There currently exist point of use instant how water devices, which mount to the kitchen sink and provide 190F hot water.
There currently exist pot filling devices which dispense water from directly above the stovetop, into your pot.
I propose to combine these two ideas -- an instant hot water pot filler.
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To be sure that the instant hot water device heats the water as fast as possible, it would use an internal burner and a countercurrent heat exchanger, as is done in a tankless hot water heater for a home.-- goldbb, Apr 04 2009 Some popular instant hot water dispensers http://www.google.c...90F+water+dispenserNote that some of the pictures only show the top half -- the working part (the actual heater) isn't shown [goldbb, Apr 05 2009] (1) To bring the water to a boil. (2) To keep it boiling. (3) To help brown ingredients before hot water is added.-- jutta, Apr 04 2009 sp. "howitzer"
other than that, yes please, but put a drain on the stovetop too (empties into a bucket or floordrain), just-in-case.-- FlyingToaster, Apr 04 2009 /Simply attaching one of those instant hot water devices to your pot filler faucet would accomplish what you're after./
You're assuming that a regular pot filler can withstand the 190F water produced by an instant hot water heater.
/And, given that those devices are meant to be attached to a faucet,/
You are confused. Instant hot water heaters do not "attach to faucets."
They are typically under-the-sink devices; the water they produce is routed to a dedicated faucet, seperate from the regular hot and cold water. That dedicated faucet is called an "instant hot water faucet." This type of device (especially if it's gas powered) can take up a significant amount of room.
Some types of instant hot water heaters are integrated water heater / faucet combos. These too are called "instant hot water faucets." The link you provided shows a water heater of that type.
In either case, a special faucet is used, capable of withstanding the very hot 190F water that's produced.-- goldbb, Apr 05 2009 You have me confused : Heating water by 80° (from 10 to 90°), 1 liter, 10 seconds (rather slow for filling a pot) would require a 48.000 Watt machine if i calculated right. how do those on-demand thigies do that?-- loonquawl, Apr 06 2009 **What does this mean please?-- blissmiss, Apr 06 2009 //would require a 48.000 Watt machine//
To my understanding, they usually have a small, insulated tank underneath which holds about a cupful of boiling water ready. In this case, it would need about a potful.-- mitxela, Apr 06 2009 miasere, if you can fill your pot while it's sitting on the stove, then it counts. :)-- goldbb, Apr 06 2009 Just wondering how safe it is to have scalding hot water overhead ? I realize the reservoir may not be overhead, but to dispense water from above the stovetop some part of this would need to be, wouldn't it?
EDIT: and what about the pressurization? Doesn't seem terrifically safe either.-- Noexit, Apr 06 2009 Some pot fillers can take hot or cold water. Maybe not 190F, but at least 140F.
But I get the idea, a pot filler with two valves that can fill that spaghetti pot with near-boiling water, but can fill the same pot with cool water for potatoes. And as I can't find it with google, + and + again.
Now if someone would just invent a smokeless pre-heater grenade for my oven, I can get dinner done in under an hour.-- nomocrow, Apr 06 2009 Maybe I'm just not understanding this, but the point of a pot filler is to fill a pot. If you want the water to be hot, you need to apply sufficient energy to raise the given volume of water to a specific temperature. As [loonquawl] implied, doing so with electricity is probably going to be less efficient (costlier and slower) than if you simply used the burner to directly heat the cold water that came out of the pot filler and into your pot.
Or in short, you already have an on-demand water heater on your stove: The pot & burner. [-]-- justaguy, Apr 07 2009 justaguy, yes the point of a pot filler is to fill a pot. And heating water with electricity is sure to be slower and more costly than doing so with gas.
However, using an open flame to heat a pot that's been filled with water is *not* the fastest and cheapest way of doing it.
The fastest and most efficient way of heating water is to pass it through a countercurrent heat exchanger, just as is done in a tankless heater for one's home.-- goldbb, Apr 07 2009 Still confused - Every POD water heater I've ever seen has been of the type with a small-reservoir heated directly by an electric element. Conversely, the tankless instant DHW heaters (whole house) seem to be a simple gas-fired coil-and-burner arrangement, where the cold water passes through the coiled (or serpentine) tubing that the gas (or oil) burner heats directly.
Are you proposing a new type of POD heat exchanger that uses a countercurrent heat exchange mechanisim, or do you have a linky link to the sort of device you mean to employ?
On that subject, let's talk about efficiency for a moment. Now I'll grant you that heating a pot of water on the stove is not terribly efficient. Let's put that on the back burner (chortle) for now. I also freely admit that I don't know much about CF HX efficiency, but I do know that in order for the H to be Xed, it must first be generated. And I know that some amount of the energy you put into fluid A will be lost in the transfer to fluid B. So how, exactly, is it the /fastest and most efficient/ method when you could simply apply all of those calories to fluid B directly in exactly the same manner as you would apply it to fluid A in the CF HX design?
