Originally Posted by Mindchi|l
I've never been happy with any direct die block I've designed for a cpu because heat only seems to move in a ~ 40-50mm circumference around the heat source (cores). I'm sure this is a main reason waterblock designers engineer blocks that concentrate on this area. As you move away from that circumference the block moves less and less heat ouside that area.
I've had dual tec blocks that read -10c on the ends and 20c in the middle. I've found a dual tec chiller will move more heat because heat transfer is dristributed equally across the whole tec.
This is the main reason I just don't make dual tec blocks. I think the only way to actually get a dual tec block to work properly is using heat pipes to move the heat away from the cores.
I totally understand your concern. Actually I have done some rough simulations to calculate the optimal cold plate thickness. You readings of -10c at end and 20c in the middle is close to my simulation result.
I have a question, What size (thickness) of cold plate did you use in that test?
Here is the simulated temperature distribution across the center line on the top of 10cm by 5cm cold plates (400W cpu power). Note that all temperature is relative
, so only take the dT reading.
Graph for 10mm:
As the cold plate gets thicker, the temperature at the cold side of TEC gets more uniform. But thicker means larger value of C/W value from CPU to TEC, too. The optimal thickness is between between 8-12mm. Certainly this aspect affects the performance of the block. But overall it's not too bad because in the center the hotter area compensates the lost heat transferring across TECs at the two ends, as Qmax is a semi-linear function of temperature.
Yeah, heat pipes will help. I bet you have though about a sandwiched version of direct die block, which the water block is in the middle and on the top and bottom there are two TECs with cold plates linked by heatpipes. I like chillers, with their ever expanding Qmax. Adding more TECs easily fixes the efficiency problem. My only concern is the complexity of two loops and insulation issues.