Surface for boiling liquids

Abstract

A boiling surface layer is formed on a thermally conductive wall comprising a plurality of ridges separated by grooves provided at microscopic density, with outer sections of the ridges partly deformed into adjacent grooves to provide sub-surface cavities with restricted openings to the outer surface and sub-surface, openings between some of the cavities.

What is claimed is:  .[.1. A thermally conductive metal wall for transferring heat to a boiling liquid in a heat exchange apparatus which comprises a boiling surface layer formed from the wall having a plurality of ridges in said wall separated by grooves provided at microscopic density, with outer sections of said ridges partly deformed into said grooves such that a plurality of sub-surface cavities are formed therein with at least some of said cavities adapted to entrap vapor bubbles to provide boiling nucleation sites, the nucleation site cavities opening to the outer surface of said boiling surface layer through restricted openings having smaller cross-sectional area than the largest cross-sectional area of the cavity interiors with said restricted openings providing communication between the interiors of said cavities and the outer surface of said boiling surface layer for vapor egress; and said grooves and cavities being formed to provide sub-surface openings between at least some adjacent cavities providing fluid communication with the outer surface of said boiling surface layer for liquid ingress to sustain growth of entrapped vapor bubbles as vapor is expelled from said 
     
        restricted openings..]. 2. A thermally conductive wall according to claim .[.1.]. .Iadd.17 .Iaddend.in which said ridges and grooves are parallel to each other.  .[.3. A thermally conductive wall according to claim 1 in which the grooves are provided at density of greater than about 20 grooves 
     
     
        per inch..]. 4. A thermally conductive wall according to claim .[.1.]. .Iadd.17 .Iaddend.in which the grooves are provided at density of greater than about 80 grooves per inch.  .[.5. A thermally conductive wall according to claim 1 in which said ridges are formed by metal displaced from said grooves..].  .[.6. A thermally conductive wall according to claim 1 in which a plurality of second grooves in spaced relation to each other and at microscopic density are superimposed on said ridges in intersecting relation therewith..].  .[.7. A thermally conductive wall according to claim 1 in which a plurality of depressions in spaced relation to each other and at microscopic density are superimposed on said 
     
     
        ridges in intersecting relation therewith..]. 8. A thermally conductive metal wall for transferring heat to a boiling liquid in a heat exchange apparatus which comprises a boiling surface layer formed from the wall having a plurality of ridges in said wall separated by first grooves provided at .[.microscopic.]. density .Iadd.of from about 45 to about 225 grooves per inch .Iaddend.with outer sections of said ridges partly deformed into said first grooves, and a plurality of second depressions in rows spaced from each other provided at .[.microscopic.]. density of .Iadd.from at least about 45 to about 225 depressions per inch .Iaddend.and superimposed on said ridges in intersecting relation therewith, said ridges, first grooves and second depressions being shaped such that a plurality of sub-surface cavities are formed in said first grooves with at least some of said cavities adapted to entrap vapor bubbles to provide boiling nucleation sites, the nucleation site cavities opening to the outer surface of said boiling surface layer through restricted openings having smaller cross-sectional area than the largest cross-sectional area of the cavity interiors with said openings providing communication between the interiors of said cavities and the outer surface of said boiling surface layer for vapor egress, and said first grooves, second depressions and cavities being formed to provide sub-surface openings between .Iadd.said .Iaddend.at least some adjacent cavities providing fluid communication with the outer surface of said boiling surface layer for liquid ingress to sustain growth of entrapped vapor 
     
     
        bubbles as vapor is expelled from said restricted openings. 9. A thermally conductive wall according to claim 8 in which said ridges and first 
     
     
        grooves are parallel to each other. 10. A thermally conductive wall according to claim 8 in which said ridges are formed by metal displaced 
     
     
        from said first grooves and second depressions. 11. A thermally conductive wall according to claim 8 in which said second depressions are grooves 
     
     
        oriented parallel to each other. 12. A thermally conductive wall according to claim 8 in which the depth of said first grooves is greater than the 
     
     
        depth of said second depressions. 13. A thermally conductive wall according to claim 8 formed of aluminum in which said ridges and first grooves are parallel to each other with said ridges formed by metal displaced from said first grooves and second depressions, said second depressions are grooves oriented parallel to each other and 90 degrees from said first grooves, and said first grooves and second depressions are 
     
     
        provided at density of 140- 200 per inch. 14. A thermally conductive wall according to claim 8 in which said ridges and first grooves are parallel to each other, said second depressions are oriented parallel to each other and 90 degrees from said first grooves, and said first grooves are provided at density of .Badd..[.20-120.]..Baddend. .Iadd.45- 120 
     
