[redleader]

10, 20, or 50 watts is just that - watts. Heat is heat, isn't it?

Not really. A watt is a unit of power, not heat. Joules are heat. Generally we just deal with power and temperature since its easier that way. But I get your point about thermal equilibrium. Its just that the change in coolant temps isn't all that significant. Remember the majority of the thermal resistance in a loop is in the block, and increaseing pump capacity decreases the thermal resistance in the block even if it does heat the water more.

Sort of the whole big piece of a small pie or small piece of big pie thing.

Let's look at it in another way. When you increase VCore you are increasing heat output. What? 10 watts maybe per .1 increment (just pulling that completely out of the air to illustrate the point). If a pump dumps just 10 watts into a system, in effect it would be the same as increasing VCore by .X

The effect of increaseing vcore on coolant temps is generally immeasureably small, so I don't see your point. Have you ever tried measureing it? I doubt 10w is going increase water temps more then a few tenths of a degree even in systems with small exchangers.

At that stage it is not insignificant anymore because it is actually costing you higher VCore potential. At least that is how it strikes me as an OC'er. As said, I'm no pro or engineer. Just a country boy tinkerer, but I wonder if this is not a subject that could bear further scrutiny by those that do have this stuff down cold from a proper math and engineering standpoint (and hopefully those that do not lovingly embrace the concept of "conventional wisdom").

How is it significant? What kind of numbers are you estimateing here? I'd say significant would be when its heating the water substantially more then the magnitude of decrease of the temps across the block.

/Add: BTW, redleader, that is not a barb directed at you. Rather one directed at the general BS that gets handed back and around over and over. This subject may not be one of those, but then, it may be.

Something I can say from absolute certainty. There is not one member of this forum who would not appreciate all pumps being reviewed with the added information of how much fluid temp is increased above ambient in a closed loop for a 10 hour cycle, or something similar. Then you could make a better buying decision by knowing:

Pump A is 450 GPH 14 ft head - 11C rise on closed loop cycle/ 55 watts
Pump B is 350 GPH 12 ft head - 2C rise on closed loop cycle/ 12 watts

I know I would sure not be interested in Pump A, would you?

Generally the max power consumption is listed on pumps. Unfortunately this is often far in excess of the real world value, but it gives you at least a very pessimistic upper bound. If you don't trust it, you could always get out a meter and get the exact value yourself. Thats what I did on my 1250, ~9w when hooked up to my loop. A bigger pump will be more, but not so much more that its impractical to cool IMO.

BTW2: I don't have a radiator, I have an external fixed ground loop/sink. I can't turn up the fan to make it better.

I don't have any experience with such systems, but I'd think a bigger pump would make the most sense here since a reasonably powerful pipe exchanger is probably going to be either restrictive or have a lot of slow moveing parallel passages. Either way more flow would probably help a good deal.

Edit: Sorry I had to leave the library I was typeing this post in and walk a few blocks to another building with a computer. Hence the edit.