The Effects of Inlet Flow Conditions on Gas-Liquid Two-Phase Flow in a Micro Tube

Abstract

In the present study, the effects of inlet geometry on the microscale two-phase flow patterns have been examined. The relationships among the flow pattern, the void fraction, the pressure loss and the heat transfer coefficient have been also investigated under different inlet flow conditions. At the inlet, a stainless steel tube is inserted into the micro glass tube, of which inner diameter is 300 and 600 μm. The gas and liquid paths and the diameter of the inner tube are interchangeable. The flow patterns are recorded at the inlet and also in the developed region in the micro tubes. The flow patterns observed in the 600 μm tube are bubbly, slug, churn and annular flows, while bubbly and churn flows are not present in the 300 μm tube. For bubbly and slug flows, bubble formation process is found to be strongly affected by the inlet conditions. Accordingly, the pressure loss as well as the heat transfer rate are changed. In addition, the bubble size is not uniquely determined; bubbles of different sizes are observed in repeated experiments under the same inlet flow conditions. On the other hand, for churn and annular flows, the flow patterns are not affected by the inlet conditions.

Flow Boiling Pressure Drop of R134a in Microdiameter Tubes: Experimental Results and Assessment of Correlations

“…) in micro tubes approaches unity. Serizawa et al (2002), Hayashi et al (2007) and Saisorn and Wongwises (2008) found that the measured void fraction in micro tubes agrees well with the homogeneous void fraction, i.e. slip ratio ≈ 1.…”

Heat transfer characteristics of gas-liquid two-phase flow in microtubes

“…5.11 (H)). [54], the present pressure loss measurements at low gas flow rate is found to be matching well with the pressure measurements conducted by Hayashi et al [54] where their measurements were performed at a higher gas flow rate using a similar set up. drop.…”

“…Flow Visualization and Heat Transfer Measurements of two-phase Flow in Microtubes the pressure drop for the bubbly and slug flows. Conversely, it will overestimate the pressure drop for the churn and annular flows according to the results reported by Hayashi et al[54]. Furthermore,Fig.…”

“…Hence, the flow patterns observed by them were rather random. However, no periodically flow pattern was observed by Hayashi et al[54] with the channel inlet design shown inFig. 2.11.Kawaji et al[55] designed the inlet geometric shown inFig.…”

“…However, they demonstrated that the ratio of tube length to diameter (L/D) has only minor effect to the overall heat transfer rate.Thulasidas et al[86] investigated the bubble train flow in capillaries of circular and square cross-sectional channels. The enhanced heat transfer rates were concluded to be attributed to the bubble diameter and the thickness of the thin film between the bubble and the channel wall.Gas liquid concurrent flow without phase change experiments were conducted byHayashi et al[54] to examine the effects of inlet flow conditions on glass tube of 300 and 600 µm channels. They found that the bubble formation process was strongly affected by the inlet conditions and pressure loss was affected by the bubble size.…”