Isolated bubble region

The heat transfer coefficient was found to be dependent on the existing flow pattern. In the isolated bubble region, lower q effect in confined bubble region, convection dominant in annular-slug region. 

Partial Nucleate Boiling (Isolated Bubble) Region. In this region, heat transfer is often considered to be occurring by three separate mechanisms ... 

It can be seen from the above that, though the principal mechanisms in the partial boiling (isolated bubble) region seemed to have been qualitatively identified, there remain considerable uncertainties about the details of their action under any given set of circumstances and these uncertainties underlie any prediction method based on a mechanistic approach we will return to this point further in the section on predictive models... 

An accepted empirical correlation for the terminal rise velocity of single isolated bubbles is that of Peebles and Garber (1953), who identified four regions as shown in Table 7.1. 

Zuber, N. Nucleate boiling. The region of isolated bubbles and the similarity with natural convection. Int. J. Heat Mass Transfer 6 (1963) 53-78... 

N. Zuber, Nucleate Boiling. The Region of Isolated Bubbles and the Similarity With Natural Convection, Int. J. Heat Mass Transfer (6) 53-78,1963. 

Fig. 7.2. A versatile bubbler manometer. The bubbler manometer Is securely mounted by the reservoir and attached to the vacuum system. It is then easily filled by the following process. The level of the bottom end of the vertical tube dipping into the reservoir is marked on the outside of the reservoir. Next, a calculated amount of mercury is filtered into the reservoir. With the valve between the two arms open, a vacuum is slowly drawn on the manometer. The mercury level must not drop below the mark on the reservoir, or else bubbles will enter the vertical tube and shoot mercury through the vacuum system. If the mercury level in the reservoir comes close to the mark, the manometer is brought up to atmospheric pressure and more mercury is added. When the proper amount of mercury is present in the fully evacuated manometer, the mercury level should be about 10 mm above the mark on the reservoir, and the upper meniscus should be in a region of the manometer suitable for measurement, as illustrated. Once the manometer is properly filled and evacuated, the valve is closed to isolate the reference arm at high vacuum.

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