What is a good return pump?

[mburnickas]

I disagree just from a basic heat transfer stand point. So for example, I have a large tank, lets say 30,000 gallons. You are telling me that heat from a pump is going to effect that amount of volume? I think not. never mind the surf area that holds the water in that is cooling the water. It comes down to heat rate or heat flux, take your pick. Also the material, Q, the area (A) is constructed of. Plus the delta in temp.
Hell I could figure it out for my tank and graph it with differant variables. Just look up the "K" value for glass, area of glass and some other factors and bingo. This is stuff thet teach you in the first week of a engineer class.
Again heat from a pump is small in the large skiem of a tank. Worry about the larger items first thin worry about the small items.
Again this is un-true if you pump is hot enought to melt the paint on the alu housing.

 

[tony detroit]

You do not have to lecture me about thermo-transfer or fluid dynamics, I went to Michigan Tech and have had enough of that in the ME building. I assure you that a pump can heat your water 5 or more degrees in a matter of a day above ambient air temp, and that is on my 300gal. Think if the pump was on a 125gal.... less water to dissapate the heat to.

 

[bluedolphi]

Pumps do transfer heat. I work with them every day. It is relative. Your 33,000 gallon tank may not have a great rise in temperature with a pump that would normally be used for a fish tank. But the rise in temperature is there. Size the pump for the 33,000 gallon tank so that the gph is equal to the same equations as the smaller fish tank, and the rise will indeed be noticeable. All of the above are measurable.
It is not effected by the glass nor its (the glass) properties for transfer/retention of heat. We are not even including the glass in the experience of the pump owner. Only the water passing through the pump, and the exchange of temperatures from the pump to the water.
Anywho (as in hooo).... I think I'll let this one die, as it is getting a bit off topic.

 

[mburnickas]

I will let this die also but I must say his, because the above post would not satisfy equations in theory and practice. The material DOES comes in to play again basic heat transfer practice; never mind the scale is not linear. So the pump is not linear on a graph. It is not that simple.
Again may things contribute to a temp rise and a pump (big or small) might effect it (again more factors then just a pump come into play). But again, is it adding 0.00000001 KJ to water or 100 KJ to water? Glass comes into play since it is a insulator or lack there of, like all materials. Example it the pump addes 1 KJ ot heat to water, but the glass cools the water by 2 KJ then the pump it is ZERO. In fact the water will cool even with the pump heat. My units are not correct but you get the point.
So the pump does had heat at the start, but in the end you will never see it since the glass area disapates the heat to fast.
I am not trying to beat this out out, but again I do this stuff to "put food on the table" so it might have some validity.

 

[squidd]

CSL Velocity T4...
"They are made with noryl housings and impeller, titanium rotor and separating wall, ceramic bearing ball, carbon graphite bearing cap and EPDM o-ring."
When considering "heat transfer" one needs also look at the thermodynamics of the material suspect of the transfer...
The design of this particular pump minimizes this transfer through separation and non(low) conductive materials in the "pump" area...
Unless this pump is operating at much higher than the 50psi max it's rated for compressive generation would also be minimal...
As an "external" motored pump transient heat from the motor would not transfer to the water...
Unless your "friend" has a defective pump (seized bearings/shaft or impeller/housing tolerance conflict) he may be mistaken as to the source of the temp increase he is experiancing...