Homemade Pellet Water Heater

[mepellet]

ok non expert is a btu a btu in your most humble opinion

A btu is a btu yes.

The definition is something like..... the amount of energy required to increase the temperature of 1 pound of water by 1 deg F.

 

[mepellet]

Mepellet is pretty good with #'s.....

Im not gonna say what he did for me, but it was free and it took him some time..

There are some people here that are good at this stuff... Mepellet is one good with #'s. IMHO

Im no expert either. But a BTU is a BTU. Whether is Pellet, Gas, Oil, Etc... Dont know why it would be different? ?

I am by no means an expert and don't claim to be but not only do I enjoy looking and thinking about these types of things but I also enjoy being able to help a couple of fellow forum members out. Especially since I have learned so much from here about pellet stoves. Looking into upgrading our old wood stove in the next few years so I am sure I will be turning to the wood burning forum then.

 

[woodgeek]

Um, if the material leaving is char (carbon) and not ash, then you have incomplete combustion and less than 8000 BTU/dry pound input. Math is easy and measuring is hard. Measurement error? Are you measuring the water flow volumetrically at the same time the unit is running, or relying on a flow meter (which are notoriously inaccurate)??

 

[mepellet]

Numbers seem to be pretty close:

1gpm x 8.5lbs x 60 min/hr = 510 lbs water / hr

510lbs water x 45F delta T = 22,950 btu

You say 3.15lbs x 8000btu = 25,200 btu input

Finally 22,950 btu out / 25,200 btu in =~ 91.1% efficient "apparently"

I throw the "apparently" in there because several things can affect this calculation. What types of actual temps are we talking? What is the initial temp of the water? What is the final temp? .

Very good points. The weight of a gallon of water does depend on temperature. I commonly use 8.34 pounds per gallon which I believe is at 60 deg. F.

What is the ambient temp while the run is happening? We are talking 1gpm of 'new' water for the whole period...'cause circulating 10 gallons of water at 1gpm changes things substantially! Is there electrical input for pumps, augers, conveyers, blowers, etc.For instance, I could draw a 55 gallon drum of well water at 60F, leave it to sit in the afternoon sun with a small candle beside it and come back to find it's 105F in the afternoon. I find the amount of candle burned is a few hundred btu and the water has increased by thousands of btu. So did I get 1000% efficiency from that candle? Well, no, not really - heat snuck into the system from sources which weren't considered in the original equation... the sun! A super efficient water heater in the summer is not hard...on a -10F winter day...considerably more challenging.

When the OP says an increase of 45 degrees I assume he means that water coming into the heating device is 45 degrees lower than the water coming out. So he either must be dumping 1 gpm out of the system or losing the 45 deg F out in a heat dump zone. True about the electrical requirements. I was only looking at the combustion efficiency.

Likewise if this is a circulating system...you can only consider the weight of water in circulation, not the actual gallons of flow. Say I have a 100 gallon tank and a 100GPM pump and the heat goes up by some amount in an hour...I can only consider the 100 gallons or 850 pounds, not 100gpm x 8.5lbs per gallon x 60 minutes = 51,000 lbs. Further, relatively large pumps on relatively small volumes can add a notable amount of heat. I have a hot tub heated only by the 7hp jet pump...1hp is about 2550 btu - so if this heat is fully captured, it can add to the total considerably.

I think you need to consider the 51,000 lbs when calculating btuh. You need to get the gallons per MINUTE to gallons per HOUR. Otherwise your units would be off. Yes you can say 1hp equals 2550 (1hp = 750w & 1w = 3.4 btus) but most of that energy goes to moving the water. It's like when you use a large fan in an air handling unit. You don't count 100% of the fan's hp in system heat gain. Only a very small fraction...

On the 'plus' side, technically you should consider the heating of any storage tank, piping, water pumps, hoses, etc. Those all have thermal mass and are being warmed by the heater as well.

Very good point. This will be a hard item to put a real number on.

Modern 95% efficient boilers can be had...so efficiency of this level is not out of the question, but they need a clean burn and actually condense the water out of the flue gas to recover that extra bit of steam energy. Of course, heat pump water heaters can approach a 'coefficient of performance' (COP) of 2.5 or better...which is 2.5 btu out for 1 in, or an apparent efficiency of 250%.

One concern - you mention a lot of charcoal being produced in this system? Charcoal is carbon and carbon is energy, so if the charcoal is piling up in huge amounts a lot of energy is going with it. You also show a pipe with steam coming out? Heated water or wood exhaust? If this is wood exhaust, that steam itself has recoverable energy when it condenses, so again piping away more energy.

 

[mepellet]

measuring is hard. Measurement error? Are you measuring the water flow volumetrically at the same time the unit is running, or relying on a flow meter (which are notoriously inaccurate)??

How true it is.

 

[homemade]

How true it is.

5 qt ice cream pail in a minute 15 seconds
water is flow out of well at 57 degrees and rising 45 degrees and dumping on ground don't have city water as you see

 

[woodgeek]

can't argue with a well-calibrated pail.

 

[Corey]

Just don't tell me the temperature was measured with a bungee cord, a piece of bailing wire and two twigs from a willow tree!

 

[homemade]

willow tree with a crook in it na that is how you find water

 

[homemade]

willow tree with a crook in it na that is how you find water

at least that is how my uncle thought he could find it, water witching, impressive to watch

 

[homemade]

Just don't tell me the temperature was measured with a bungee cord, a piece of bailing wire and two twigs from a willow tree!

na a ranco temp controller

 

[homemade]

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[homemade]

then i find out water weight per gal changes at different temps for instance
68 water =8.33 lbs
104 water =8.28 lbs
140 water = 8.2 1lbs
176 water=8.14 lbs

 

[mepellet]

then i find out water weight per gal changes at different temps for instance
68 water =8.33 lbs
104 water =8.28 lbs
140 water = 8.2 1lbs
176 water=8.14 lbs

Yes, I alluded to this in a previous post above...

 

[homemade]

well I just signed letter for a patent attorney wish me luck

 

[Realstone]

Keep us posted (at least as far as is prudent regarding public disclosure that is)

 

[maple1]

You come up with a ultra-high efficiency wood fired water heater, I'll drive out there and help you test it! That's something I'm yearning for......something you can chuck three or four splits in per day and keep a good supply of hot water, that's what I want......

Sounds like you need a gasifying boiler.

 

[homemade]

still looking for someone to help perfect this thing and maybe one day get it insulated, right now I been running it for last three weeks or so, whenever the cold started and using about 2 five gal pails a day heating 2 car garage and old farm house