Just a point of information- it is actually a hot heatsink that will be the most "efficient" heatsink (the only other qualification being that "hot" should not exceed what the CPU can tolerate while functioning normally). The hotter the heatsink ends up, the great the temperature differential between that and ambient air, and thus the most heat transfer will occur for a given air flow rate. A hotter core temp also gives the benefit of having more T's to drive heat to the extreme physical dimensions of the heatsink, thus making more of the heatsink effective. This could also be applied in a perverse sense with a relatively "warm" heatsink except you blow artificially cooled air unto it to give a similar temperature differential as the original case.
WRT to a non-vertical heatpipe scenario- isn't there some sort of wicking material in the core of the heatpipe? I remember vaguely that this wick enables capillary action to move vapor and fluid in the intended direction. So this allows the heatpipe to still operate in horizontal configurations (albeit, still not as well as in the optimal orientation). I'm pulling this from memory, so I could be wrong on this, though.
The first is a tube containing a liquid. The liquid is chosen for its evaporation point, so that it is fluid at room temp, but evaps at the temp of the cpu. It is in the tube under a partial vacuum. When the liquid heats up ( sitting at the bottom of the tube ) it evaporates and moves to the top of the tube, where the heatsink convects the heat, and the gas condenses. It then flows down the tube to the cpu.
Obviously this is gravity dependant, and not too handy ( has useful applications ).
The second type of heat pipe adds a wicking material to the inside of the tube. The wicking material holds the liquid. Both ends now have fluid available for evaporation ( as does the middle ). When the fluid evaporates it leaves the wick, which, through capillary action draws fluid towards the heat source.
These heat pipes work upside down and back to front.
I think it is fair assume the apple uses them ( they already use them for laptops ) as heatpipes that are bent really need to have wicks ( even having a non wicked hp off of vertical reduces its efficiency ).
A good heatpipe has a temperature differential of less than one degree c between each end.
In the world of heat sinks, heatpipes are the only way to efficiently distribute heat to the ends of large heatsinks.
Comments
WRT to a non-vertical heatpipe scenario- isn't there some sort of wicking material in the core of the heatpipe? I remember vaguely that this wick enables capillary action to move vapor and fluid in the intended direction. So this allows the heatpipe to still operate in horizontal configurations (albeit, still not as well as in the optimal orientation). I'm pulling this from memory, so I could be wrong on this, though.
The first is a tube containing a liquid. The liquid is chosen for its evaporation point, so that it is fluid at room temp, but evaps at the temp of the cpu. It is in the tube under a partial vacuum. When the liquid heats up ( sitting at the bottom of the tube ) it evaporates and moves to the top of the tube, where the heatsink convects the heat, and the gas condenses. It then flows down the tube to the cpu.
Obviously this is gravity dependant, and not too handy ( has useful applications ).
The second type of heat pipe adds a wicking material to the inside of the tube. The wicking material holds the liquid. Both ends now have fluid available for evaporation ( as does the middle ). When the fluid evaporates it leaves the wick, which, through capillary action draws fluid towards the heat source.
These heat pipes work upside down and back to front.
I think it is fair assume the apple uses them ( they already use them for laptops ) as heatpipes that are bent really need to have wicks ( even having a non wicked hp off of vertical reduces its efficiency ).
A good heatpipe has a temperature differential of less than one degree c between each end.
In the world of heat sinks, heatpipes are the only way to efficiently distribute heat to the ends of large heatsinks.
Originally posted by mark_wilkins
Do you mean "laminar?"
Don't mean to be pedantic, just wondering if you meant something other than what I thought you did.
-- Mark
Sorry typo error ; it's laminar.