isofilm

Hi All,

We have a new online forced convection heat sink calculator (as well as other thermal calculators), that may be of interest to you and your readers.

Let me know how you like these calculators, and what improvements or additions you would like to see.

Best regards,
Daniel L. Thomas
Chief Technology Officer
Novel Concepts, Inc.
11752 Feinberg Place
Las Vegas, NV 89138
702 363 8443 – Direct
dt@novelconceptsinc.com
http://www.novelconceptsinc.com

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isofilm

We have noticed users inputting heat sinks the size of football fields, with flow rates approaching NASA’s wind tunnel.

So we are offering these quick notes (a lesson in English to Metric conversion):

Volumetric Flow Rate – 1 cubic meter per second (m^3/s) = 2,118.88 cubic feet per minute (CFM), that means that a typical computer fan delivering 25 CFM equates to 0.0118 m^3/s.

Number of Fins – This is pretty obvious, just remember that the number of fins times fin width, must be less than the heat sink width.

Fin Width – 1 meter (m) = 39.37 inches (in.), thus a typical high density folded fin width of 0.010 inches (10 mils) equals 0.000254 meters, and equals 254 microns.

Fin Length – Again, given 1 meter (m) = 39.37 inches (in.), and that a typical microprocessor heat sink is around 80 millimeters (3.15 in.), this equals 0.08 meter.

Fin Height – Finally, with fin heights between 1 and 2 inches, which equals 25.4 to 50.8 millimeters (mm), and also equals 0.0254 to 0.0508 meters.

Thermal Conductivity – 1 Watt per meter Kelvin (W/mK), which comes from 1 Watt per square meter Kelvin per meter (W/m^2K/m), means that 1 watt will flow (transfer) through 1 square meter of material, 1 meter thick, with a 1 degree Kelvin temperature differential across opposing faces. 1 W/mK = 6.938 BTU-in./hr-ft^2-F. At 25C, aluminum (pure) has a thermal conductivity of 238 W/mK, and copper (pure) is 401 W/mK, diamond (type iia) is 2,300.

Thermal Resistance – 1 degree Celsius per watt (C/W) means that the heat input surface will increase 1 degree Celsius for each watt of input power.

Pressure Drop – 1 atmosphere (at sea level) equals 101,325 Pascal, and also equals 407.2 inches of water. A typical computer fan provides around 0.1 inches of water pressure, which equals 24.88 Pascal.

Example: Find the optimum number of fins and fin thermal resistance for a copper heat sink, where the heat sink width is 0.08m (80mm), the fin height is 0.04m (40mm), the fin width is 0.00025m (0.25mm), and where the fan can deliver 50 Pascal (0.2 in. of water) at a flow rate of 0.01 m^3/s (21.2 CFM).

Answer – 65 fins will have a thermal resistance of 0.154 C/W.

Remember to add the heat sink base thermal resistance by using our Slab Thermal Resistance with Constriction calculator.

Best regards,
Daniel L. Thomas
Chief Technology Officer
Novel Concepts, Inc.
11752 Feinberg Place
Las Vegas, NV 89138
702 363 8443 – Direct
dt@novelconceptsinc.com
http://www.novelconceptsinc.com

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jmke

thank you for the clarifications Daniel; I was a bit confused at the beginning too with the multitude of options. This Calculator will prove very useful for those into DIY heatsink creation

or to get an idea how their heatsink will perform with different fans

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Sidney

And, more importantly it is more science than personal feeling in dealing with thermal management.

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lazyman

Opteron 165 (2) @2.85 1.42 vcore AMD Stock HSF + Chill Vent II