On the hot-spot-controlled critical heat flux mechanism in saturated pool boiling. Part II. The influence of contact angle and nucleation site density

Journal Article · Sun Aug 01 00:00:00 EDT 1993 · Journal of Heat Transfer (Transactions of the ASME (American Society of Mechanical Engineers), Series C); (United States)

DOI:https://doi.org/10.1115/1.2910763· OSTI ID:7113775

Unal, C; Sadasivan, P; Nelson, R A ^[1]

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1. Los Alamos National Lab., NM (United States)

The first objective of this note is to investigate a lack of a second transition region within the framework of the hot-spot model. The second objective of this note is to test the hot-spot hypothesis further for the lower contact angle to confirm the functional variation of the critical rewetting temperature with the contact angle. We use a two-dimensional cylindrical-coordinate transient conduction model to study the saturated pool nucleate boiling phenomenon in the second transition region on a horizontal surface. We have examined the lack of a second transition boiling region in the experiments of Wang and Dhir. In addition to the original requirements of a thick heater with high thermal conductivity for observing the second transition boiling region presented by Unal et al. (1922a), an additional criterion determined here is that the active nucleation site density must not be too high. This new requirement should be included in the experimental efforts originally suggested and aimed at investigating the hot-spot hypothesis. It also indicates that the lack of existence of the second transition region on the boiling curve does not necessarily indicate the lack of significant heater surface dryout as we had suggested earlier. Calculations based on the data of Wang and Dhir (1991) showed that the surface temperatures on the wet regions are very low due to their high nucleation site density. This suggests that dry patches must exist on their heater, so that the surface-averaged temperatures would be as measured in their experiments. 8 refs., 2 figs., 2 tabs.

• OSTI ID: 7113775
• Journal Information: Journal of Heat Transfer (Transactions of the ASME (American Society of Mechanical Engineers), Series C); (United States), Vol. 115:3; ISSN 0022-1481
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
POOL BOILING
CRITICAL HEAT FLUX
HEAT TRANSFER
EVAPORATION
HOT SPOTS
MATHEMATICAL MODELS
NUCLEATION
THEORETICAL DATA
BOILING
DATA
ENERGY TRANSFER
HEAT FLUX
INFORMATION
NUMERICAL DATA
PHASE TRANSFORMATIONS
420400* - Engineering- Heat Transfer & Fluid Flow
990200 - Mathematics & Computers