Thursday, December 18, 2008

The Laws of Thermodynamics. . .

Internal energy U\,
Helmholtz free energy A=U-TS\,
Enthalpy H=U+PV\,
Gibbs free energy G=U+PV-TS\,
Grand potential \Phi_{G}=U-TS-\mu N\,

Today, class, we'll be discussing the laws of thermodynamics. Not really. Taking a cue from Mr. Elliott, I'll be writing about how I keep our 1100 square foot cottage warm through and through when it's in the single digits outside.

Our house has a natural gas furnace with ceiling heating ducts in all the rooms, a ceiling fan in the living room, and a woodstove insert in the master bedroom which is at the opposite end of the house from the kids' bedrooms.

The furnace works great and is controlled by a programmable, digital thermostat; unfortunately, relying on it solely to heat the house gives us a nasty shock when the gas bill comes.

The woodstove insert is the answer to that. Sommer's dad, my son Boston, and I go wood cutting in the fall and usually stock up about 2 cords of dry lodgepole pine so our heat for the winter is almost completely prepaid. (On the occasion that I don't build a fire or let it go out in the middle of the night, the furnace kicks on around 62*. Brrr.)

It took a bit of figuring out (*see tips below) how to get the most heat for the longest time out of the woodstove. Now that I have it dialed and can get a beautiful, hot, lasting fire going in no time flat, the problem is how to get the heat out of our room so we don't roast. It'll be up to 85*+ in there fast if I don't get some circulation.

I first tried putting a large fan in the doorway to pull the air out of the room. It worked but only very marginally. I then put a smaller fan in the upper corner of the door way to pull the hot air off the ceiling of the bedroom and out into the rest of the house. This worked well but looked a bit tacky.

I then realized I was working backward and hard than I had to. Instead of trying to pull the hot air out of the room, I took my big fan and put it in the doorway again, only this time I turned it around and pushed the colder air from the house into the bedroom. This immediately resulted in hot air billowing (if you could see it) out of the top of the doorway and within 15 minutes I had the bedroom cooled to a much more reasonable 74* and the rest of the house up to 72*.

I've been perfecting this system by adding in the ceiling fan on low in the living room and occasionally running just the blower on the furnace to circulate the warm air through the house even further.

The other morning it was 1* when I went to start the van, but with my wonderful fire that I had religiously kept going through the night (more like there's been a fire going for a couple weeks now) it was a toasty 73* inside.

*My tips for a great fire.
The obvious: dry wood.

Keep some air flow under your kindling.

Arrange kindling in a lincoln-log pattern. Two parallel pieces straight in with space for paper in between, two more sideways with space and so on.

Dryer lint. A small wad of dryer lint will catch a spark from a flint so well, you'll realize matches are a waste. It'll then catch your paper, too.

I've noticed when my stove is perfectly clean inside, after I've removed all the ash and charcoal, it takes a few fires to get it back to prime condition. I suspect this has to to with the retention of heat by all that ash and stuff at the bottom of the stove and I think it contributes some woodgas, too. Now if I clean out the stove, I leave a smallish layer of ash and charcoal in the bottom. Running a hot fire for days and days usually burns almost everything anyway, so my cleanings a few and far between.

Clean your chimney!!! This is a must! Every year BEFORE it gets wintry.

Clean your spark arrestor if you have one. This should be done when you clean the chimney AND after long periods of extreme cold where you dampen the fire for an extended time. Ours gets build up that starts to choke the fire and I'll notice smoke that starts coming into the room when I'm loading more wood in the stove.

(These may be specific to my woodstove and might not work for you, your results may vary. I assume no liability for any harm or injury, explosions, burnt carpet, or singed arm hair.)

Anyway, I love our woodstove and I hope everyone can use theirs to its most efficient potential!


Anonymous said...

Tinkering with house heating is nearly as much fun as tinkering with a Westy!

arwen said...

if it were legal here in the states, why... I'd marry wood heat and live the rest of my years in bliss....