How do water heaters work?

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Hi,
I would like to learn how the water flows in a hot water heater. Is there a description somewhere on the web. I'm thinking of an old fashioned cast iron radiator or a modern runtal, such as this one:
http://www.eqwip.com/images/upload/items/solea.jpg
I'm basically puzzled how the water enters on the bottom left, leaves on the bottom right and at the same is able to reach the top.
Thanks
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It's heat transfer and not irrigation. The water will give up it's heat wherever it can.
R
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Aaron Fude wrote:

Heat rises?
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On Sat, 14 Feb 2009 21:07:09 -0800, Aaron Fude wrote:

Are you asking about whole home heating using a hot water boiler using an electric circulating pump with piping for 180 degree (F) water and cold water return?
Are you asking about a whole home heat system that uses a boiler with steam heat and gravity cold water return to the boiler during "off" cycle of the steam heat?
Your link looks like it could just be using potable (drinking) hot faucet water to warm the towels. The hot water for your shower passes through the towel warmer warming your towels (and cooling your shower water.) It is just plumbing water in, water out. Complex "S" pattern of piping makes the device circulate the water (water pressure and flow from city) in, up, around and back down. The heat transfer baffles just get warm from your shower water, cooling the water, and then the heat transfer baffles warm your towel.
Just a guess, the labor cost for running the piping to that linked device has *GOT* to cost more than those towel warmers by themselves.
(left wing rant....) If I knew who to send it to, I would submit a nomination of that device for the most un-"Green" energy waster and anti-energy conservation device for the year award. If this towel warmer really does use shower hot water to heat towels, this would be just flaunting your disrespect for energy conservation and your part in making an effort to reduce greenhouse gases. May your children grow up to be environmental warriors who publicly denounce you (after your kids are properly indoctrinated and rote taught the catechism of environmentalism in the public schools of course.)
{hee, hee, hee, the flame wars have begun... Anyone up to starting a popcorn and peanuts concession for the lurkers? I know I shouldn't taunt 'em, but it is so easy to get them anymore. }
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I think he is asking about a standar radiator. Both inlet and outlet are on the bottom but yet they heat evenly across the entire radiator. I've never disected one so I don't know if there are baffles inside.

(right wing reply) Rather than go off on a silly rant, it makes much more sense to find out how things work and why. In Europe especailly, those towel warmers you see as wasteful are the only source of heat in the bathrhoom. They are only on when the house boiler is heated the house. They are very utilitarian and sensible as they take a necessity and at no additonal cost or energy and make it into a luxury.
Many years ago when radiators were common, I know of people that would put ther towels on them, or even the pants they wre going to wear the next morning. This just limits it to towels, but the same idea. Smart eh?

And so silly now that you know the facts.
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---------------------------------------------------------------------------------------------------------------------------
Judging by this link < http://www.runtalnorthamerica.com/towel_radiators/omnipanel.html

There are two types of 'Solea' towel warmers which otherwise are just like any other radiators?
a) Electric in sizes up to 700 watts.
b) Hot water (hydronic) in sizes up to 7,920 BTU* which would be fed from a normal house hot water heating system.
(Which normally involves an electrical pump to 'push' the water around the heating system; including, if fitted one of these towel warmers. The internal construction of the towel warmer is not shown but presumably, within the hot water version there is baffling etc. to direct the water flow evenly through the different sections.
There is as far as one can see; not a steam/condensing version?
So If one were fitting new heating I guess you could use one of these to heat your bathroom; it is after all a device to radiate warmth and heat the air surrounding it. For example our small bathroom is heated by a 500 watt baseboard, with it's own thermostat, and also a row of six 40 watt bulbs (Total 240 watts) above the vanity mirror. When the bulbs are on the 500 watt heater rarely cuts in!
Note: * 3920 BTU per hour is roughly equivalent to to a 2000 watt (2 kilowatt) electric radiator or baseboard heater.
There is no reference AFIK in the original post about routing the shower water through the towel warmer????? Also it does not appear to be a heat recovery device; e.g. warm shower water out heating colder water going in????????
What was that all about?
As a personal comment about the Solea product; not sure I'd want all that 'piping' hanging on the wall! Not from a weight point of view but just the complexity and appearance/cleaning! We do very well with an approx 40 inch single bar fastened above the 500 watt baseboard. Dead simple, easy to clean and maintain!
BTW see my post about "Worth leaving shower/bath water to cool down?"
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No flame wars. I'd just point out that normally you'd only want the towels heated in the winter. In which case, the heat is not lost, it goes to heating the house.. And all the ones I've seen that use hot water, appear to use water in the heating system loop. So, it's more like having a additonal small radiator or putting your towels on the existing one, etc.
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On Feb 15, 8:54am, snipped-for-privacy@optonline.net wrote:

