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Unread 05-19-2007, 01:08 PM   #248
bobo5195
Cooling Savant
 
Join Date: Aug 2005
Location: uk
Posts: 400
Default Re: How much pump is enough? How much is too much?

Quote:
Originally Posted by muffy
i think i'll refute the bases for this post on how much heat is created by the pump . sure you will loss output power than the input power and a % of it will be loosest as heat but this is not the biggest factor. Most of it is loses in the inefficiencies of how a motor works .. A motor works because a current is passed though a wire around the Satator which creates a magnetic field which then attracts or repels the magnets in the rotor which creates a rotation . The losses involved in this process is where MOST of the electricity is lost not to heat . i believe that this post shouldn't be a sticky cause it's not based on fact . and therefore should be "DE-stickyed" as it's putting alot of people wrong. i agree with the general idea of the post but may it should be re-written with theoretical pumps creating theatrical heat.
Motors are indeed inefficient and how inefficient they are could easily be determined by graphs of performance in operation (or getting graphs for similar motors if these are not available). Although any graph won't tell where the heat goes which is the question you are shooting for.

Pumps tend to have a large amount of sealing apparatus on moving components and this will contribute a large amount of friction which I believe you are ignoring. Heat generating by this is very much more likely to enter the water than heat from the motor. Therefore this is likely to be what is warming up the water in the pump.

I'm not exactly sure that sound and vibration can be completely ignored in terms of losses. Doesn't sit right but that maybe cos im eating a burger.

Either way i think i may have said this before in a thread somewhere but a pump is not a right fit (including if it is too big):
- operating in a weird part of its range i.e. running two fast or two slow.
- if you are pumping too much / too little mass flow of water compared to air going through your fans. A little bit on the air excess side is better thermodynamically. A little more water is better noise wise.

Has anyone tried putting a pump in a sealed chamber and letting it get very hot. A insulated pump is not transferring heat to the air. So heat is forced to travel to the water. Compare insulated and uninsulated cases and you've got some nice numbers to work off. For extra science points put thermocouples on bits of the pump. the bits that get relatively hotter may indicate what is putting heat where.
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