A Theoretical Model to Predict Pool Boiling CHF Incorporating Effects of Contact Angle and Orientation

2001 ◽  
Vol 123 (6) ◽  
pp. 1071-1079 ◽  
Author(s):  
Satish G. Kandlikar
Keyword(s):  
Contact Angle ◽  
Theoretical Model ◽  
Pool Boiling ◽  
Heater Surface ◽  
Hydrodynamic Behavior ◽  
Cryogenic Liquids ◽  
Receding Contact ◽  
Surface Liquid ◽  
Receding Contact Angle ◽  
Theoretical Considerations

A theoretical model is developed to describe the hydrodynamic behavior of the vapor-liquid interface of a bubble at the heater surface leading to the initiation of critical heat flux (CHF) condition. The momentum flux resulting from evaporation at the bubble base is identified to be an important parameter. A model based on theoretical considerations is developed for upward-facing surfaces with orientations of 0 deg (horizontal) to 90 deg (vertical). It includes the surface-liquid interaction effects through the dynamic receding contact angle. The CHF in pool boiling for water, refrigerants and cryogenic liquids is correctly predicted by the model, and the parametric trends of CHF with dynamic receding contact angle and subcooling are also well represented.

The Effects of Asymmetric Micro Ratchets on Dynamic Contact Angle and Pool Boiling Performance

2012 ◽  
Author(s):  
Lance Austin Brumfield ◽  
Sunggook Park
Keyword(s):  
Contact Angle ◽  
High Speed ◽  
Pool Boiling ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angles ◽  
Equilibrium Contact Angle ◽  
Droplet Impingement ◽  
Receding Contact ◽  
Receding Contact Angle

The dynamic advancing and receding contact angles of 5μl water droplets were experimentally measured via the droplet impingement technique on a polished brass surface, one brass symmetric micro ratchet, and five brass asymmetric micro ratchet samples of varying dimensions. Droplets were released from varying heights (Weber number) and the impacts studied via high speed camera. Equilibrium advancing and receding contact angles were measured by placing a water droplet on the surfaces and tilting it. Contact angle values were then compared to an existing pool boiling model which incorporates the dynamic receding contact angle, surface roughness ratio, and equilibrium contact angle.

The Surface Modification with Fluorocarbon Thin Films for the Prevention of Stiction in Mems

1998 ◽  
Vol 518 ◽  
Author(s):  
Sang-Ho Lee ◽  
Myong-Jong Kwon ◽  
Jin-Goo Park ◽  
Yong-Kweon Kim ◽  
Hyung-Jae Shin
Keyword(s):  
Contact Angle ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Fluorocarbon Films ◽  
Perfluorodecanoic Acid ◽  
Large Hysteresis ◽  
Static Contact ◽  
Receding Contact ◽  
Highly Hydrophobic ◽  
Receding Contact Angle

AbstractHighly hydrophobic fluorocarbon films were prepared by the vapor phase (VP) deposition method in a vacuum chamber using both liquid (3M's FC40, FC722) and solid sources (perfluorodecanoic acid (CF3(CF2)8COOH), perfluorododecane (C12F26)) on Al, Si and oxide coated wafers. The highest static contact angles of water were measured on films deposited on aluminum substrate. But relatively lower contact angles were obtained on the films on Si and oxide wafers. The advancing and receding contact angle analysis using a captive drop method showed a large contact angle hysteresis (ΔH) on the VP deposited fluorocarbon films. AFM study showed poor film coverage on the surface with large hysteresis. FTIR-ATR analysis positively revealed the stretching band of CF2 groups on the VP deposited substrates. The thermal stability of films was measured at 150°C in air and nitrogen atmospheres as a function of time. The rapid decrease of contact angles was observed on VP deposited FC and PFDA films in air. However, no decrease of contact angle on them was observed in N2.

