Hierarchical hydrophilic/hydrophobic micro/nanostructures for pushing the limits of critical heat flux
A high efficiency heat sink for the cooling of microelectronic devices involves a phase change from liquid fluid to fluid vapor with a vapor quality of 100%. The liquid fluid is provided to an active area that contains fins having micrometer dimension that support a membrane that is nanoporous. The membrane is effectively impermeable to liquid fluid but permeable to fluid vapor. The heat sink provides very high heat flux and coefficient of heat transfer at low mass flux over a broad range of surface superheat temperatures. The heat sink can be constructed of equi-spaced posts that separate liquid microchannels from vapor microchannels that are connected through capillary forced valves formed between adjacent equi-spaced posts.
1. A phase change heat sink, comprising:
a reservoir defined by a first surface spaced a distance from a second surface, the reservoir being accessible through a liquid fluid inlet, at least one of the first surface and the second surface comprising a membrane; and
an active area comprising a plurality of solid features extending from a base, the plurality of solid features defining an interstitial space operable to exert capillary forces on a fluid, the active area being accessible through said liquid fluid inlet,
wherein:
a liquid fluid, communicated through the liquid fluid inlet and into the reservoir, is fully vaporized into a vapor fluid in response to absorbing heat; and
said vapor fluid is communicated through said membrane and out of the phase change heat sink, said membrane being permeable to said vaporized vapor fluid and impermeable to said liquid fluid.
2. The phase change heat sink according to claim 1 , wherein said reservoir comprises a liquid microchannel for said liquid fluid and said plurality of solid features extending from said base comprises an array of posts, and wherein said active area includes a vapor microchannel separated from said liquid microchannel by said posts.
3. The phase change heat sink according to claim 1 , wherein said liquid fluid is water.
4. The phase change heat sink according to claim 1 , wherein said liquid fluid is a fluorocarbon or a hydrofluorocarbon.
5. The phase change heat sink according to claim 1 , wherein said plurality of solid features have cross-sections of 1 to 200 micrometers.
6. The phase change heat sink according to claim 1 , wherein said membrane is a hydrophobic membrane.
7. The phase change heat sink according to claim 1 , wherein said membrane is nanoporous or microporous.
8. A method to cool a microelectronic device, comprising:
contacting a microelectronic device to at least one phase change heat sink according to claim 1 ;
providing said liquid fluid to said heat sink;
absorbing heat by vaporizing said liquid fluid to said vapor fluid;
passing said vapor fluid through said membrane of said heat sink;
condensing vapor fluid at a condenser to reform said liquid fluid; and
re-providing said liquid fluid to said heat sink, wherein the vapor quality of said vapor fluid is 100%.
9. The method of claim 8 , wherein said providing is performed with a pump.
10. The method of claim 8 , wherein said vaporizing said liquid fluid to said vapor fluid occurs between a liquid microchannel for said liquid fluid and a vapor microchannel.
11. A phase change heat sink, comprising:
a fluid reservoir defined by a first surface positioned a distance from a second surface, the fluid reservoir being accessible by a liquid fluid through a liquid inlet, at least one of the first surface and the second surface comprising a membrane permeable to a vapor fluid and impermeable to said liquid fluid; and
an active area comprising a plurality of solid features extending from a base, the plurality of solid features dimensioned and configured to exert capillary forces on the liquid fluid,
wherein the liquid fluid is fully vaporized into the vapor fluid in response to the liquid fluid absorbing heat.
12. The phase change heat sink according to claim 11 , wherein said fluid reservoir comprises a liquid microchannel for said liquid fluid and said plurality of solid features extending from the base comprises an array of posts, and wherein said active area includes a vapor microchannel separated from said liquid microchannel by said array of posts.
13. The phase change heat sink according to claim 11 , wherein said liquid fluid is water.
14. The phase change heat sink according to claim 11 , wherein said liquid fluid is an alcohol, a fluorocarbon or a hydrofluorocarbon.
15. The phase change heat sink according to claim 11 , wherein said plurality of solid features have cross-sections of 1 to 200 micrometers.
16. The phase change heat sink according to claim 11 , wherein said membrane is a hydrophobic membrane.
17. The phase change heat sink according to claim 11 , wherein said membrane is nanoporous or microporous.
18. A method to cool a microelectronic device, comprising:
contacting a microelectronic device to at least one phase change heat sink according to claim 11 ;
providing said liquid fluid to said heat sink;
absorbing heat by vaporizing said liquid fluid to said vapor fluid;
passing said vapor fluid through said membrane of said heat sink;
condensing vapor fluid at a condenser to reform said liquid fluid; and
re-providing said liquid fluid to said heat sink, wherein the vapor quality of said vapor fluid is 100%.
19. The method of claim 18 , wherein said providing is performed with a pump.
20. The method of claim 18 , wherein said vaporizing said liquid fluid to said vapor fluid occurs between said fluid reservoir for said liquid fluid and a vapor microchannel.