     
        .Iaddend.per inch. 15. A thermally conductive wall according to claim 8 in which said ridges and first grooves are parallel to each other, said second depressions are parallel to each other and oriented 90 degrees from said first grooves.  .[.16. A thermally conductive metal wall for transferring heat to a boiling liquid in a heat exchange apparatus which comprises a boiling surface layer formed from the wall having a plurality of ridges in said wall separated by grooves provided at density of greater than about 80 grooves per inch, with outer sections of said ridges partially deformed into said grooves such that a plurality of sub-surface cavities are formed therein with at least some of the cavities adapted to entrap vapor bubbles to provide boiling nucleation sites, the nucleation site cavities opening to the outer surface of said boiling surface layer through restricted openings having smaller cross-sectional area than the largest cross-sectional area of the cavity interiors providing communication between the interiors of said cavities and the surface of said boiling surface layer for vapor egress, and said grooves and cavities being formed to provide sub-surface openings between at least some adjacent cavities for communication between the interiors of said adjacent cavities and the outer surface of said boiling surface layer for liquid ingress to sustain growth of entrapped vapor bubbles as vapor is expelled 
     
     
        from said restricted openings..]. 17. A thermally conductive metal wall for transferring heat to a boiling liquid in a heat exchange apparatus which comprises a boiling surface layer formed from the wall having a plurality of ridges in said wall separated by first grooves with outer sections of said ridges partially deformed into said first grooves, and a plurality of second grooves superimposed on said ridges at an angle to the orientation of said ridges, said ridges and first and second grooves being shaped such that a plurality of sub-surface cavities are formed in said first grooves with at least some of the cavities adapted to entrap vapor bubbles to provide boiling nucleation sites, the nucleation site cavities opening to the outer surface of said boiling surface layer through restricted openings having smaller cross-sectional areas than the largest cross-sectional area of the cavity interiors providing communication between the interiors of said cavities and the surface of said boiling surface layer for vapor egress, and said first and second grooves and cavities being formed to provide sub-surface openings between .Iadd.said .Iaddend.at least some adjacent cavities for communication between the interiors of said adjacent cavities and the outer surface of said boiling surface layer for liquid ingress to sustain growth of entrapped vapor bubbles as vapor is expelled from said restricted openings .Iadd., with said first and second grooves each provided at density of from about 45 to about 225 grooves per inch.Iaddend..  .[.18. A thermally conductive metal wall for transferring heat to a boiling liquid in a heat exchange apparatus which comprises a boiling surface layer having a pluraity of ridges separated by grooves provided at microscopic density with said ridges shaped to form a plurality of sub-surface cavities with at least some of said cavities adapted to entrap vapor bubbles and constitute boiling nucleation sites, the nucleation site cavities communicating with the outer surface of said boiling layer through restricted openings between outer sections of said ridges and having smaller cross-sectional area than the largest cross-sectional area of the cavity interiors for vapor egress, and said grooves and cavities being formed to provide sub-surface openings between at least some adjacent cavities providing fluid communication with the outer surface of said boiling surface layer for liquid ingress to sustain growth of entrapped vapor bubbles as vapor 
     
     
        is expelled from said restricted openings..]. 19. A thermally conductive wall according to claim .[.18.]. .Iadd.17 .Iaddend.in which the limiting dimension of said restricted openings is less than about 5 mils.  .[.20. A thermally conductive wall according to claim 1 in which the limiting 
     
     
        dimension of said restricted opening is less than about 5 mils..]. 21. A thermally conductive wall according to claim 8 in which the limiting 
     
     
        dimension of said restricted openings is less than about 5 mils. 22. A thermally conductive wall according to claim 8 in which said ridges and first grooves are parallel to each other with said ridges formed by metal displaced from said first grooves and second depressions, said second depressions are grooves oriented parallel to each other, said first grooves and second depressions are provided at density of 140- 200 per inch, and in which the limiting dimension of said restricted openings is 
     
     
        less than 1.75 mils. 23. A thermally conductive wall according to claim 8 in which said ridges and first grooves are parallel to each other, said second depressions are oriented parallel to each other, said first grooves are provided at density of 45- 120 per inch, and in which the limiting dimension of said restricted openings is 1.75- 4 mils.