On 01/31/2011 09:44 PM, [email protected] wrote: > In reply to Jed Rothwell's message of Mon, 31 Jan 2011 17:37:04 -0500: > Hi, > [snip] > >> Actually, it worked pretty well. These were short tests, of 15 to 30 >> minutes. If you run the test too long of course the water gets too hot. In >> these tests they let the temperature go from 20 deg C up to around 60 deg C, >> to capture about 8 million calories (33 MJ). >> > There is potential problem with this method. When the temperature of the > collection water is low (room temperature), the steam will condense until the > partial vapour pressure of the steam is correct for that temperature. At room > temperature that will be a lot less than 1 atm, so the water in the device > will > boil at the correspondingly low pressure/temperature, i.e. at the temp of the > collector.
This doesn't sound right. If the pressure in the steam boiler outlet tube were to drop to the vapor pressure of water at 20C, you'd get the water in the condenser drum, which is at 15PSI, being sucked back up through the steam boiler tube. (Strange effect, that -- turn on the boiler, and the water in the condenser starts flowing up the hose into the boiler. You'd think somebody would notice...) In short, as long as the drum of water you're running your steam into is open to the air, the pressure in the hose running into the drum can't be too far off from 1 atm either way, which in turn implies you've got (roughly) 100C steam coming out of the boiler. I suppose there could have been check valves in the line to prevent back-sucking -- but even then, the check valve isn't going to open until the pressure hits 1 atm and again, you're looking at 100 C steam coming out of the boiler. It would be interesting to figure out what the exact heat flow is, and what parts are at what temperature -- but unless the water's going through the system the wrong way, I think we can be pretty sure the boiler, at least, is running pretty close to 100 C. > That means it takes less energy to boil the water than one is using > in one's calculations. That's why Rossi said you would need a heat exchanger > (reverse flow no doubt), which would ensure that the temperature at the outlet > of the device remained at about 100 deg. C. > > Regards, > > Robin van Spaandonk > > http://rvanspaa.freehostia.com/Project.html > > >
