Hmm, yes.... boiling.
It's not clear from this article exactly what has been achieved.
They can't be talking about the energy required to bring the water to boiling point, that's an established quantity called specific heat.
Similarly the energy required to go from water to steam is called the latent heat of condensation and is about 540 kcals/litre. So they must be talking about the efficiency of transfer of heat from the metal to the water.
If you put an immersion heater into water, the only place for the heat to go is into the water. So I guess they must be talking about combustion fed boilers. In which case you've got 2 interfaces, flue gas to metal and metal to water. The quicker you get the energy into the water, the steeper the heat gradient and quicker you can suck in more from the hot gas.
30-fold is a big increase tho', I'm surprised that existing systems waste that much energy. There may be an element of journalistic hype.
w
It's not clear from this article exactly what has been achieved.
They can't be talking about the energy required to bring the water to boiling point, that's an established quantity called specific heat.
Similarly the energy required to go from water to steam is called the latent heat of condensation and is about 540 kcals/litre. So they must be talking about the efficiency of transfer of heat from the metal to the water.
If you put an immersion heater into water, the only place for the heat to go is into the water. So I guess they must be talking about combustion fed boilers. In which case you've got 2 interfaces, flue gas to metal and metal to water. The quicker you get the energy into the water, the steeper the heat gradient and quicker you can suck in more from the hot gas.
30-fold is a big increase tho', I'm surprised that existing systems waste that much energy. There may be an element of journalistic hype.
w
wakibaki said:
Please note that this value is quoted at a specific pressure. (As is the temperature at which water boils). As this decreases the amount of water bonded to water, it decreases the enthalpy of vaporization. I'm not sure of the specifics, but that's at least how I read it.
Yes, it would also increase the amount of area available for heat conduction, providing that the water is more pure than any cooling water known to man. I'd give these nanowires about 3 hours before scaling made them inoperative.
BS.
The pressure is irrelevant.
I'm not interested in 'how it works' until I know 'what it does', and what it certainly doesn't do is 'reduce the amount of energy required to boil water'. Since the amount of energy recovered on condensation is always the same, anything else would mean you could build a perpetual motion machine.
If you've got a point to make, make it on your own account instead of trying to ricochet off my contribution.
w
The pressure is irrelevant.
I'm not interested in 'how it works' until I know 'what it does', and what it certainly doesn't do is 'reduce the amount of energy required to boil water'. Since the amount of energy recovered on condensation is always the same, anything else would mean you could build a perpetual motion machine.
If you've got a point to make, make it on your own account instead of trying to ricochet off my contribution.
w
Hi,
the piffle was written by an eejit.
The energy required to boil water cannot be changed.
Similarly the energy required to raise the temperature of water cannot be changed.
The temperature of boiling can be changed with changes in atmospheric pressure and contaminants.
The heat transfer is maybe more efficient, but there are so many errors in the text and the science being reported that I for one would not bet my life on any part of these claims.
Let's see the original scientific text.
the piffle was written by an eejit.
The energy required to boil water cannot be changed.
Similarly the energy required to raise the temperature of water cannot be changed.
The temperature of boiling can be changed with changes in atmospheric pressure and contaminants.
The heat transfer is maybe more efficient, but there are so many errors in the text and the science being reported that I for one would not bet my life on any part of these claims.
Let's see the original scientific text.
http://en.wikipedia.org/wiki/Thermal_conductivity
Thermal transfer is a function of the cross section the heat is moving through, yes? It seems all they have done is create more surface area on the bottom of a pan. Why so small? Who wants to clean a pot with a sponge-like structure on the bottom. It would be brutal on knuckles and not too sanitary.
Isn't the idea of fins on a heatsink to increase the surface area for more effecient transfer of heat from whatever you are cooling to whatever liquid/gas you want to dissipate the heat into? All they did was make a high SA heatsink on the bottom of a pan. No one changed the specific heat or any other law of thermodynamics.
Edited for grammar.
Thermal transfer is a function of the cross section the heat is moving through, yes? It seems all they have done is create more surface area on the bottom of a pan. Why so small? Who wants to clean a pot with a sponge-like structure on the bottom. It would be brutal on knuckles and not too sanitary.
Isn't the idea of fins on a heatsink to increase the surface area for more effecient transfer of heat from whatever you are cooling to whatever liquid/gas you want to dissipate the heat into? All they did was make a high SA heatsink on the bottom of a pan. No one changed the specific heat or any other law of thermodynamics.
Edited for grammar.
wakibaki said:
no. it's not. please see "Carnot engine". (seriously this is freshman thermo)
The energy recovered in the cycle can never exceed the energy in, but it can be made increasingly more efficient based on the temperature inside the cycle. If this lowers the boiling pt of water, it makes it more effiecient, as you don't have to heat the water to 100 C.
wakibaki said:
I was using your "point" as a reference of misunderstanding, which apparently continues blindly.
