In reply to Jed Rothwell's message of Thu, 7 Apr 2016 15:04:31 -0400: Hi, [snip] ><mix...@bigpond.com> wrote: > >Perhaps you just misinterpret what he said. It could also be taken to mean:- > >"the output varied between 2.5 and 3.7 kW" rather than that there was a >> large >> error in the measurement. > > >I do not think so. Look at the first table on page 14. The column headings >are "First hypothesis" (2.5 kW) and "Second hypothesis" (3.7 kW). The two >hypotheses are listed on page 13: > >"* that the temperature of the inner cylinder is equal to that of the outer >cylinder. This is the worst-case hypothesis; > >* that the power irradiated by the inner cylinder is equal to that >irradiated by the outer cylinder." > >He should have sorted out which apotheosis is correct, by calibration. > >- Jed
After looking at the report, I come to the conclusion that both estimates are wrong. They are both based on the assumption that the power radiated by the inner cylinder and that radiated by the outer cylinder are additive. This is obviously wrong, since the radiation of the inner cylinder is absorbed and reradiated by the outer cylinder. Hence only the area of the outer cylinder is of consequence (with a correction for the radiation from the end of the inner cylinder, which would increase the power somewhat). Using his formula and figures, this gives a power of 1.758 kW (Ignoring radiation from the end of the inner cylinder), rather than either of 2.468 kW or 3.66 kW. Note that his method also makes use of an "estimated" emissivity, which could also be off. In general I don't think trying to determine power output by measuring thermal radiation is a good approach. However in the year long test, that wasn't the method employed, so I'm hopeful that the results of that test will be more useful. Regards, Robin van Spaandonk http://rvanspaa.freehostia.com/project.html
