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hot water heating sstem question

I heat my home entirely with a wood stove which I built out of a 55 gallon drum. Standing behind the stove until just recently was a forty two gallon dull color flat grey (just plain old) galvanized water tank.

As cold water flows into the bottom of this tank and sits awhile, it is pre heated by the stove. Then when hot water is called for this preheated water flows out of the top of the tank into the nearby electric hot water heater . This scheme which has been in place for the past 15 years has saved us a substantial amount of money.

Recently this tank had some spots that were rusting through and I replaced it with one of the same make and model. The new tank sits behind the stove just as the old one did and although it's already been quite cold here in N ew Hampshire and the stove's been running fairly hot the water doesn't seem to get as hot as it did before.

The only thing that's different is that the old tank was a flat galvanized metal and the new tank, although also galvanized is a shiny silver exterior . Could the shiny finish be reflecting the heat from the stove instead of a bsorbing it. This really has me puzzled. Thanks for any advice. Lenny

Reply to
captainvideo462009
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It could be. Shiney things reflect the heat and darker colors sbsorbe the heat. It also works in reverse. A shiney outside will keep cool longer and a dark object looses heat faster.

Try giving the tank a coat of black or dark color paint.

Reply to
Ralph Mowery

Black paint on the side facing the stove is the most important, but even on the back side it will absorb heat from the room itself if painted black. This assumes that incoming water is colder than room temperature. Have you thought of running a coil/loop or two of copper tubing thru the bottom of the stove to get additional preheating?

Reply to
hrhofmann

Quoting Ken Mellendorf :

There are three basic methods for transferring heat from one object to another: conduction, convection, radiation. Conduction is the method we are most familiar with. Conduction is a hot object touching a cold object. Convection is moving liquids and gases carrying heat from one location to another. An example of this is air circulating through ducts and vents. Neither of these has anything to do with color.

Radiation is radio waves, microwaves, light waves , x-rays, etc. carrying heat energy from one surface to another. Visible light depends on color. In the dark, there is no visible light. Infrared light is the most common heat transfer radiation in the dark. Some material can easily absorb infrared radiation, and some cannot. Again, it is not based on color.

What does affect it is "shininess". A shiny surface is very smooth. It is easier for any radiation to reflect from a smooth surface. Shiny metallic surfaces tend to be smoothest and best reflective. This is not due to color: a smooth metallic surface has no little grooves or holes in which to trap extra waves. Color as we define it only relates to visible light.

Reply to
philo 

Agree 100% with the advice to paint the tank flat black.

I don't agree that a matte black surface has little grooves or holes in which to "trap" electromagnetic waves. I would agree that a matte black surface has higher "absorbtivity" than a gloss black surface. Just as different surfaces EMIT heat differently, different surfaces absorb heat differently, and the best absorbtivity is generally with the surface that reflects the least amount of light, and that would be a flat black surface rather than a glossy black surface.

Still, the fix is the same. Paint the tank with the flatest blackest paint you can find. Make it look like a black hole.

Reply to
nestork

On Wednesday, December 3, 2014 11:24:20 PM UTC-5, snipped-for-privacy@gmail.com wr ote:

n drum. Standing behind the stove until just recently was a forty two gallo n dull color flat grey (just plain old) galvanized water tank.

reheated by the stove. Then when hot water is called for this preheated wat er flows out of the top of the tank into the nearby electric hot water heat er. This scheme which has been in place for the past 15 years has saved us a substantial amount of money.

d it with one of the same make and model. The new tank sits behind the stov e just as the old one did and although it's already been quite cold here in New

to get as hot as it did before.

d metal and the new tank, although also galvanized is a shiny silver exteri or. Could the shiny finish be reflecting the heat from the stove instead of absorbing it. This really has me puzzled. Thanks for any advice. Lenny

Thanks guys. I kind of thought the same. Problem is though this will have t o wait now until the Spring. My wife is very sensitive to the fumes so I wo n't be able to do any painting down there this Winter. I was thinking that I would have to use a very high temperature paint. Perhaps something like a n engine paint, but that would only come as a high glossy type. Does anyone have any ideas for a high temperature flat paint? Lenny

Reply to
captainvideo462009

I've heard of Bar-b-Que paint, but I've never used it.

In radiant heat transfer, surfaces that are good emitters of radiant energy also tend to be good absorbers of radiant energy, so it would seem to me that someone would be selling a flat black paint for headers for engine exhaust systems. Headers get very hot, and if I were going to design a pair of headers, I'd paint them flat black to radiate as much heat as possible from their surface. I expect if you look for header paint, you should find a flat black high temperature paint that has good emissivity and absorbtivity characteristics. Or, at least, that's what I'd focus on rather than Bar-B-Que paint where the appearance of the Bar-B-Que is a more important factor in chosing the colour and gloss of the paint.

Reply to
nestork

Once again, Google is your friend:

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Reply to
trader_4

How hot does it get? I doubt you need a very high temperature. To eliminate the fumes and do it now, I'd use a latex. With water, the temperature will never get above 212

Another option is to get a can of black spray for bbq grills. It is flat black and will take all the heat it will ever see.

Reply to
Ed Pawlowski

On Wednesday, December 3, 2014 11:24:20 PM UTC-5, snipped-for-privacy@gmail.com wr ote:

n drum. Standing behind the stove until just recently was a forty two gallo n dull color flat grey (just plain old) galvanized water tank.

reheated by the stove. Then when hot water is called for this preheated wat er flows out of the top of the tank into the nearby electric hot water heat er. This scheme which has been in place for the past 15 years has saved us a substantial amount of money.

d it with one of the same make and model. The new tank sits behind the stov e just as the old one did and although it's already been quite cold here in New

to get as hot as it did before.

d metal and the new tank, although also galvanized is a shiny silver exteri or. Could the shiny finish be reflecting the heat from the stove instead of absorbing it. This really has me puzzled. Thanks for any advice. Lenny

Thanks so much for all the great information and advice. I really do apprec iate it. Lenny

Reply to
captainvideo462009

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