Quote:
Originally posted by redleader
NO!
All energy is coverted to heat. Always. If your pump uses 30w under normal conditions, its producing 30w of heat.
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No, some of the energy is transformed in mechanical energy. Airspirit is correct.
The 45 Watts (for example) of energy that is supplied to the pump, in the form of electricity, is used for the most part to turn the impeller. Whatever is NOT used to turn the impeller, appears in other forms and include:
-noise
-heat
-fighting friction (thx Volenti)
-magnetic field (aka EMI, Electro-Magnetic Interference)
Very few, if any, of the things we use are 100% efficient. Of all the power provided to a device, there is always some kind of loss. The best example of this is the lightbulb: it also emits a lot of heat.
Overall, our physics laws apply: nothing is lost, nothing is gained. All of the energy supplied is transformed into something.
As for pumps, to me it's very simple: a pump is a motor. A motor is composed of coils of wire. These coils generate a magnetic field that drives the impeller. If the wire in the coils is a low grade, then it will heat up very easily, but will transmit a magnetic field more efficiently (because it's wound up closer to the impeller). If the grade of this wire is too high, then the magnetic field is not as efficiently transmitted to the impeller, but there's not as much heat.
I think you'll all find that every model of pump is different. This heat, from the motor coils, is transmitted to the water, through the impeller housing. This housing is usually made of some kind of plastic, which is a good insulator against heat, but never a perfect one (depends on the grade of plastic). Plastic is used here because it is cheap, and because it can be used in a (relatively) thin layer, between the electrical coils, and the impeller. This layer needs to be as thin as possible, otherwise there's a loss of efficiency in the transmission of the magnetic field that drives the impeller. Plastic also has this advantage where it does not interfere with magnetic fields.
In terms of efficiency, magdrive pumps are typically around 70% to 80% efficient (Someone correct me if I'm wrong here). So, about 80% is used to turn this impeller, and the rest is EMI, heat, noise and fighting friction. In which proportion, depends on the pump design.
I hope I've helped clarify this issue.
I'm looking forward to Skulemate's figures!