a recent article from thermal engineering company advanced thermal solutions, inc. (ats) examined the thermal performance of both macrochannel and microchannel liquid cold plates in the cooling of electronics.
the article examines the thermal performance of microchannel cold plates.
(advanced thermal solutions, inc.)
the article gave equations for measuring the thermal performance of cold plates, but was mostly focused on the increased use in microchannels and the higher thermal performance that can be achieved using that type of cold plate in a liquid cooling system.
it also discusses an approach referred to as force-fed boiling (ffb). the example used in the article included a micro-grooved copper surface with alternating fins and channels.
“there are feed channels on top of the micro-grooved surface,” the article explained. “the fluid is forced through these channels into the microgrooves, which are located on top of the heated surface. the fluid vaporizes in the microgrooves and moves upward, while the liquid flows beneath the escaping vapor. this keeps the surface wet, resulting in an increase of the critical heat flux (chf).”
as noted in the article, for heat fluxes of 200 w/cm2 or less heat transfer is independent of the flow rate of the fluid running through a cold plate, but this is different at higher heat fluxes. the slop of the heat flux decreases as temperature increases.
in addition, “at first, the heat transfer coefficient increases with the increase in heat flux. this indicates that by increasing the heat flux, a phase change process takes place which changes the single-phase flow to two-phase heat transfer. after reaching an impressive peak at 300 kw/m2k, the heat transfer coefficient starts to decrease. this is attributed to local dryouts from bubble generation, which also blocks the microchannels.”
the article concluded, “while advances in cold plate performance have been incremental, their technology is still evolving. improvements in microchannel manufacturing will open more opportunities in this field. microchannel cold plates provide tremendous heat transfer coefficient capacities, but limitations prevent their broad deployment.”