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<... My guess is that the EWP will ONLY work if the water flow path is cleaned up sufficiently to allow it to work ...>
My guess is that we're pretty much clueless. In a closed system, the only impediment to flow is friction which is largely a function of flow rate and some exponential function of the diameter of the "pipe". The irregularities in our system are such that they render any attempt to compute total friction an exercise in mental masturbation. What we need is some expire mental measurement of flow rate under actual conditions (which will involve a flow meter in the system) and then, with the engine at rest (the pump is the only moving part in the system), we can see how much current it takes to achieve that flow rate. Sadly, the pivotal instrument, a flow meter that doesn't disturb the system too much, is probably not available. If someone could come up with a flow meter in a 1.25" line, we could do some expirements. Other than that, we're guessing at numbers like PL and the bumblebee folks ... Jim S.
Ernest Christley wrote:
Paul wrote:
I have a small 12 volt bilge pump for my birdbath/fountain. Mfr claims it moves 640 gph of water. If I divide gallons per hour by 60= gpm should work out to around 10.66 gpm. This is a tiny 12 volt bilge pump that my photovoltaic cell runs, with no battery. (only works when the sun is overhead). You can hold it in the palm of your hand nearly close your hand around it. Seems like it wouldn't take much larger of a motor to push 30 gpm if this puny thing will pump 10+ gpm. It will empty a bilge pretty fast. I realize this is unrestricted water, but still, it has to move all that water out of a boat bilge, and does a fine job. It pumps the water in my fountain too high, had to put a restrictor on it. Paul Conner
Paul, I think one of the factors often left out of the EWP/EDWP discussion is head pressure. GPH or GPM is meaningless without stating what head it is pushing against. I'm trying to remember this off the top of my head, but I compared the water flow and current measurments that Todd gave a while back with a chart that Davies-Craig provided which showed flow vs current draw for various head pressures. I estimated then that Todd's system had about 9psi of head pressure. Most of the flow calculations I've seen arguing that the EWP won't work use a figure of 30psi of head. The two ain't the same thing.
My guess is that the EWP will ONLY work if the water flow path is cleaned up sufficiently to allow it to work. I think Rusty's experiment with using both has a high likelyhood of failure, because he will be using the EWP with the thermostat and the tortured path that the EDWP forces the water through. It will be overwhelmingly convincing if does work with the odds stacked against it so much, but at most will only be a qualified failure.
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