Abstract
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.
Highlights
Two-phase flows across singularities such as bend, contraction and expansion are commonly seen in piping of many industrial systems and/or devices
The objective of the present study is to clarify the effects of non-Newtonian viscoelastic liquid on the characteristics of flow through sudden expansion for both single-phase and two-phase flows
Main findings are as follows: 1) The two-phase flow patterns were classified into bubble flow, slug flow and annular flow, irrespective of the difference of the test liquid
Summary
Two-phase flows across singularities such as bend, contraction and expansion are commonly seen in piping of many industrial systems and/or devices. Sadatomi et al [2] investigated flow regime, pressure drop, bubble velocity and void fraction for air-water two phase flow through U-bend, sudden expansion and sudden contraction in rectangular minichannel. Kawahara et al [3] conducted experimental investigations on gas-liquid two-phase flows in two kinds of rectangular microchannels with the width of in the larger channels upstream from the contraction were 0.53 or 0.78 mm at 0.230 mm in height, while that in the smaller ones was 0.270 mm at 0.230 mm in height. The contraction test section was from small rectangular channels of 3 × 6 mm and 3 × 9 mm to a small circular tube of 3 mm i.d. Padilla et al [6] conducted experimental studies on two-phase flow of HFO-1234yf, R-134 and R-410A in a 10 mm glass tube with a cross-section area ratio of 0.49. The experimental pressure drop data were used to test six prediction methods from literatures
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