because it lowers the RH and the moisture evaporates faster when warm. Even with cooler internal temperatures you should keep a fan moving the air around for more uniform results. I monitor the temperature and humidity and control them the best I can without too much fancy stuff. I am using a cool inexpensive data logger help keep tabs on what’s going on though.
Also my chart ‘to live by’ in drying wood is from Hoadley’s book ‘Understanding Wood’.

If I’m starting out with pretty moist wood I start with heaters off, fans running and high RH. I gradually bring down the RH until I decide to speed up the process by adding heat. That reduces RH and accelerates drying. A key is knowing the wood’s moisture content, the temperature & RH hence the logging device. I’d rate it as a fun and productive thing to do.

showing 1 through 15 of 18 replies

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com

Latest Projects | Latest Blog Entries | Latest Forum Topics

GardenTenders.com :: gardening showcase