The effect of contact line dynamics and drop formation on measured values of receding contact angle at very low capillary numbers

2012 ◽  
Vol 404 ◽  
pp. 63-69 ◽  
Author(s):  
Carmen L. Moraila-Martínez ◽  
Francisco J. Montes Ruiz-Cabello ◽  
Miguel A. Cabrerizo-Vílchez ◽  
Miguel A. Rodríguez-Valverde
Keyword(s):  
Contact Angle ◽  
Contact Line ◽  
Drop Formation ◽  
Receding Contact ◽  
Receding Contact Angle ◽  
Contact Line Dynamics

Measurement of dynamic/advancing/receding contact angle by video‐enhanced sessile drop tensiometry

1996 ◽  
Vol 67 (8) ◽  
pp. 2852-2858 ◽  
Author(s):  
Shi‐Yow Lin ◽  
Hong‐Chi Chang ◽  
Lung‐Wei Lin ◽  
Pao‐Yao Huang
Keyword(s):  
Contact Angle ◽  
Sessile Drop ◽  
Receding Contact ◽  
Receding Contact Angle

Determination of the Receding Contact Angle of Sessile Drops on Polymer Surfaces by Evaporation

Langmuir ◽  
1999 ◽  
Vol 15 (21) ◽  
pp. 7378-7385 ◽  
Author(s):  
H. Yildirim Erbil ◽  
G. McHale ◽  
S. M. Rowan ◽  
M. I. Newton
Keyword(s):  
Contact Angle ◽  
Polymer Surfaces ◽  
Receding Contact ◽  
Receding Contact Angle ◽  
Sessile Drops

On the Uniqueness of the Receding Contact Angle: Effects of Substrate Roughness and Humidity on Evaporation of Water Drops

Langmuir ◽  
2014 ◽  
Vol 30 (31) ◽  
pp. 9346-9354 ◽  
Author(s):  
Paola G. Pittoni ◽  
Chia-Hui Lin ◽  
Teng-Shiang Yu ◽  
Shi-Yow Lin
Keyword(s):  
Contact Angle ◽  
Substrate Roughness ◽  
Receding Contact ◽  
Water Drops ◽  
Receding Contact Angle

Heterogeneous Nucleation With Artificial Cavities

2005 ◽  
Vol 127 (11) ◽  
pp. 1189-1196 ◽  
Author(s):  
Yusen Qi ◽  
James F. Klausner
Keyword(s):  
Contact Angle ◽  
Heterogeneous Nucleation ◽  
Deterministic Model ◽  
Contact Angle Hysteresis ◽  
Pool Boiling ◽  
Experimental Results ◽  
Bulk Fluid ◽  
Cylindrical Cavities ◽  
The Difference ◽  
Theoretical Considerations

Bubble incipience in artificial cavities manufactured from silicon has been studied using gas nucleation and pool boiling. Moderately wetting water and highly wetting ethanol have both been used as the bulk fluid with cylindrical cavities, as well as those with a triangle, square, and rectangle shape cross section. Nominal cavity sizes range from 8to60μm. The incipience conditions observed for water using both gas nucleation and pool boiling suggest that bubble initiation originates from a concave meniscus. Cornwell’s contact angle hysteresis theory for vapor-trapping cavities is used to explain the gas nucleation results. The pool boiling results are more difficult to explain. Using ethanol, cavities appeared to be completely flooded and were not activated using either gas nucleation or pool boiling. Using water and gas nucleation, cavities were almost always activated, provided the incipience criterion was satisfied; in contrast cavities in pool boiling with water activated with different superheats during different experiments. The difference in incipience behavior between gas nucleation and pool boiling with water is explained based on vapor-trapping and thermal suppression considerations. Based on limited experimental results, it appears that the backpressure does not influence gas bubble incipience, provided the pressure difference is the same. The experimental results presented affirm the theory of heterogeneous nucleation from vapor-trapping cavities provided contact angle hysteresis and vapor trapping are fully accounted for. However, the results also suggest that the theoretical considerations required for a deterministic model for incipience from vapor-trapping cavities during boiling is more complex than previously hypothesized.

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