Oh and as to how radiators work, I believe the old cast iron water heaters were connected in sections with openings for water flow at both top and bottom. Hot water went in at bottom end, out the other, and relied on convection to move the water around as well as conduction via the cast iron.
Obviously there could be different flow designs for diff radiators. The baseboard style just use a pipe with fins. Not sure how the towel warmer works. It looks like it might just have hot water going up one side and then back down that same side, then rely on conduction to warm the bars?
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Id guess hot water and heat rises, the metal quickly conducts, warms through out from the water, water cools fairly fast, cools mixes and falls.
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Water heater, and radiator are two totally different things. Would you please choose one or the other?
--
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I'm sure that the radiator completely fills up with hot water. It's not convection an it's not conduction. It's some kind of flow trick that I am trying to figure out. So does anyone know?
Aaron
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Yes, I do know and it has already been explained by me and others.
Why would you assume it's not conduction? There is, of course, turbulence in the water stream which mixes up the water to some degree. If it's not conduction at work, then the pot of water you put on the stove would only get hot on the bottom "layer" of water. You shouldn't look for tricky explanations when simple ones are the right ones.
BTW, how do you "trick" heat flow? Please let me know as I am keen on stopping entropy (the heat death of the universe) in its tracks before it is too late.
R
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On 2/15/2009 8:59 AM RicodJour spake thus:
>

Well, I think it's a valid question too, and especially interesting since the way an old-fashioned radiator seems to be counterintuitive. I mean, based on what we all learned about heat in grade school, the inlet should be at the bottom and the outlet at the top, right? Otherwise, one would expect at least part of the radiator (the part above the outlet) to be somewhat starved of heat.
I *think* what he's asking about (correct me if I'm wrong, O.P.) is whether old radiators were constructed with any type of baffles, flow directors, etc., to make the hot water or steam flow through the whole thing.
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OP here. Yes, that's what I am asking and I am still at a loss.
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Aaron Fude wrote:

Hi, One thing if it is not filled with water 100%(if there is air pocket) it won't heat at all. Take this as a clue.
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Not true in my case. On our hydronic system, when there was not enough pressure in the system (it has since been raised) to fully bleed the top floor radiators, those radiators were hot about 3/4 of the way up on all the tubes and supplied plenty of heat.
--
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On Sun, 15 Feb 2009 08:46:30 -0800 (PST), Aaron Fude

A flow trick? Yep, how did you know? Only magicians know the answer. Maybe trader can help you on this one? Bubba
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What I have experianced is, upright cast iron radiators only fill completely with water when you manualy remove air with the bleeder valve, and have enough water pressure to do so. At least all cast uprights that I have seen must be manualy bled. They will get warm-hot with air in them, not fully hot, usualy I can feel where air starts as its cooler where air is trapped.
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On Sun, 15 Feb 2009 09:48:56 -0500, "Stormin Mormon"

I think he actually said (and meant) "hot water heater"... not one of those things that heats water to make it hot, but something that heats surrounding air using hot water. It's the first time I have seen someone use "hot water heater" in this NG without it being wrong ;-)
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snipped-for-privacy@neo.rr.com wrote:

Had he used "hot-water heater" (compounds in attributive use), we'd have all known what was what.
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