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Alchemy · 02-19-2003, 04:39 PM

Wow. Very ambitious. I like it.

I'd go about it this way:

1) Get numerical PQ curves for all the major components - WB, rad, pump - and figure out how to combine the data to determine the pressure drop and flow rate of the system. This might take some iteration for a three-curve problem, but I'm fairly sure it can be done by numerical means. I don't know much programming, but I hope any app you're talking about can run a Newton's method pretty easily.

This will solve the flow rate of the system.

I'd ignore effects from tubing and take care of them later with a correction factor. You *need* to run experiments to test these things for at least a few combinations.

2) Get water-side hA-Q diagrams for the radiator and WB, and air-side hA-Q diagrams for the radiator. Input the Q for the water from (1) and the air velocity from whatever fan you're running. You might find it best to have a list of hA values for each fan, since different fans will have different airspeeds depending on the geometry of the radiator.

This will generate the heat transfer coefficients (hA) for the WB, water-metal interface in the rad, and metal-air interface in the rad.

3) Solve for the overall heat transfer coefficient UA using the hA coefficients from above:

1/UA = 1/hA (rad-water) + 1/hA (rad-air) + 1/hA (rad-cpu)

4) Using UA from (3), the ambient temperature, and the heat output of the CPU (I'm ignoring the pump here b/c it requires running a couple of the above steps again, probably for minimal benefit). From that you can tell:

Heat = UA * (Tcpu - Tambient)

Solve for Tcpu and you will know the temperature of your processor.

After this, you'll need to run experiments yourself to determine what errors are generated and what correction factors are needed for specific arrangments. Use these correction factors in the appropriate places in the above steps and you will have a very accurate semitheoretical equation that should make everyone on this board (myself included) bow to your l33t skills.

BillA ain't kidding - this is not for the faint of heart.

Alchemy

02-19-2003, 04:39 PM	#7
Alchemy Cooling Savant Join Date: Oct 2002 Location: Boston Posts: 238	Wow. Very ambitious. I like it. I'd go about it this way: 1) Get numerical PQ curves for all the major components - WB, rad, pump - and figure out how to combine the data to determine the pressure drop and flow rate of the system. This might take some iteration for a three-curve problem, but I'm fairly sure it can be done by numerical means. I don't know much programming, but I hope any app you're talking about can run a Newton's method pretty easily. This will solve the flow rate of the system. I'd ignore effects from tubing and take care of them later with a correction factor. You need to run experiments to test these things for at least a few combinations. 2) Get water-side hA-Q diagrams for the radiator and WB, and air-side hA-Q diagrams for the radiator. Input the Q for the water from (1) and the air velocity from whatever fan you're running. You might find it best to have a list of hA values for each fan, since different fans will have different airspeeds depending on the geometry of the radiator. This will generate the heat transfer coefficients (hA) for the WB, water-metal interface in the rad, and metal-air interface in the rad. 3) Solve for the overall heat transfer coefficient UA using the hA coefficients from above: 1/UA = 1/hA (rad-water) + 1/hA (rad-air) + 1/hA (rad-cpu) 4) Using UA from (3), the ambient temperature, and the heat output of the CPU (I'm ignoring the pump here b/c it requires running a couple of the above steps again, probably for minimal benefit). From that you can tell: Heat = UA * (Tcpu - Tambient) Solve for Tcpu and you will know the temperature of your processor. After this, you'll need to run experiments yourself to determine what errors are generated and what correction factors are needed for specific arrangments. Use these correction factors in the appropriate places in the above steps and you will have a very accurate semitheoretical equation that should make everyone on this board (myself included) bow to your l33t skills. BillA ain't kidding - this is not for the faint of heart. Alchemy