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BillA · 11-13-2002, 01:44 PM

for completeness copying myv65's initial post
quote
Since87,

LOLOL. Anyone, and I mean ANYONE that works with real centrifugal pumps would tell you that power goes up with flow rate. This is true despite the lower head that you get at higher flow. All ya gotta do is look at a pump curve that includes power and it'll be obvious.

What I can't quite get is safemode's insistance otherwise. I don't frequent OC that often, but generally thought the guy was OK with heat transfer and thermo. Obviously pumps aren't one of the guy's strengths.

Fact of the matter is that the lowest energy consumption you'll ever get is when you dead-head a centrifugal pump. The highest you'll ever see is when TDH is zero. Peak efficiency is the funky one, as it peaks at different flow values for different pumps. Rarely will it exceed 90% in the best industrial pump. Aquarium-style pumps would be hard pressed to exceed 50%. Given the setups people tend to favor, I figure most water cooling pumps are in the 30%-40% range.
end quote

there are several ways to run at this 'pump power' issue, and I seem to be able to make an unintelligible mess of them
that said, a brief description of my difficulty (and I think Since87, it will come round to yours)

in 'looking' at a heater/wb/coolant system - as a black box, the input power can be calculated and the output power can be calculated

a physicist friend is slapping my head saying: no, its not so simple as the pump is inputting 'power' into that black box via the friction and the pressure drop

had great difficulty with this until another engr 'splaned to me that the 'power' associated with the pressure drop could be measured using the I*E differential at the pump motor

I'm not so sure that experimentally such can be done (substitution with a straight pipe yields also a flow inequality)

separate aspect: I can speak to pump heat generation (but not quantification)
by placing an oil cooled aluminum bodied pump within a heat bath, its heat generation can be observed at different flow rates
- restricting the pump's output causes it to 'create' MUCH more heat than in a 'free flowing' condition

myv65
care to comment on the heat balance aspects of the wb pressure drop ?

11-13-2002, 01:44 PM	#4
BillA CoolingWorks Tech Guy Formerly "Unregistered" Join Date: Dec 2000 Location: Posts: 2,371.493,106 Posts: 4,440	for completeness copying myv65's initial post quote Since87, LOLOL. Anyone, and I mean ANYONE that works with real centrifugal pumps would tell you that power goes up with flow rate. This is true despite the lower head that you get at higher flow. All ya gotta do is look at a pump curve that includes power and it'll be obvious. What I can't quite get is safemode's insistance otherwise. I don't frequent OC that often, but generally thought the guy was OK with heat transfer and thermo. Obviously pumps aren't one of the guy's strengths. Fact of the matter is that the lowest energy consumption you'll ever get is when you dead-head a centrifugal pump. The highest you'll ever see is when TDH is zero. Peak efficiency is the funky one, as it peaks at different flow values for different pumps. Rarely will it exceed 90% in the best industrial pump. Aquarium-style pumps would be hard pressed to exceed 50%. Given the setups people tend to favor, I figure most water cooling pumps are in the 30%-40% range. end quote there are several ways to run at this 'pump power' issue, and I seem to be able to make an unintelligible mess of them that said, a brief description of my difficulty (and I think Since87, it will come round to yours) in 'looking' at a heater/wb/coolant system - as a black box, the input power can be calculated and the output power can be calculated a physicist friend is slapping my head saying: no, its not so simple as the pump is inputting 'power' into that black box via the friction and the pressure drop had great difficulty with this until another engr 'splaned to me that the 'power' associated with the pressure drop could be measured using the I*E differential at the pump motor I'm not so sure that experimentally such can be done (substitution with a straight pipe yields also a flow inequality) separate aspect: I can speak to pump heat generation (but not quantification) by placing an oil cooled aluminum bodied pump within a heat bath, its heat generation can be observed at different flow rates - restricting the pump's output causes it to 'create' MUCH more heat than in a 'free flowing' condition myv65 care to comment on the heat balance aspects of the wb pressure drop ?