> From: "David Roberson" <[email protected]> > Sent: Friday, August 16, 2013 2:39:12 PM
This is a quick response .. I don't have time right now to dig up my old posts. See my document on steam at lenr.qumbu.com for steam quality. > > I have seen various tubing sizes tossed around in regard to the > recent video demonstration. Does anyone have direct knowledge of the > inside diameter of the copper cooling tubing? The OD looked to me to be about 20mm ... I guess the ID to be in the range of 15mm to 20mm. I think the length on each side (inlet,outlet) is about 10m > Since .5 liters per minute of cooling water flow was demonstrated in > the Argon test, let's assume that this flow rate was accurate for > the flow rate when the hydrogen was used. It was apparent that the > tubing could handle the assumed .5 liters per minute with no problem Assuming 20mm ID the flow could be as much as 12 l/min -- allowing a 25C delta T with non-scalding 50C output, if you want to go to 99C sub-boiling, 75C delta, only 4 l/min would be needed. Various pressure-drop / water velocity tables showed that 12 l/min in 20mm ID is a high but feasible flow rate. Hadjichristos said the limit was mains pressure (after two and maybe three filters). Pure mains (typically 50-80 psi) might be able to do it .. but I'd go for a metered high-pressure pump. > so the question becomes; what effect does the conversion to vapor > have upon that behavior? > I noted that the temperature languished at 100 C for a long period of > time as the system was coming up to power. This would be consistent > with the condition of water passing through that is being vaporized > at atmospheric pressure. Initially it would be expected to remain at > that temperature and flow rate as long as the vapor is not > restricted significantly by the pipe friction losses. This is where > we need some knowledge of what should happen at elevated > vaporization rates. The heating goes in three stages : a) Water heated to boiling : temperature rises from 25C to 99C ... this is pure water flow. b) After boiling (say 100C) is reached, the temperature stays the same, but the quality of the steam increases from 0 (totally wet) to 1 (saturated). As far as flow is concerned, this is tricky, as you have intermediate stages : b1 -- Mostly water, with bubbles. Will act mostly like water, ie smooth flow, the water will look a bit cloudy b2 -- Water with voids -- the volume will increase, pressure may go well above ambient because the water restricts the flow -- the output flow will become irregular .. mostly water with intermittent bursts of steam b3 -- Steam with plugs -- steam is now dominant, the plugs will be ejected forcibly, sputtering at the output b4 -- Steam with droplets (what I call dry-out) -- the steam will flow quickly, with the droplets just carried along -- you will see "visible" misnamed "steam" at the output Between b1 and b3 you could collect liquid water at the outlet. The volume of the mix, and therefore the flow rate, increases linearly from pure water to pure steam. c) Saturated steam -- temperature rises from 100C to (observed) 165 C : you will NOT see steam at the outlet ... it will condense into a visible plume a few cm out. Pressure tables (20mm ID, 10m length) indicate about a 0.5 bar drop along the tube. Sparging will work at any of these stages. > It should be noted that the net flow rate of cooling water through > the device is the same whether or not the water is vaporized by > conduction of heat from the device if we assume that the meter at > the input reads correctly when reverse pressure is applied. I would > like to find a method of estimating the reverse pressure that is > expected due to the vapor flow as heat is applied. Does anyone among > this group have a good understanding of the pressure drop generated > by flowing vapor in a condition such as we are observing? Is there > reason to believe that several bars of reverse pressure is present > at the output thermocouple at the maximum power point? I don't think that reverse pressure to the flow meter is going to have ANY effect. > My main issue is the apparent lack of noise being generated by the > vapor exiting the tubing into the sink. This may just be an error in > expectation on my part, but perhaps others share that concern. See above .. the sound and appearance at the outlet goes through several stages, and merits close observation (Jed's dark screen etc) > The purpose of this post is to attempt to apply logic to the > observations from the demonstration. It would be interesting to > squeeze as much information as possible from what was shown. Please > offer any evidence or knowledge that you might harbor as we pursue > these ideas. > > > Thanks, > > > Dave
