Boiling crisis

A4. Aladyev, I. T., Miropolsky, Z. L., Doroshchuk, V. E., and Styrikovitch, M. A., Boiling crisis in tubes, Intern. Heat Transfer Conf, Boulder, Colorado, 1961, paper No. 28, 237. 

Physical Mechanisms of Flow Boiling Crisis in Visual Observations 304... 

This is an engineering textbook, and it aims to improve the performance of boiling equipment. Hence, it emphasizes the boiling crisis and flow instability. The first five chapters, besides being important in their own right, serve as preparation for understanding boiling crisis and flow instability. 

Ruddick (1953) and Lowdermilk et al. (1958) found that flow oscillation can induce a premature boiling crisis. Moreover, in a boiling water reactor the flow oscillation may induce a nuclear instability. Thus, in designing a boiling system, it is imperative to predict and prevent those operational conditions that might create flow oscillation. 

Because the bubble population increases with heat flux, a point of peak flux may be reached in nucleate boiling where the outgoing bubbles jam the path of the incoming liquid. This phenomenon can be analyzed by the criterion of a Hemholtz instability (Zuber, 1958) and thus serves to predict the incipience of the boiling crisis (to be discussed in Sec. 2.4.4). Another hydrodynamic aspect of the boiling crisis, the incipience of stable film boiling, may be analyzed from the criterion for a Taylor instability (Zuber, 1961). 

Effects of experimental parameters on pool boiling crisis with ordinary liquids In the... 

Effects of experimental parameters of pool boiling crisis with liquid metals... 

It should be noted that without experimental data on the subcooled pool boiling crisis in liquid metals, the above equation cannot be verified. Another mechanism for estimating the subcooling contribution to the CHF was used for boiling with ordinary liquids (i.e., a conduction mechanism). The two mechanisms may operate simultaneously, along with the hydrodynamics and conduction-convection mechanisms (Dwyer, 1976). 

Phase 1 To understand the mechanisms of flow boiling crisis by means of... 

Visual study of boiling crisis in various flow patterns Microscopic analysis of boiling crisis in each known flow pattern... 

PHYSICAL MECHANISMS OF FLOW BOILING CRISIS IN VISUAL OBSERVATIONS... 

To understand the physical mechanisms of flow boiling crisis, simulated tests have been conducted to observe the hydraulic behavior of the coolant and to measure the thermal response of the heating surface. To do this, the simulation approaches of the entire CHF testing program are considered as follows. 

Because of the damagingly high temperature of the heater surface at DNB in a water flow, most studies of bubble behavior near the boiling crisis have been conducted on a Freon flow, where the surface temperature is much lower than in a water flow. The validity of the simulations of boiling crisis has been established in many studies, such as those of Stevens Kirby (1964), Cumo et al. (1969), Tong et al. (1970), Mayinger (1981), and Celata et al. (1985). 

Two visual studies of Freon boiling crisis were conducted at the University of Pittsburgh (Lippert, 1971) and at Michigan University (Mattson et al., 1973). Both programs succeeded in identifying the DNB under the saw-shaped bubble layer of subcooled Freon flows as shown in Figures 5.8 and 5.9, respectively... 

The bubble behavior near the boiling crisis is three-dimensional. It is hard to show a three-dimensional view in side-view photography, because the camera is focused only on a lamination of the bubbly flow. Any bubbles behind this lamination will be fussy or even invisible on the photograph, but they can be seen by the naked eye and recorded in sketches as shown in Section 5.2.3. For further visual studies, the details inside bubble layers (such as the bubble layer in the vicinity of the CHF) would be required. Therefore, close-up photography normal and parallel to the heated surf ace is highly recommended. 

Figure 5.3 Visual observation of boiling crisis in water pool. (From Gaetner, 1963. Copyright 1963 by General Electric Co., San Jose, CA. Reprinted with permission.)...

Figure 5.6 Boiling crisis in subcooled Freon flow mass flux 1.5 x 106 lbm hr ft2 (2,030 kg/m2 s), pressure 40 psia (0.27 MPa), A7"sc = 30°F (16.7°C) at boiling crisis. (From Tong 1972. Reprinted with permission of U.S. Department of Energy, subject to the disclaimer of liability for inaccuracy and lack of usefulness printed in the cited reference.)...

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