Experimental results for water level oscillations in vertical tubes, together with a theoretical solution for the flow in such tubes considering local and distributed energy losses, are presented and compared. The experimental data were obtained in small scale experiments, allowing adequately controlling the oscillations. The governing equation for the oscillations was obtained by applying the conservation laws of mass, momentum and energy for fluids. It is a second order nonlinear differential equation which was reduced to a first order differential Bernoulli equation. The obtained solution is composed by two different equations, one for the upwards motion and the other for the downwards motion, which together reproduce the oscillatory damped behavior of such flows. Numerical solutions of the differential equation were also checked. The experimental data and the theoretical and numerical results showed a good agreement between measured and calculated values of velocity and surface level for the first periods of oscillation.
Abstract. The shape of pipeline structure, fluid medium and flow state have important influence on the heat transfer and mass effect of fluid. In this paper, we investigated the mass transfer behavior of Non-Newtonian fluid CMC solution with 700ppm concentration in five different-sized axisymmetric wave-walled tubes for pulsatile flow. It is revealed that the effect of mass transfer is enhanced with the increase of oscillatory fractions P based on the PIV measurements. Besides, mass transfer rate was measured by the electrochemical method in the larger oscillatory points rate range. It is observed that mass transfer rate increases with the increase in P and reached the maximum mass transfer rate at the most optimal oscillatory fractions Popt. After reaching the optimal oscillatory fractions Popt, the mass transfer rate decreases with increasing P.
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