VISUAL STUDY OF FLUID DYNAMICS IN WICKLESS TRANSPARENT HEAT PIPES
Though heat pipes are recognized as a viable heat transfer device for many different applications, the thermal mechanisms driving the heat transfer are still not fully understood. By fabricating and testing a transparent sapphire heat pipe, with water as the working fluid, the dominant mechanisms of boiling and condensation were visualized. The results of this investigation suggest that for low operating pressures there is a complex geyser boiling regime occurring in the evaporator section, at lower powers (~20 W) slugs of water were observed, and explosive boiling was noted at higher powers (~70 W). These phenomena were observed using high speed imagery and comparisons made with the corresponding local temperature.