Pool boiling curve

Figure 12.54. Typical pool boiling curve (water at 1 bar)...

Westwater, J. W., J. C. Zinn, and K. J. Brobeck, 1989, Correlation of Pool Boiling Curves for the Nomo-logous Group—Freons, Trans. ASME, J. Heat Transfer 111 204-207. (2)... 

FIGURE 15.32 Pool boiling curves for wall-temperature-controlled and heat-flux-controlled systems (from Hewitt et al. [13], with permission. Copyright CRC press, Boca Raton, FL). 

FIGURE 15.33 Pool-boiling curves obtained under transient heating and cooling compared with pool-boiling curve obtained for steady state (boiling of Fluorinert FC-72) (from Blum et al. [72], with permission). 

FIGURE 15.42 Pool-boiling curves for the boiling of refrigerant 113 at zero gravity compared with values predicted for normal gravity. Experiments carried out in space shuttle (from Lee and Merte [85] with permission). 

FIGURE 15.68 Effect of pressure on the pool-boiling curve for water on a copper surface (from Pan and Lin [181 ], with permission from Elsevier Science). 

Figure 15.92 shows data (plotted in the form of the boiling curve, i.e., as heat flux versus wall superheat) for fixed subcooling at various velocities. For this particular set of data, the results at the lowest velocity agreed well with a pool-boiling curve obtained for the same... 

H. S. Lee and H. Merte, The Pool Boiling Curve in Microgravity, in 34th Aerospace Sciences Meeting Exhibit, Reno, NV, Paper A1AA 96-0499, January 1996. 

Figure 7-11 Pool boiling curve for water at atmospheric pressure.

In Figure 22.21 a pool boiling curve shown where the applied heat flux is plotted versus the temperature difference (AT = Tg- between the surface temperature and the liquid saturation temperature. 

Fig. 2. Boiling curve of a heat-flux-controlled surface with pool boiling.

Nukiyama was unable to establish a condition on the line CD, and in his original experimental curves he shows this line dotted. However, Farber and Scorah (F2) have reported that with special surface treatment and very careful experimentation, quasistable conditions can be set up on a curve such as CD in pool boiling. Their procedure was to first reach point D by way of ACFD and then to very carefully increase the heat flux. However, any disturbance or sudden change of heat flux when in the region CD caused the system to revert to the stable regions GC or DF. 

Figure 2.41 Curves illustrating the effect of surface wetting on pool boiling heat transfer (a) heat flux versus (/ . - rsa() (b) heat flux versus heat transfer coefficient. (From Dwyer, 1976. Copyright 1976 by American Nuclear Society, LaGrange Park, IL. Reprinted with permission.)...

FIGURE 1L5 Pool boiling from smooth and structured surfaces on the same apparatus [40]. (a) sketch of cross sections of three enhanced heat transfer surfaces tested (b) boiling curves for three enhanced tubes and smooth tube. 

The use of structured surfaces to enhance thin-film evaporation has also been considered recently. Here, in contrast to the flooded-pool experiments noted above, the liquid to be vaporized is sprayed or dripped onto heated horizontal tubes to form a thin film. If the available temperature difference is modest, structured surfaces can be used to promote boiling in the film, thus improving the overall heat transfer coefficient. Chyu et al. [43] found that sintered surfaces yielded nucleate boiling curves similar to those obtained in pool boiling. T-shaped fins did not exhibit low AT boiling however, a threefold convective enhancement was obtained as a result of the increased surface area. 

The enhanced convection provided by stirring dramatically improves pool boiling at low superheat. However, once nucleate boiling is fully established, the influence of the improved circulation is small. Pramuk and Westwater [255] found that the boiling curve for methanol was favorably altered for nucleate, transition, and film boiling, with the improvement increasing as agitator speed increased. 

Many applications of pool boiling are transient in nature. Careful experiments on transients in which the wall temperature is either increased or decreased with time are reported by Blum et al. [72] the results are shown in Fig. 15.33. As will be seen, the boiling curve under transiently changing wall temperature conditions can differ significantly with both the rate of change and the direction of change. These results typify the many unknowns and uncertainties in the pool-boiling process, and the reader should be aware of these from the outset ... 

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