2000 Fiscal Year Final Research Report Summary
Study of boiljing phenomena at high heat flues focusing on evaporation in interline region
| Project/Area Number |
10450080
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Thermal engineering
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| Research Institution | University of Tokyo |
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Principal Investigator |
NISHIO Shigefumi The University of Tokyo, Institute of Industrial Science, Professor, 生産技術研究所, 教授 (00111568)
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| Co-Investigator(Kenkyū-buntansha) |
SHIRAKASHI Ryo The University of Tokyo, Institute of Industrial Science, Associate Professor, 生産技術研究所, 助教授 (80292754)
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| Project Period (FY) |
1998 – 2000
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| Keywords | Thermal Engineering / Heat Transfer / Phase Change / Contact-line / Evaporation / Boiling / Critical Heat Flux / Microgroove |
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| Research Abstract |
The present project aimed at obtaining better understanding of the mechanism of phase change at high heat fluxes by combining the following two phase change systems ; a pseudo-two-dimensional boiling system in which information about the relation between bubble structure and contact-line-length density (CLD) is obtained, and a mirogoove evaporation system in which evaporation in the interline region plays an important role in the total heat transfer rate.
The results obtained in the present project are summarized as follows.
(1) The dryout heat flux in the microgroove evaporation system reaches a maximum at a groove width and it is comparable with the critical heat flux (CHF) in pool boiling.
(2) The bubble departure period (BDP) under microgravity conditions can be markedly shortened by using ribbed surface. In addition, the product of CHF and BDP is almost constant and thus shortening of BDP under microgravity conditions results in the increase of CHF.
(3) The dependence of CLD on surface superheat is very similar to the boiling curve. CLD and the number density of dry area on the boiling surface at the critical heat flux (CHF) in saturated boiling are almost independent of the kind of liquid. In particular, the number density of dry area in the large dry-are region is independent of subcooling.
(4) In high heat-flux boiling, liquid-solid contact take the liquid network pattern like canals. The base areas of bubbles are almost dry and liquid-solid contact is localized in the spaces between bubbles. These situations bring about the liquid network pattern at CHF.
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