Bulk boiling

M5. McEwen, L. H., Batch, J. M., Foley, D. J., and Kreiter, M. R., Heat transfer beyond burnout for forced convection bulk boiling, ASME Paper No. 57-SA-49 (1957). 

Saturated, bulk, boiling is the principal mechanism of interest in the design of reboilers and vaporisers. 

In the bulk boiling section, which appears when the bubble boundary layers have developed so as to fill the core and all of the liquid has reached saturation, there are two important flow patterns bubbly flow and annular flow. In bubbly flow, the bubbles are evenly distributed in the saturated liquid. The superheated... 

The boiling temperature of molten Na is plotted versus the radius of the vapour bubble in Figure 6.15. The boiling temperature is increased by several hundred degrees for a gas bubble with radius 1 pm relative to a flat gas-liquid interface. If the liquid is free of impurities and heterogeneous interfaces, substantial superheating of the liquid above its bulk boiling temperature is possible, as also discussed in Chapter 5. 

Inside a heated duct, the liquid vaporizes in several stages sub-cooled boiling, saturated or bulk boiling, and the dry wall regime. 

When a surface is exposed to a liquid and is maintained at a temperature above the saturation temperature of the liquid, boiling may occur, and the heat flux will depend on the difference in temperature between the surface and the saturation temperature. When the heated surface is submerged below a free surface of liquid, the process is referred to as pool boiling. If the temperature of the liquid is below the saturation temperature, the process is called subcooled, or local, boiling. If the liquid is maintained at saturation temperature, the process is known as saturated, or bulk, boiling. 

FIGURE 11.30 Effect of displaced promoters on CHF for bulk boiling of water. 

Many IPWR designs are neither pure PWRs or pure BWRs, but combine features of both systems as discussed in reference 8 for the specific case of the KWU-NHR 200-MW, district heating reactor. However, BWR-based designs that use bulk boiling are sensitive to coolant density fluctuations and are generally considered unsuitable for mobile applications, such as... 

The second hypothesis (steam fraction) has corroborative evidence from previous work with boiling jets. ° In this earlier work it was found that quasisteady jets underwent a rapid radial expansion after a delay (or residence) period of -0.5-1.0 s. The length of this delay was linked directly to the degree of water subcooling and was apparently tied to the onset of bulk boiling within the... 

Transient Reactor Analysts Code (TRAC) equation of state O for water and steam (obtained by fits to the steam tables) and a stiff gas equation of state for the melt. The constitutive relations required for the interfield coupling terms (heat transfer, momentum exchange, and phase change) include a bulk boiling model, a subcooled surface boiling model, a three-field flow regime map, and adaptations of standard heat transfer and momentum transfer correlations. 

Mass transfer between the water and steam fields is described by a simple bulk boiling model, assuming the existence of an interface between the two fields at the... 

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