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Brad White_185

is a kind of surgery we do here in Massachusetts by the way. Everywhere else it goes like this:

Change of State of ice to water or water to ice is 144 BTU's per pound.

Here is some trivia behind it:

Take one ton of ice, (2000 lbs.) and melt it over a 24 hour period. If each pound absorbs 144 BTU's, the total amount of heat to be absorbed is (2,000 x 144) or 288,000 BTUH.

If over a 24-hour period, that 288,000/24 = 12,000 BTU's per hour.

That is the origin (and definition) of "one ton of cooling", all based on the rate of a ton of ice melting over a 24 hour day expressed on an hourly basis.

To change water to steam (at sea level atmospheric pressure of 14.696 PSIA from and at 212 degrees F.) takes 970.3 BTU's as Devan said.

Steve Ebels_3

Regarding phase change...............

How many BTU's does it take to turn 32* ice into 32* water and how many BTU's does it take to turn 212* water into 212* steam?

I'm trying to explain the loss of efficiency involved in burning unseasoned wood to a person who is rather dubious about what I am telling him.

bruce_21

ice to water 80 cal/gm, water to steam 539 cal/ gm. Check out all the details at http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/phase.html

D. McLean

If my memory

Serves me correctly, a British Thermal Unit BTU is the amoount of heat required to raise one pound of water one degree F.

WV EGBERT_2

Quantity?

But let's say one pound of water.

It takes approx 180 btu's to raise 32* water to boiling 212* water.
At 212* to steam would take an additional 970 btus, for one pound of water.

Not sure about latent phase change of water to ice, but I would think it is easier to add heat to a substance, rather than trying to pull it out.

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Steve Ebels_3

Here's the scenario

This guy currently has a typical outdoor wood "boiler". He buys his wood in July or August by the pulp cord and literally cuts it into 20" chunks as he needs it through the winter. The moisture content is 35% and up according to my meter. This moisture has to be evaporated to a certain point before combustion can take place. He's basically throwing frozen pieces of wood into his "boiler", expending huge amounts of heat just to phase change the moisture/ice in the wood to water and then finally to steam which will evaporate allowing the wood to actually burn.
I'm attempting to put a number in front of him that he can grasp so he can see why he's burning 16 pulp cords a year to heat 1,800 sq ft.

WV EGBERT_2

A typical outdoor wood boiler

is about 40% efficient. ( just a guess, but I doubt too much higher)

So about 7 of those cords are useful and the remaining is warming up the clouds.

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bruce_21

He should definitely be buying his wood wayyy in advance and letting the sun do some of his work for him

Weezbo

Steve tell him to find...

pallets from some glass company or shipping company..most likely it will be seasoned wood ... cutting splitting stacking and drying wood uses a variety of tools and skill sets.. perhaps it would be like describing a deer to someone who just went out to the country and shot the farmers cow because it was brown with horns ... and Hey you told him that the brown gizmoes with 4 legs and horns were deer

the more you say the less he will understand...ask him if he has ever seen a cord of wood prior to his experience with the boiler. ask him if he figures they make splitters and driving wedges for any particular reason...most people season it a year split and stacked..and often those are logs that have been stacked to dry the season earlier. right now a cord is 200$ here..the only good thing about it is it has only doubled in price...

BTW one of the young contractors burned 4 cords in his home last year and had his viessmann drinking all of 200 gallons in three months..and his home is over 1800 Sq ft...well insulated and sealed with radiant heat..the fireplace is more of an "atmosphere" he and his wife happen to like



Namaste *~/:)

EMB

Way cool!

Great explanation Brad

Glen

brain freeze!

and .5 btu per pound to raise ice from 0 F to 32 F solid.

Mitch_4

its

144 ice to water, 970 water to steam