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superlen · 11-25-15, 08:53 PM

AC,

Thanks a ton for those two pics. I noted much earlier in this thread the discussions on the "turbulent sweet spot" & tabled it as I didn't quite wrap my brain about how one could get a little bit of the best of both worlds. I was planning on doing some more research on it, but was striking out in the google department.

It seems one could do a real world test with some of the new variable speed pumps by monitoring GPM & instantaneous power. Slowly bring the speed up and map the GPM vs Power. At that spot where the drag coefficient takes a dive, we should see a corresponding dip in the power required. It of course should be somewhere around the theoretical GPM to put us at that laminar/turbulent boundary. That may be a fairly wide range as I have seen Reynolds numbers anywhere from 2000-4000 as the boundary.

Given a good solid consistent EWT and measure the LWT and we could also plot the heat rejection at the same time & learn something about how sensitive heat transfer is around that boundary. I think that the increased transfer from the water to the tube due to the turbulence may be overshadowed by the extremely slow transfer from the plastic to/through the dirt. As you have mentioned & I like the analogy...molasses slow transfer into the dirt.

Len

11-25-15, 08:53 PM	#1812
superlen Helper EcoRenovator Join Date: Nov 2015 Location: NW Arkansas Posts: 37 Thanks: 5 Thanked 7 Times in 7 Posts	AC, Thanks a ton for those two pics. I noted much earlier in this thread the discussions on the "turbulent sweet spot" & tabled it as I didn't quite wrap my brain about how one could get a little bit of the best of both worlds. I was planning on doing some more research on it, but was striking out in the google department. It seems one could do a real world test with some of the new variable speed pumps by monitoring GPM & instantaneous power. Slowly bring the speed up and map the GPM vs Power. At that spot where the drag coefficient takes a dive, we should see a corresponding dip in the power required. It of course should be somewhere around the theoretical GPM to put us at that laminar/turbulent boundary. That may be a fairly wide range as I have seen Reynolds numbers anywhere from 2000-4000 as the boundary. Given a good solid consistent EWT and measure the LWT and we could also plot the heat rejection at the same time & learn something about how sensitive heat transfer is around that boundary. I think that the increased transfer from the water to the tube due to the turbulence may be overshadowed by the extremely slow transfer from the plastic to/through the dirt. As you have mentioned & I like the analogy...molasses slow transfer into the dirt. Len