On Sat, Dec 10, 2011 at 12:46 PM, Jed Rothwell <jedrothw...@gmail.com>wrote:
> > I was assuming that nearly all of the heat is stored in water, and that > heat stored in the core is insignificant because it is metal, and most > metals have about 10 times lower specific heat than water. I was leaving > out the core altogether. > Water cannot store heat to keep itself boiling even for a moment. Unless the pressure is slowly decreased. Where do you get your ideas? I assume that adding any kind of simulated core will only make the thing > cool down faster. > Adding heat will make it cool off faster? How does that work? > > HOWEVER, if you want to do this test, and you feel the core is important, > you should simulate it. That may mean you heat it up a core separately and > then immerse it in the liquid. Or you put electric heaters into the core, > similar to the ones Rossi uses, and then heat the whole thing for a few > hours until the water boils. I am not sure what material would be a good > choice. Metal, rather than a brick. > Why? Metal has a higher volume heat capacity, but a lower mass heat capacity, and lower resistance to heat, unless you can contain the molten metal. Probably either would work, depending on the actual amount of heat lost in the 3.25 hours. > > >> Conversely, an internal heater would necessarily be more than 100C. If >> there were a slow thermal transfer between the core and the water, as is >> demonstrated by the input power prior to the onset of boiling, the core >> could elevate to much higher temperatures, and continue releasing that >> stored heat, slowly decreasing temperature after power is removed. A 500C >> core and 300C core both produce ~100C water and some amount of steam. > > > I knew that, but as I said, I figured a 500 deg C metal core would have > less thermal mass than an equivalent mass of water at 100 deg C. Even by > volume, nothing holds more heat than water, as far as I know. > Now, you're just not thinking, or feigning ignorance to cling to your point. A 500C metal core may have less thermal energy (relative to ambient) than an equivalent mass of water at 100C, but that's not the point. First, heat flows from hotter to colder objects. That's one of your favorite laws. So, regardless of heat capacities, a hotter metal core will contribute heat to the water. Second, the core might be more massive. After all the device weighs 100 kg, and the water only 30 kg. More importantly, the thermal energy in the water is quite useless as far as keeping the water boiling is concerned. It doesn't contribute at all. What matters is simply the amount of thermal mass stored in the core, and the rate at which it is drawn down. The comparison to water is irrelevant. And for your simplified scenario, where you only consider the heat lost through the insulation, a few kg of either would supply the necessary heat with a 500 hundred degree temperature change, and 10 kg of brick would require only a change in the temperature of 200 degrees. That's still only 10% of the mass of the device. > It would be unrealistic to make the simulated core more than 500 deg C. I > do not think Rossi's electric heaters can make it hotter than that. > > Well, 500C would be enough for 5 - 10 kg of fire brick, or maybe 10 - 20 kg of copper or iron, or only a few kg of sodium nitrate. (Again in your simplified scenario; more is needed to account for the flow of water through the ecat.) And why is more than 500C unrealistic? The elements on a stove are much hotter than 500C, and they're heated by electricity where cooling is efficient. Inside the ecat, with > 2.5 kW power input for 3.5 hours, and very little power out, something has to get pretty hot. Finally, how is "I do not think…" supposed to represent an argument when you say it about the feasibility of heating unknown materials in an ecat, but "It's almost certainly impossible" means nothing when most nuclear physicists say it about cold fusion?
