E,9 • NUCLEATE BOILING 



Because of the observed effect of activity on heat transfer, however, it is 

 possible to make quahtative predictions for the effect of some of the 

 variables on boiling heat transfer. The factors discussed below, which 

 lead to increased bubble activity, should also lead to improved heat trans- 

 fer. This view may be kept in mind when examining the experimental 

 data that follow. 



Experimental Results. 



Heat transfer. Having considered a number of the factors which may 

 influence nucleate boiling, some experimental results as well as references 

 for additional data will be given. A considerable amount of information 



40 80 120 160 



Saturation temperature - 



200 240 280 320 



liquid temperature. 



Fig. E9f. Heat transfer vs. subcooling. Distilled degassed water. 

 Pressure range from 15 Ib/in.^ abs to 164 Ib/in.^ abs [67]. 



on water can be found in [66,67,78]. Some results from [67] on the burnout 

 points for distilled degassed water at various velocities are reproduced in 

 Fig. E,9f. 



The extremely high heat transfer rates observed in some of these tests 

 are certainly noteworthy. Data on burnout points with free convection 

 for distilled water, distilled carbon tetrachloride, a water-aerosol solution, 

 as well as aerated water, are shown in Fig. E,9g and E,9h [64\. An attempt 

 may be made to give some explanation for the shape and relative position 

 of these curves. 



The increase in heat transfer with decreasing temperature is probably 

 caused principally by the increase in the temperature differential itself. 

 The reason that the water-aerosol data is below that for distilled water 

 may be traced to the difference in surface tension. Lower surface tension 



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