THEORETICAL AND PHYSICAL INTERPRETATION OF ENTRAINMENT PHENOMENON IN CAPILLARY-DRIVEN HEAT PIPES USING HYDRODYNAMIC INSTABILITY THEORIES

The entrainment phenomenon in two-phase parallel flow has been studied from the standpoint of wave instability theories, which are related t o the exponential growth of unstable waves caused by viscous interacti on between the two parallel flowing fluids. Instability theories relat ed to the Kelvin-Helmholtz and the Orr-Sommerfeld problems were review ed and applied to predict the critical air/vapor velocity at the onset of entrainment from a capillary structure. To compare the theoretical criteria with the experimental results, entrainment observed in both air-water and steam-water situations were characterized and classified into three major categories. As results of these comparisons, a modif ied theoretical criterion based on the results of Miles was developed and used to investigate the effect of liquid depth on the critical air /vapor velocity or corresponding Weber number for the given temperatur es, and general trends of the various criteria were examined as a func tion of vapor temperature.