That's all good, but what I'm seeing is a claim from myv65 that most of the power (10W for an Eheim 1048) is induced in the water in the form of heat. I don't believe that that's the case, but again, maybe I just can't picture it. I believe that most of the energy appears in the form of the circulating water, fighting its way through all the restrictions, which in turn, creates some heat, but certainly not anything near the pumps power input, or even significantly, for that matter. I don't believe that water rubbing against itself produces much heat at all, and neither does water against any other kind of surface. I believe that the energy induced by the pump, which is seen as water movement, is transformed into pressure against the innards of the cooling rig. Since this pressure is omnidirectional, there is no movement observed, but the work/energy is there.
I believe that the heat that a pump induces in the water mostly comes from the heat from the coils. In other types of pumps, the coils can heat up the driveshaft, which can transmit this heat to the water.
EMI/EMF has to be significant, since it does drive the impeller. Hopefully though, most of that energy is absorbed/converted to the motion of the impeller. It certainly explains why mag drive pumps are 70% efficient, at best.
As for noise, I also believe that it is minimal. It can be simply estimated (roughly) by calculating the amount of power required for a speaker to make the same noise/noise level.
Here's an idea: since the movement of the water is measurable, we can calculate the energy applied, using physics formulaes. What's the equation (my physics is rusty!) to calculate the energy required to move a mass (of water), over a specific amount of time?
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