Seems to me like what you're fundamentally looking to do is find the fastest, most efficient means of heating a pot of water. And really, for practical application, that means water boiling in the pot. I'd be more inclined to address the efficiency issues of one or two dedicated "pot burners" - much like backpackers do with pack stoves - than to turn to a seperate system. Because for the most part, heat exchange efficiency seems to be ultimately reliant on getting the energy from the heat source into the medium you want heated in the least number of steps. But hell, I've been wrong before.-- justaguy, Apr 08 2009 //So how, exactly, is it the /fastest and most efficient/ method when you could simply apply all of those calories to fluid B directly in exactly the same manner as you would apply it to fluid A in the CF HX design?//
[goldbb] really didn't say anything about the monetary efficiency of the idea; this is a convenience item, and one I can think of a bunch of uses for.
It's faster to the person doing the cooking because it is ready when the person needs it. The water is heated on demand or it is held.
It is likely more efficient because:
In an enclosed coil mechanism, the surface area of the water being heated is proportionally much greater and is within a closed, insulated system with little heat loss (as opposed to a pot, where a lot of the heat goes around and up the sides).-- nomocrow, Apr 08 2009 Well, if we're going to go this far, why not have boiling water in a can, so we can skip the stovetop portion all together?
All we would need would be some good insulation and a "Best if used by date xx/xx/xx system . Opening it could be interesting.-- normzone, Apr 08 2009 [nomocrow], the word "efficiency" does not refer to economic efficiency in the context of the quote you took there. The context there was that [goldbb] seemed to be saying that applying heat to one liquid, then transferring that heat to another liquid, is the most efficient means of heating the second liquid. I did refer to economic efficiency in a different context, but let's not comingle the two.
I started to write a lot more stuff here, but it all boils down to the fact that I concede the idea of a hot water reservoir has merit in its time saving ability, but I personally wouldn't want to make that cost-time tradeoff. But I am coming around to the idea of a direct-fired preheater, provided that it was gas in a gas stove.-- justaguy, Apr 08 2009 Justaguy, where you said: /I also freely admit that I don't know much about CF HX efficiency, but I do know that in order for the H to be Xed, it must first be generated. And I know that some amount of the energy you put into fluid A will be lost in the transfer to fluid B./
Well, the problem isn't heat being lost when it's transfered from fluid A (air) to fluid B (water), the problem is that not all the heat is transfered.
Let's say that you take 70F air, heat it to 1800F (by means of combustion), run it through a tank of water by means of a copper coil. Assuming that the thermostat turns the heat on and off quite close to 190F, then we can expect the air to go up the flue at no lower than 190F, maybe higher. All the heat in the air going up the flue is wasted.
If we use the stovetop, we start with air at 70F, mix fuel in and burn (again raising the temp to 1800F), run it past the bottom of a pot, after which the hot air goes into the room, the air going into the room at a much much temperature than 170F ... effectively wasting more fuel.
If we use a counter current heat exchanger, though, we take air at 70F, heat it to 1800F through combustion, and pass it through the heat exchanger in one direction. We then take cold water from the plumbing system (let's call it 60F), and run it through the heat exchanger in the opposite direction. Hot water comes out of the HX at the same side as hot air went in, and cold air comes out at the same side as cold water went in. The air leaving the system can't be below 60F, but it can come pretty close. This exhaust temp is far below the 190F lower limit of the air temp that a tank & coil system would have. Since water is much denser than air, the temperature of the water coming out of the HX won't be anywhere near as high as the temperature of the air entering it, but it can still be pretty high.
This is the most fuel efficient way to heat water, and this is the way that I'm proposing to heat water for the pot filling device.-- goldbb, Apr 08 2009 Baked in commercial kitchens - complete with the stovetop drain as mentioned by FlyingToaster. The last restaurant I worked in had one.-- spidermother, Apr 08 2009 /Well, the problem isn't heat being lost ... the problem is that not all the heat is transfered./
Sorry, still confused. What is the difference between "lost" and "not transferred" in the context of heating efficiency?
Sorry, I should clarify here. The point is not that I inherently doubt the efficiency of a CF HX. The point is that when "liquid A" becomes "Air" and the heating source is open flame, the distinction between what constitutes a CF HX as you describe and a direct-fired coil as I describe becomes semantical, since the more efficiency you seek from the counterflow design, the closer the jets will get to the coil, up to the point where most of the energy of combustion is transferred as directly to the copper as possible.
So again, I have to begrudgingly admit that the idea has merit, and in fact I'm coming to quite like it. My bone has transubstantiated into bun. But my point is that common sense objects to the semantics.-- justaguy, Apr 09 2009 random, halfbakery