LittleDevil, sorry no updates really, I'm waiting on some material.

Quote Originally Posted by johann
Why is the cartridge so far away from the surface?

I think also the big mass of that block is not the best.
That's a good question Johann, basically I want the most distance I can get within the block so that the heat flux has a good chance to even out over the surface of the contact face. I think a CPU probably has a very uniform distribution of heat generation over it's surface, so I want to create a uniform distribution of heat flux (flow).

The problem is very similar to a fluid flow problem. If you want uniform fluid velocities over the cross section of a pipe, as long as it's turbulent flow, you need a long length of straight pipe to let the eddys entance effects dissipate.

For this block I will not be able to measure the heat flux distribution, but I'm using what I would call engineering judgement. A longer length, and more mass will not affect at all the amount of energy delivered to the contact face if all other surfaces are well insulated. If the energy has no other path by which to escape...it will flow down the only path.

I did a rough analysis in which I calculated the time required just to cool this block down, something like 61 seconds assuming the evap has a capacity of 200W, but during a pull down, the evap capacity is way higher, so I'd estimate 30 seconds to cool the block from ambient to -40C.

I figure a single evap test may take 1 hour of tweaking and stabilizing to achieve the conditions, so the mass of the block has no effect on it's function as a load tester