Flow pattern based correlations of two-phase pressure drop in rectangular microchannels

Highlights: ► Glass microchannels with embedded pressure ports were fabricated to obtain accurate measurements. ► The assessments of seven HFM (Homogeneous Flow Model) and ten SFM (Separated Flow Model) were conducted. ► The results indicate models shows best estimations. ► In addition, the pressure drop is well agreed with flow pattern tendency. ► Based on two-phase flow patterns, new correlations were proposed for both homogeneous and separated flow types. - Abstract: Numerous pressure drop correlations for microchannels have been proposed; most of them can be classified as either a homogeneous flow model (HFM) or a separated flow model (SFM). However, the predictions of these correlations have not been compared directly because they were developed in experiments conducted under a range of conditions, including channel shape, the number of channels, channel material and the working fluid. In this study, single rectangular microchannels with different aspect ratios and hydraulic diameters were fabricated in a photosensitive glass. Adiabatic water-liquid and Nitrogen-gas two-phase flow experiments were conducted using liquid superficial velocities of 0.06–1.0 m/s, gas superficial velocities of 0.06–72 m/s and hydraulic diameters of 141, 143, 304, 322 and 490 μm. A pressure drop in microchannels was directly measured through embedded ports. The flow pattern was visualized using a high-speed camera and a long-distance microscope. A two-phase pressure drop in the microchannel was highly related to the flow pattern. Data were used to assess seven different HFM viscosity models and ten SFM correlations, and new correlations based on flow patterns were proposed for both HFMs and SFMs.