Che-Hao Yang

Date of Award

January 2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical Engineering

First Advisor

Clement Tang

Abstract

Gas-liquid phase flow pressure drops occurred in circular channels with sudden contraction or expansion have been studied and investigated experimentally. Especially, water and nitrogen gas phases as experimental fluids were applied in this study. In this study, single phase, deionized water, and two phase, deionized water and nitrogen gas mixture, were under investigation and observation. The diameters of the test channels were 0.5, 0.375, 0.315, 0.19 and 0.14 inches. The setup of the contraction channels, 0.5 to 0.375 inches, 0.5 to 0.315 inches, 0.5 to 0.19 inches, and 0.5 to 0.14 inches were applied. For studying the expansion channels, the reverse of the contraction channels setup were used.

In single phase flow experiment, the ranges of the water mass flows were operated from approximately 5 to 30 g/s. The range of the Reynolds numbers in the smallest contraction channel, area ratio of 0.0784, was from 2016 to 10740. The pressure differences were obtained between 0.59 to 8.46 kPa. The loss coefficients were found to be approximately 0.85 when Reynolds number is above 8000. For the largest contraction channel, area ratio of 0.5652, the range of the Reynolds number became narrower, from 675 to 4014. The range of the pressure drop was to between 0.26 and 0.31 kPa. The loss coefficient remained constant value, which was 0.4, all measured flow rates. The range of Reynolds number in the smallest expansion channel, area ratio of 0.0784, was from 1958 to 10714. The pressure drops data was between 0.64 and 6.69 kPa. The value of the loss coefficient was a constant value of 0.849. In the largest expansion channels, area ratio of 0.5652, the Reynolds number ranges between 780 and 3997. The pressure drops were between 0.18 to 0.295 kPa.

In two phase flow, the water flow rates were controlled between approximately 5 to 30 g/s. The nitrogen gas was added into the experimental test section. The flow rates of the nitrogen were from 0.00049 to 0.029 g/s. The experimental liquid Reynold numbers were recorded from 1310 to 7913 in the smallest contraction channel at the lowest gas mass flow rate. The pressure drops were measured between 0.64 and 3.78 kPa. The liquid Reynolds number range in the largest contraction channel, at the largest gas mass flow rate, was between 1326 and 4031. The range of the pressure drop was 0.19 to 0.46 kPa. For the smallest expansion channel, the range of liquid Reynolds number was from 1290 to 7899 at the smallest gas flow rate. The pressure drop results were between 0.51 and 1.2 kPa. In the largest expansion channel at the largest gas mass flow rate, the pressure drop was between 0.027 and 0.42. The liquid Reynolds number range was between 1323 and 4005. When comparing the experimental data with theoretical and semi-empirical equations, the conditions of incompressible flow, flat velocity profile, vena contracta, slip ratio, homogeneous two-phase flow, and void fraction effect were considered. In our experimental result, the two-phase flow pressure drop data agrees well with the correlations available in the literature. In addition, the two-phase flow pressure drops are observed to be very sensitive to the void fraction. In order to accurately predict the pressure drops with correlations, the void fractions have to be properly determined.

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