Another interesting observation of the old chimney, is that not only is it about 4 times taller, but the diameter of it increases to at least double that of the short vertical section of pipe that feeds it! Could it be that when they were running this thing at 10KW to 20KW, the volume of steam generated was obviously double to quadruple what it is now, and they needed more volume inside the chimney and a larger outlet in order to maintain that expanding vapor at ambient pressure! Perhaps this is obvious to everyone and why its never been mentioned, but if the diameter of the chimney outlet is not large enough to allow the vapor to escape as fast as it is being generated, then pressure will begin to increase inside the chimney... But as pressure builds up inside, it increases the flow rate thru the outlet, which reduces the pressure inside... And so the system oscillates about some mean... Apparently that mean is ambient.
Here's something else to consider... pressure building up inside is not necessarily an indicator of steam quality coming out. Yes, just as in a car radiator, increased pressure raises the BP, and so the steam inside the chimney may contain significant liquid water, but as soon as that steam escapes to ambient, the liquid content will immediately vaporize -- ever make the mistake of opening the radiator on a car when its at operating temperature!!! A very unpleasant experience I assure you... -Mark
