Dear Gigi, You wrote:
"The pump absorbs from the grid a given amount of electrical power: for the sake of simplicity let's say 12 W. According to the data sheet 3 W are transformed into mechanical work and, eventually, transformed into heat inside the water. The other 9 W are directly dissipated into heat: part of this heat, as we measured is transferred to the water. It would be hard to say that if the pump wall near the water chamber is at 50°C the heat is not transferred to the water. I do not see any kind of thermal isolator in the disassembled pump. If 1.5 W is transferred to the water everything is OK." Your description above of how the input power is directed leads to a question. Have you contacted the vendor about the assumption that 3 watts of mechanical work is always occurring within the pump section of the device? Does the amount of this heat generation depend upon the pressure that the pump must work into? If so, that is what I assume may be occurring with your substitution of a 5 mm tube when compared to the original 10 mm tubing. The pressure is 16 times higher in your case for the same water flow rate. To be fair, you are suggesting that the system used by Mizuno is also forcing the pump to run at its maximum pressure due to the long tubing frictional loss. This is in contrast to what Jed has been told by Mizuno. I am not sure of the best way to prove your point short of connecting a new pipe that is 10 mm ID and 16 Meters long to the pump. "In a previous message I gave you a couple of links. In the second link, in the APPENDIX you will find the simulation" I sent you a second email where I mentioned that I have found the simulation and am reviewing it. So far, I find it interesting. "I hope now you can remove the confusion in your mind." That is a hopeless task Gigi. :-) Regards, Dave
