Boiling, suppression

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.)... 

Experimental results from Chen (1968), Holtz (1971), and Holtz and Singer (1968, 1969) more or less confirmed the validity of Holtz s maximum boiling suppression theory, while some other experimental studies by Deane and Rohsenow (1969), Schultheiss and Smidt (1969) and Kottowski and Grass (1970) did not confirm. This disagreement of experimental results was explained by Dwyer (1976), along with the details of all the experiments. 

Figure 4.13 Boiling suppression factor S [Eq. (4-17)]. (From Chen, 1966. Copyright 1966 by American Chemical Society, Washington, DC. Reprinted with permission.)... 

From Figure 12.57 the nucleate boiling suppression factor, = 0.23... 

Here p, is the pressure scaled by a critical pressure, and the wall roughness Rp was 5 pm. The forced convection heat transfer enhancement factor and boiling suppression factor were used as in [27] ... 

It was supposed, that for a high vapor velocity and a thin liquid film the influence of gravity is small and the correlation for up flow was used. Total boiling suppression occurs when mass quality more than 0.3 for a film thickness less than 60 pm. That value is close to the bubble departure diameter observed for flow boiling in a film. When the film thickness is smaller than the critical one, the forced convection occurs with a small heat transfer coefficient. The crisis of the heat transfer was observed for a complete liquid evaporation on a heated wall. While the mass quality less than 0.3, we have the cell or slug flow mode, so boiling is not suppressed. 

Fig. 5 Boiling in a narrow vertical tube. (A) Boiling suppressed by head, natural convection is shown (B) bubble formation (C) slug formation due to bubble coagulation (D) fully developed slug flow (E) breakdown of slugs at high vapor rates (F) annular-flow-climbing film.

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