Cooler master X dream K640
Posted: Sun Dec 31, 2017 3:30 am
A few months back I lucked into some old CPU heatsinks. I found them in the proverbial University Science department hallway box. I think they are the old iteration of the Cooler Master X Dream K640. I say old because they're copper not aluminum.
The heatsinks in question
They have a luxuriously spacious surface for mounting to (54mm x 67mm).
The fan is a 12V 0.83A and according to the spec sheet it can do 800 ~ 2800 RPM with an airflow of 69.59CFM (Max). The fan however is controlled by a thermistor. I'm not sure how that will factor into using the heatsinks for lights.
Spec sheet:
http://www.coolermaster.com/service/sup ... -KIF-L9E1/
I am hoping to use these heatsinks to build a COB fixture and therefore need to work backwards to figure out what I can reasonably run on them. Since this is a CPU heatsink there does not seem to be a thermal resistance figure available for it from the manufacturer so I've take a stab at figuring it out for myself (please chime in if I have made any errors).
Doing some back of the envelope math (please ignore the volumetric calculations I did before I remembered its not the same thing as surface area) I have broken up the heat sink into four rectangles. A-C being the fins and D the base. It is an awkward thing to measure so where things were tricky I did my best to air on underestimating the measurement.
SA of a rectangular prism = 2ab+2bc+2ac
Fins (fin thickness = 0.33mm)
A. 2(39mm*17mm) + 2(17mm*0.33mm) + 2(39mm*0.33mm) = 1362.96mm2
B. 2(30mm*14mm) + 2(14mm*0.33mm) + 2(30mm*0.33mm) = 869.04mm2
C 2(5mm*19mm) + 2(19mm*0.33mm) + 2(5mm*0.33mm) = 205.84mm2
Total = 1362.96mm + 869.04mm + 205.84mm = 2437.84 * 57 fins = 138956.88mm2
Base
D. 2(54mm*6mm) + 2(6mm*67mm) + 2(67mm*54mm) = 8688mm2
SA fins + base = 138956.88mm + 8688mm = 147644.88mm2
Now using the Bridgelux AN30 Thermal management paper's rule of thumb, 64.5cm2 / 1 hWatt.
Pulling from http://ledgardener.com/find-heat-sink-cob/
147644.88mm2/645mm2/hWatt = 228.9 Watts
Or Growmau5's choosing your heatsink video part 4/7 of 110cm2 for passive or 40cm2 for active.
147644.88mm2/1100mm2/hWatt = 134.22 Watts
147644.88mm2/400mm2/hWatt = 369.11 Watts
These numbers seem to large to me. Where am I going wrong?
The heatsinks in question
They have a luxuriously spacious surface for mounting to (54mm x 67mm).
The fan is a 12V 0.83A and according to the spec sheet it can do 800 ~ 2800 RPM with an airflow of 69.59CFM (Max). The fan however is controlled by a thermistor. I'm not sure how that will factor into using the heatsinks for lights.
Spec sheet:
http://www.coolermaster.com/service/sup ... -KIF-L9E1/
I am hoping to use these heatsinks to build a COB fixture and therefore need to work backwards to figure out what I can reasonably run on them. Since this is a CPU heatsink there does not seem to be a thermal resistance figure available for it from the manufacturer so I've take a stab at figuring it out for myself (please chime in if I have made any errors).
Doing some back of the envelope math (please ignore the volumetric calculations I did before I remembered its not the same thing as surface area) I have broken up the heat sink into four rectangles. A-C being the fins and D the base. It is an awkward thing to measure so where things were tricky I did my best to air on underestimating the measurement.
SA of a rectangular prism = 2ab+2bc+2ac
Fins (fin thickness = 0.33mm)
A. 2(39mm*17mm) + 2(17mm*0.33mm) + 2(39mm*0.33mm) = 1362.96mm2
B. 2(30mm*14mm) + 2(14mm*0.33mm) + 2(30mm*0.33mm) = 869.04mm2
C 2(5mm*19mm) + 2(19mm*0.33mm) + 2(5mm*0.33mm) = 205.84mm2
Total = 1362.96mm + 869.04mm + 205.84mm = 2437.84 * 57 fins = 138956.88mm2
Base
D. 2(54mm*6mm) + 2(6mm*67mm) + 2(67mm*54mm) = 8688mm2
SA fins + base = 138956.88mm + 8688mm = 147644.88mm2
Now using the Bridgelux AN30 Thermal management paper's rule of thumb, 64.5cm2 / 1 hWatt.
Pulling from http://ledgardener.com/find-heat-sink-cob/
147644.88mm2/645mm2/hWatt = 228.9 Watts
Or Growmau5's choosing your heatsink video part 4/7 of 110cm2 for passive or 40cm2 for active.
147644.88mm2/1100mm2/hWatt = 134.22 Watts
147644.88mm2/400mm2/hWatt = 369.11 Watts
These numbers seem to large to me. Where am I going wrong?