On Tue, May 10, 2011 at 9:12 PM, <mix...@bigpond.com> wrote: > > > This is based on the assumption that the actual operating temperature is > indeed > 400C @ 15 kW. If it's in fact much less, then 130 kW for a short period may > not > be a problem. Perhaps it only gets up to 400C when the output is really > high? > > That's true, so we can try to work in the other direction. If it's 400C @ 130 kW, then at 15 kW it would be 370/9 + 30 = 70C. That seems rather low to be able to heat water flowing through at 1 L/s by 5C.
Taking the temperature at 1500C (mp of steel) for the 130 kW spike, would give 1470/9 + 30 = 190C at 15 kW. If the heat is transferred through copper, then the limit would be its melting point at about 1100C, giving about 150C @ 15 kW. Those values still seem pretty low, but maybe it's possible. One can also try to calculate the necessary area required to transfer the claimed power. The range of heat transfer coefficients for liquid water is huge, but even at the highest value I found (10,000 W/m^2K), this would require an area of 1.5 m^2 to transfer 15 kW at 40C temperature difference (70C), or about .38 m^2 at 160C temp difference (190C). For a one inch id pipe, this would require a 5-m length or 1.2-m length for the two cases. Both seem hard to believe. On the other hand, for a temperature of 1000C, you could get 15 kW with a 20 cm 1" pipe. That begins to be believable, but rules out 130 kW.
