(A) dry-spot model of critical heat flux and transition boiling in pool and subcooled forced convection boiling = 수조 및 과냉 강제대류비등에서 임계 열유속 및 천이비등을 위한 드라이-스팟 모델

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A new dry-spot model for critical heat flux (CHF) is proposed. The new concept for dry area formation based on Poisson distribution of active nucleation sites and the critical active site number is introduced. The model is based on the boiling phenomena observed in nucleate boiling such as Poisson distribution of active nucleation sites and formation of dry spots on the heating surface. It is hypothesized that when the number of bubbles surrounding one bubble exceeds a critical number, the surrounding bubbles restrict the feed of liquid to the microlayer under the bubble. Then a dry spot of vapor will form on the heated surface. As the surface temperature is raised, more and more bubbles will have a population of surrounding active sites over the critical number. Consequently, the number of the spots will increase and the size of dry areas will increase due to merger of several dry spots. If this trend continues, the number of effective sites for heat transport through the wall will diminish, and CHF and transition boiling occur. The model is applicable to pool and subcooled forced convection boiling conditions, based on the common mechanism that CHF and transition boiling are caused by the accumulation and coalescences of dry spots. It is shown that CHF and heat flux in transition boiling can be determined without any empirical parameter based on information on the boiling parameters such as active site density and bubble diameter, etc., in nucleate boiling. It is also shown that the present model well represents actual phenomena on CHF and transition boiling and explains the mechanism on how parameters such as flow modes (pool or flow) and surface wettability influence CHF and transition boiling. Validation of the present model for CHF and transition boiling is achieved without any tuning parameter always present in earlier models. It is achieved by comparing the predictions of CHF and heat flux in transition boiling using measured boiling parameters in nuc...
Advisors
No, Hee-Cheonresearcher노희천researcher
Description
한국과학기술원 : 원자력공학과,
Publisher
한국과학기술원
Issue Date
1998
Identifier
133589/325007 / 000945466
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 원자력공학과, 1998.2, [ xvi, 180 p. ]

Keywords

Subcooled forced convection boiling; Pool boiling; Transition boiling; Critical heat flux; Nucleate boiling; 핵비등; 과냉강제대류비등; 수조비등; 천이비등; 임계열유속

URI
http://hdl.handle.net/10203/48885
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=133589&flag=dissertation
Appears in Collection
NE-Theses_Ph.D.(박사논문)
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