Cavities boiling

Wall superheat reductions up to a factor of 10 have been reported with some of these surfaces. It should be noted that the mechanism of vaporization for these surfaces is different from that for normal cavity boiling. Here the liquid flows via selected paths or channels to the interior, where thin-film evaporation occurs over a large surface area the vapor is then ejected through other paths by bubbling [38,39]. It should be emphasized that the performance of these special surfaces is quite sensitive to surface geometry and fluid condition. Additionally, very low temperature differences are involved hence, it is necessary to be especially careful, or at least consistent, in measuring wall temperatures and saturation temperatures (pressures). The first comprehensive comparison of the nucleate boiling performances... 

The cavities are filled with the crystal water of the zeolite, which can be driven off by heating the name zeolite means boiling stone. In the empty cavities of the dehydrated molecular sieve other molecules can now be included, provided that their effective cross-section is not larger than the pore diameter of the zeolite. 

Sato and Matsumura (1964), and Bergles and Rohsenow (1964) have proposed the equation for the incipient boiling condition in the case that surface cavities of all sizes are available for nucleation. Hino and Ueda (1985) studied incipient boiling of fluorocarbon R-113 in a stainless steel tube of d = 1 mm at mass velocity G = 158—1,600 kg/m s, and inlet subcooling ATsub,m = 7s — Tin ranged from 10-... 

K. In the case where the upper limit of available cavity sizes was restricted to radius the incipient boiling condition was expressed as follows by Hino and Ueda(1985) ... 

Part 1 Boiling characteristics. Int J Multiphase Flow 11 269-281 Hsu YY (1962) On size range of active nucleation cavities on a heating surface. J Heat Transfer 84 207-216... 

Klein D, Hetsroni G, Mosyak A (2005) Heat transfer characteristics of water and APG surfactant solution in a micro-channel heat sink. Int J Multiphase Flow 31 393 15 Kosar, A, Kuo, CJ, Peles, Y (2005) Boiling heat transfer with reentrant cavities. Int. J. Heat Mass Transfer 48 4867-4886... 

Figure 2.5 Idealized representation of an active cavity (a) situation at maximum boiling suppression (b) situation at incipient boiling. (From Dwyer, 1976. Copyright 1976 by American Nuclear Society, LaGrange Park, IL. Reprinted with permission.)... 

Equation (2-113) means that any cylindrical cavity for any liquid-solid combination under a given pressure has a minimum heat flux below which boiling will not be stable, and a transition between natural convection and stable nucleate boiling (bumping) is always observed. 

Figure 2.26 Heat transfer characteristics for stable nucleate boiling of sodium on a polished, flat, horizontal, nickel plate containing a single cylindrical artificial cavity. (From Deane Rohsenow, 1969. Copyright 1969 by American Society of Mechanical Engineers, New York. Reprinted with permission.)...

Schultheiss (1970) also investigated experimentally the incipient boiling superheat of sodium in wall cavities with sodium oxide concentration as one of the... 

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