David Roberson <dlrober...@aol.com> wrote: Jed, is it possible to calculate the amount of power that is being added to > the water by looking at the system? I assume that the water is not moving > just prior to being accelerated to finally reach the speed that it is > moving inside the pipe. That may allow you to calculate the kinetic energy > that must be imparted to it which would be deposited into the far tank.
It is continually looping around. The only work the pump needs to do is to overcome friction. It has to lift the water a short distance, but the water in the pipe is a siphon; the water goes right down again. The pump is just above the Dewar. > The frictional losses within the pipe would have to be supplied by the > pump as well. That heat would likely end up within the water instead of > conducting through the hose surface. > To measure this, you can run water through a 16 m plastic pipe, 1 cm in diameter at 8 L/min. I promise you will not find any measurable temperature rise from the friction. Put the coil in a well insulated envelope. > A good first start would be to calculate the kinetic portion of the pump > power. It does make me curious as to where they assume the 3 watts is > being dissipated. It turns out that is for another model, the MD-6. This is an MD-6K-N, smaller, only 12 W max. It is not listed in the spec. sheet except to say, "Note: Bearings are not used on MD-6K-N/6ZK-N/10K-N models due to their small size." http://www.iwakipumps.com.vn/doc_viewer.aspx?fileName=/upload/file/md.pdf I assume that means the bearings are not as good, so the ratio of input power to output mechanical power is probably worse than 6:1. As I said, Mizuno just measured the input electrical power at 10.8 W. I am guessing the ratio is 20:1 (~0.5 W delivered) because otherwise we would have seen the heat show up, I think. I just looked at a 39 min. segment. Ambient starts higher than the water: 24.64 vrs. 24.54 deg C. Ambient goes up, the water does nothing. Then after 20 minutes ambient falls, the water does nothing until it abruptly rises a little, about 0.08 deg C. Then it is flat. At the end ambient is 24.24, water 24.68. That does not look like ~1 W to me, but with all that noise who knows. There are currents of warm and cool air blowing around and two gas heaters. The ambient around the reactor could be as much as 0.3 deg C different from what is recorded here. The water is well mixed and I am sure that temperature is right, but I would not try to draw any conclusions from this. Maybe 8 hours of data with nothing but the pump and reasonably stable ambient will tell us something. Anyway, however much the pump is delivering it is not enough to keep the temperature from falling. Whereas after that 39 min segment, when I put a tiny blip of 300 J (5 W for 1 min) the temperature rose from from 24.67 to 24.72 about 20 minutes later. Ambient hardly changed. 300 J over 20 minutes is 0.25 W. Later that day it looked like the first 39 minutes. Random movement by both ambient and slight changes in the water. No clear trend. Certainly not 1 W unaccounted for. It is much too noisy to make any firm conclusions. You can only measure higher power, where the water is much warmer than ambient, and heat losses are in one direction only. - Jed
