Rich, /please/ */STOP CROSSPOSTING!!/* It's a violation of list rules and it's a pain in the neck when responding!
On 02/08/2011 12:15 PM, Rich Murray wrote: > When it reaches the necessary power transfer to vaporize all the > water, the increase stops abruptly; > 5% more power would increase the temperature of the steam by 60C. > OMG I totally missed this!! *No, Jed, this observation isn't nonsense* -- you need to think this through. It's the difference between a voltage source and a current source. We've been looking at this as though it's a voltage source, but it's really a current source, and the alleged behavior /doesn't make sense/. If the heater power level is fixed, but the water flow rate is allowed to vary, the rate at which water boils away will be determined by that power level. Steam will flow out of the system at, or very near to, 100 C; the amount of steam will be determined by the power level. /That's what we see when we boil water in a teakettle./ It's what we /seem/ to see in this system, as well. If the water flow rate is fixed, and the power level is allowed to vary, then, if steam is coming out, its temperature will vary, and will be determined at any moment by how much larger the power is than the absolute minimum necessary to exactly boil away all the water. In this case, the flow rate is fixed by the positive displacement pump at what seems to be an arbitrary value, and the power level is whatever the reactor puts out. It's an enormous coincidence that the temperature of the effluent was within 2 degrees of boiling. You would think hitting it that close to "on the nose" would require very careful tuning of the input flow rate, or it would require some kind of feedback control of the pump. Neither is present here, as far as I can tell. I have a hard time with coincidences of that scale. ------------------------------------------------------------------------ As to the weight issue of the hydrogen bottle, it's perhaps worth asking who handled the bottle after the experiment and before it was weighed. But really, that's a separate issue. The thing that stands out like a sore thumb, now that somebody had the sense to point it out, is that it should have been /difficult/ to hold the output temperature that close to boiling. It is not a natural result of this setup, in the least.
