Coolest running pump?

Doesn't some energy go into physically moving the water? If a pump converts 100% of the input energy to heat, then no water would get moved.

In other words... in order to get a certain mass (m) of water moving at a certain velocity (v) you need E = 0.5mv^2 joules. I have always viewed the efficiency of a pump as the proportion of the input energy converted into water movement. Most of the energy not put into moving the water is lost as heat, so the most efficient pump is also the coolest.

 

Yes, a ball valve or for even more precise controll, a gate valve.
NOT a dimmer switch!

 

How so? The only thing sticking out the pump motor is the shaft that is attached to a separate impeller housing. There's usually a fan in back of them that air cools them. Also some heat sink type fins. other than that no water cooled motors that I know of.

 

Hat size tank is this for?

 

If it is a true external only pump it may not be product or water cooled and rely on a motor fan or external cooling fins.
If it is a pump that can be submerged or external either one, they are almost always product or water cooled.
Even many external pumps still have issues with heat though. They have a steel shaft and that shaft gets hot during use, transferring heat to the pump end, volute, inpeller or magnets and heating the water.

You want to find a pump that moves the most water per watt consumed as it will be more electrically and hydraulically efficient and create less heat. Less efficient pumps consume a lot of power which is lost to electrical inefficiencies and resistance which equal heat generated. Personally I have found Eheim, Ocean Runner and now Water Blaster pumps to be very efficient and run very cool and quiet compared to comparable Mag, Quiet One, Rio and Via Aqua pumps, all of which I tested myself in an unofficial comparison several years ago. I used a 1" flow meter, Kill A Watt meter, gate and ball valves, PVC piping and tubing, a digital thermometer and several large containers plus my in ground swimming pool for the testing.

 

Yes it does, but all energy decays to heat. You are moving water which makes friction which eventually will slow everything to a stop. Since the tank is a closed system, then all the energy added by the pump ends up as heat.

 

What AZ said. The vast majority are not air cooled. And just because they have fins, does not mean they are, or that they are transferring much heat by them. You could put a fan on it, but that is more power use... you would get more cooling just by putting the fan on the sump for evaporative cooling.

You have to look very close as to what is an true air cooled external pump. all the common ones we use are not.

 

Gate valves are not meant to be throttled, but for PVC ones it does not really matter. Gate valves will give more linear flow control, but most times you will have to order one.

For a return pump, a ball valve is fine. You are usually more than 50% into it's range and you will have plenty of control. If it was something that needed fine tuning control regularly, a ball won't give that to you... but that is not what you need for a return pump. Set it where you want it and forget it.

 

I have been using a Waveline DC 5000 pump for about 6 months now, I highly recommend it. Quiet and 1320 GPH max at 40 W is impressive efficiency. The controllability also comes in handy as there is no need to turn valves to adjust flow.

Aquariums are not closed systems though... they lose matter and energy via evaporation. I am still skeptical a 90 W pump will heat the water to the same temperature as a 90 W heater. Especially since a heater contributes less to evaporation than a pump, since the pump will agitate the waters surface.

It would be a fun experiment to do

 

The system will loses heat to evaporation and radiation, but moving water has kinetic energy. Nnothing moves forever. What stops it is friction. If the energy put into moving the water does not end up as heat, where does it go? It adds energy to the system expressed in watts.

And yes, I've done the experiment, and yes, it's the same.

And a pump and a heater have no bearing on evaporation. Evaporation is set by temp, and vapor pressure on the surface. Water movement ensures a homogeneous temp, but with no movement the 90w coming from the heater will drive the same rate of evaporation given the same circumstances. Watts is a rate of energy conversion... 90w in an hour into the tank is 90w in a hour no matter the device.