I would also like to see the actual data and experimental set-up. I am neither accepting or denying this claim, but find the claim unique and possibly a boon for such things as desalination.
Seriously, calm down. This is just a lilliputian version of a pin fin heatsink, no?
http://www.coolinnovations.com
http://www.coolinnovations.com/technology/heatSinks_articles.php
Not too hard to understand, and certainly not worth arguing about. Were we at a Gordon Conference and someone said that cold fusion had, indeed, been generated in their bath tub...maybe we could throw some flags. Forget the writer...look at the principles.
To measure this effect? Propose that you take a 12"x12" CSA vessel with a 0.25" thick bottom plate made of solid copper. Apply heat in your method of choice (propane, alcohol, jet fuel) to one side of the plate. Fill the vessel (other side of the plate) with a known volume of DI water. Measure the water temp until it hits boiling point at given pressure (Sea Level or Mt. Fuji). Calculate fuel expended and energy. Now, do the same with an application of said copper nano rods on the surface. (Height is negligible if they are truly "nano".)
Just a guess at an easy way to check this out.
If the energy expended is the same, your article is a hoax. If not, you have yourself a cool application and a heated (no pun intended) debate on an audio forum.
Peace.
Edited for clarity.
http://www.coolinnovations.com
http://www.coolinnovations.com/technology/heatSinks_articles.php
Not too hard to understand, and certainly not worth arguing about. Were we at a Gordon Conference and someone said that cold fusion had, indeed, been generated in their bath tub...maybe we could throw some flags. Forget the writer...look at the principles.
To measure this effect? Propose that you take a 12"x12" CSA vessel with a 0.25" thick bottom plate made of solid copper. Apply heat in your method of choice (propane, alcohol, jet fuel) to one side of the plate. Fill the vessel (other side of the plate) with a known volume of DI water. Measure the water temp until it hits boiling point at given pressure (Sea Level or Mt. Fuji). Calculate fuel expended and energy. Now, do the same with an application of said copper nano rods on the surface. (Height is negligible if they are truly "nano".)
Just a guess at an easy way to check this out.
If the energy expended is the same, your article is a hoax. If not, you have yourself a cool application and a heated (no pun intended) debate on an audio forum.
Peace.
Edited for clarity.
They are talking about heat flux and the ability of heat to flow from the metal to the water. they characterize the efficiency by measuring the temp difference between the wall and the liquid (Tw-Tsat) and the measured heat flux.
They also reported that in subsequent tests using the same surface, there was degradation in the efficiency, which they called aging behaviour and attributed it to oxidation and the accumulation of impurities.
This statement within the article..""If you can boil water using 30 times less energy, that’s 30 times less energy you have to pay for,” he said. . ""....while in itself is accurate, implies that they required 30 times less energy to vaporize the water, and that is NOT what the origional scientific paper said.
Cheers, John
They also reported that in subsequent tests using the same surface, there was degradation in the efficiency, which they called aging behaviour and attributed it to oxidation and the accumulation of impurities.
This statement within the article..""If you can boil water using 30 times less energy, that’s 30 times less energy you have to pay for,” he said. . ""....while in itself is accurate, implies that they required 30 times less energy to vaporize the water, and that is NOT what the origional scientific paper said.
Cheers, John
Aaron, I don't follow your example here. Your example (a vessel) is a closed system (i.e., it's not a continuous stream of water flowing past), so the energy to boil the water is independent of the surface, it's a constant which just depends on the mass of water.
Now in a heatsink or similar application where there is a continuous flow of fresh "recipient" media, indeed increasing the surface area will increase the amount of energy dissipated per unit time for exactly the reasons that John cites. There's nothing mysterious about that nor any major breakthrough. If practical, it's just an evolutionary step, though nothing wrong with evolutionary steps!
Now in a heatsink or similar application where there is a continuous flow of fresh "recipient" media, indeed increasing the surface area will increase the amount of energy dissipated per unit time for exactly the reasons that John cites. There's nothing mysterious about that nor any major breakthrough. If practical, it's just an evolutionary step, though nothing wrong with evolutionary steps!
Ahh, an electrical analogy is in order. Aaron's vessel is a capacitance, the temperature difference is potential (voltage), and between them is a resistance comprising the thermal conductivity of the boundary medium and the interfacial thermal resistances. It's easy to see that the capacitor will charge to the full voltage regardless of the resistance- the rate at which it does so may be altered, though.
A flow system would be more analogous to a current sink than a capacitor, so it can be seen that the thermal resistances are critical to the total energy input per unit time.
A flow system would be more analogous to a current sink than a capacitor, so it can be seen that the thermal resistances are critical to the total energy input per unit time.
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