I will copy and paste a comment by a user called GoatGuy, who frequently posts on the blog nextbigfuture, and which seems to debunk the e-cats. I would like to add that I do not necessarily endorse his opinion but I would sincererly like to find any counter points to what he wrote there, because I cannot (In fact I also thought of these things, and if a good counter point is given, my last bits of skepticism will be crushed):
http://disq.us/2cavmp ********** Visualize a watering hose. Pretty obviously, if 5 meters per second of water is entering the hose at one end, no matter how long it is, provided the open end is the same diameter, the same 5 meters per second of water will come flowing out. You might object, "but steam is a compressible fluid!" — true enough. The pressure of the steam though will rapidly achieve a balance where that emanating from the open end will have just about the same pressure as the atmosphere. Therefore, at 1 atmosphere, whatever the cross-section × the flow rate is, is the quantity, in liters, of steam. You might object again, "but the hose will conduct heat away, condensing the steam, and resulting therefore in a lower flow at the open end!" — again, true enough. This one is harder. There's a relatively simple equation: Q = KAΔT/x where [Q is heat flow in watts], [k is thermal coefficient of (rubber)], [ΔT is temperature diff between hot and cold sides of material] and [x is thickness of material]. So again, looking at the video clip, I estimate the output hose is 2 cm outside diameter. Inside diameter is 1.25 cm. Thickness (x) is ($thickness = (2.0 - 1.25) / 2 / 100) = 0.0037 m. Average area per meter of hose is ($area_per_meter = 3.14 × (2 / 100 + 1.25 / 100) / 2) = 0.051. Remembering that the hose will be hot (i.e. in thermal equilibrium with the surrounding air, a surface temperature of perhaps 60°C), and a k of 0.16 (from wikipedia for black rubber) then: ( $watts_per_meter = 0.16 × $area_per_meter × (100 - 60) / $thickness) = 87.1 watts In lab I've found it derated somewhat further, to about 50 watts per meter for common lab tubing, with steam inside and comfortable lab air on the outside. So, if a length of tubing is 3 or 4 meters long (per that longer video with the blue bucket…) then it should be conducting away about (50 × 3) = 150 W of heat. This will derate the system accordingly. Now, moving along to the “blue bucket” video case, it looked to me that the exhaust was decidedly watery (as expected from the above dissipation phenomenon.) But it also did NOT look like the effluent steam was very strong. Further, when it hit the bucket of water, it merrily bubbled, but not all that significantly. The ammeter on the floor, near the wall socket showed 1.5 to 1.6 amps of draw. Assuming that most of this went to the heater, corresponding to Rossi's earlier statements of 300W to 400W of heat, that gives (300 W — 150 W) watt of steam per second, which in turn corresponds to a flow of about 1 to 1.5 meters per second. this seems to be similar to that effusing from the tube. Rossi is heard to say directly, "it seems to be stable, and running at about 2,500 watts of output". (Paraphrased). So, let's do that, yes? ($milliliters = (2500 W - 150 W ) / 4700 W × 3120 ml/s ) = 1,560 ML per second, expected, including the hose losses (which are only 6%). Now, working with that 1.25 inside diameter, area is ( $cross_section = 3.14 × (1.25 cm / 2) ↑ 2 ) = 1.23 cm². So… ( $rate = $milliliters / $cross_section / 100 cm/m ) = 12.7 meters per second. 12.7 is pretty damned fast, you know? 2,500-150 watts is substantially more than most “big elements” of electric stoves (1800 W common, and they only deliver 75% or so of the heat to the pot, or about 1,350 watts. This is roughly 2× that level, so it really ought to be whizzing out of the end something fierce. If you want to keep going with the physics side, then there's the impulse (momentum force). You know, like how when you hold a high pressure garden hose with a “jet” nozzle, the hose actually pushes back. The equation is pretty simple: [F = ma] force is mass times acceleration. If the mass ( $mass = 2350 / 4700 × 2.06 g ) = 1.03 g/s is exiting at 12.7 m/s then it net is experiencing 13.1 newtons per second… which is significant. Rossi should be concerned about the danger of the exhaust pipe. Further, and somewhat suspiciously, the “hose and bucket” video showed the docent pulling the hose out of the bucket, where it was not bubbling at all, then the steam begins to come out, and the rate increases substantially over 15 seconds, meanwhile Rossi is out of the picture. When the hose is returned to the bucket, there is substantial bubbling in the water, something which wasn't present before it was taken out. I know I sound too skeptical, but what about that Ignore the man behind the curtain! business? Seeing as his electronic control(s) are entirely digital, it wouldn't take much to kick up the power 10× while the “observers” were looking at buckets and hoses and steam plumes. Like… during those moments, was ANYONE looking at the ammeter? Nah. G O A T G U Y
