In the present paper, in order to clarity the effects of non-Newtonian liquid properties on the flow, similar experiments have been conducted for that of 0.4 wt% polyacrylamide (PAM) aqueous solutions as the working l...In the present paper, in order to clarity the effects of non-Newtonian liquid properties on the flow, similar experiments have been conducted for that of 0.4 wt% polyacrylamide (PAM) aqueous solutions as the working liquid, and air as the working gas. Liquid single-phase and air-liquid two-phase flow experiments were conducted at room temperature using the horizontal rectangular mini-channel with a sudden expansion. The cross-sectional dimensions of the narrow channel upstream from the sudden expansion were 2.79 mm, 3.09 mm and 2.94 mm in the height (H), the width (W) and the hydraulic diameter (DH), while those for the wide channel were 2.95 mm, 5.98 mm and 3.95 mm. The pressure distributions in the channels upstream and downstream from the expansion were measured with calibrated pressure transducer to determine the pressure change due to the expansion. The flow pattern, the bubble velocity, the bubble length, and the void fraction were measured with a high-speed video camera. The flow pattern map is drawn from the observed flow pattern, i.e., bubble flow, slug flow and annular flow in both the wide and the narrow channels. The bubble length data were compared with the calculation by the scaling law proposed by Kanezaki et al. and Kawahara et al. The pressure change data at the expansion were compared with our previous data together with several correlations in literature. Results of such experiment and comparisons are reported in the present paper.展开更多
In this paper, an extensive numerical study on pressure characteristics in the configuration of sudden expansion with central restriction and suction has been carried out. During study, Reynolds numbers (Re) are consi...In this paper, an extensive numerical study on pressure characteristics in the configuration of sudden expansion with central restriction and suction has been carried out. During study, Reynolds numbers (Re) are considered from 50 to 200, suction (S) from 2% to 10% of inlet mass flow, percentage of central restriction (CR) from 0% to 40% and aspect ratio (AR) from 2 to 6. The effects of each variable on average static pressure distribution and average stagnation pressure distribution have been studied in detail. The results have been compared with the configuration of plain sudden expansion, and sudden expansion with central restriction only. From the study, it is noted that maximum magnitude of average static pressure rise from throat increases with the increase in percentage of suction, flow Reynolds number and percentage of central restriction. This magnitude is higher at lower aspect ratio. Also, it is observed that maximum magnitude of average static pressure rise from throat is always more in case of suction configuration compared to the case of configuration of without suction. Average stagnation pressure drop at any section increases with the increase in percentage of suction and percentage of central restriction, but it decreases with the increase in Reynolds number. It is noted that higher pressure drop at any section occurs at higher aspect ratio. This pressure drop at a section is more in case of suction configuration compared to the case of without suction.展开更多
文摘In the present paper, in order to clarity the effects of non-Newtonian liquid properties on the flow, similar experiments have been conducted for that of 0.4 wt% polyacrylamide (PAM) aqueous solutions as the working liquid, and air as the working gas. Liquid single-phase and air-liquid two-phase flow experiments were conducted at room temperature using the horizontal rectangular mini-channel with a sudden expansion. The cross-sectional dimensions of the narrow channel upstream from the sudden expansion were 2.79 mm, 3.09 mm and 2.94 mm in the height (H), the width (W) and the hydraulic diameter (DH), while those for the wide channel were 2.95 mm, 5.98 mm and 3.95 mm. The pressure distributions in the channels upstream and downstream from the expansion were measured with calibrated pressure transducer to determine the pressure change due to the expansion. The flow pattern, the bubble velocity, the bubble length, and the void fraction were measured with a high-speed video camera. The flow pattern map is drawn from the observed flow pattern, i.e., bubble flow, slug flow and annular flow in both the wide and the narrow channels. The bubble length data were compared with the calculation by the scaling law proposed by Kanezaki et al. and Kawahara et al. The pressure change data at the expansion were compared with our previous data together with several correlations in literature. Results of such experiment and comparisons are reported in the present paper.
文摘In this paper, an extensive numerical study on pressure characteristics in the configuration of sudden expansion with central restriction and suction has been carried out. During study, Reynolds numbers (Re) are considered from 50 to 200, suction (S) from 2% to 10% of inlet mass flow, percentage of central restriction (CR) from 0% to 40% and aspect ratio (AR) from 2 to 6. The effects of each variable on average static pressure distribution and average stagnation pressure distribution have been studied in detail. The results have been compared with the configuration of plain sudden expansion, and sudden expansion with central restriction only. From the study, it is noted that maximum magnitude of average static pressure rise from throat increases with the increase in percentage of suction, flow Reynolds number and percentage of central restriction. This magnitude is higher at lower aspect ratio. Also, it is observed that maximum magnitude of average static pressure rise from throat is always more in case of suction configuration compared to the case of configuration of without suction. Average stagnation pressure drop at any section increases with the increase in percentage of suction and percentage of central restriction, but it decreases with the increase in Reynolds number. It is noted that higher pressure drop at any section occurs at higher aspect ratio. This pressure drop at a section is more in case of suction configuration compared to the case of without suction.
