Study of Flow Boiling Characteristics of a Microchannel Using High Speed Visualization

Abstract

This paper presents the visualization results obtained for an experimental study ofR134a during flow boiling in a horizontal microchannel. The microchannel used was a fused silica tube having an internal diameter of 781 um, a heated length of 191 mm, and was coated with a thin, transparent, and electrically conductive layer of indium-tin-oxide (ITO) on the outer surface. The operating parameters during the experiments were: mass flux ¡00^00 kglm^ s, heat flux 5-45 kWI m^, saturation temperatures 25 and 30° C, corresponding to saturation pressures of 6.65 bar and 7.70 bar and reduced pressures of 0.163 and 0.189, respectively. A high speed camera with a close up lens was used to capture the flow patterns that evolved along the channel. Flow pattern maps are presented in terms of the supeiftcial gas and liquid velocity and in terms of the Reynolds number and vapor quality plots. The results are compared with some flow pattern maps for conventional and micro scale channels available in the literature. Rigorous boiling and increased coalescence rates were observed with an increase in the heat flux.

Intermittent Flow Pattern on Two Phase Flow Boiling with Horizontal Microchannel

“…Ali et al 1) was conducted experiment with visualization flow pattern using high speed camera in microchannel. The horizontal test section was a tube with internal diameter of 781 µm and heated length of 191 mm.…”

“…Ali et al 2) was plotting the two phase flow pattern map with concerning superficial velocity of both gas and liquid. The experiments showed the increased velocity of gas results in a transition of flow regimes, viz.…”