Showing papers by "Thomas F. Irvine published in 1990"

Use of the falling ball viscometer to obtain flow curves for inelastic, non-newtonian fluids

Abstract: This paper reports on a numerical study of the drag force on a sphere moving at constant velocity in inelastic non-Newtonian fluids. The intended application of this work is in the use of the falling ball viscometer to determine flow curves for these fluids. Numerical solutions were obtained for the case of the sphere moving along the axis of a cylinder and ratios of cylinder to sphere diameter from 10 to 40 were examined. In obtaining the solutions inertia was neglected. To represent the fluid's flow curve the modified power law model was used. This model produces Newtonian behavior as the shear rate approaches zero and power law behavior as the shear rate becomes large. A control volume finite difference method was used to calculate the flow field and drag force. Solutions were obtained for values of the power law index from 1.0 to 0.35. Results are compared with others' calculated results in the power law limit and with published experimental data in the transition region of the flow curve. Two methods of using the falling ball viscometer to determine the flow curves of non-Newtonian fluids are presented. The first assumes that sphere drag data cover the Newtonian and power law limits. The second uses an apparent flow index, and an average shear rate and the corresponding shear stress. This is an extension of an approach used by others.

Steady shear viscosity measurements of viscoelastic fluids with the falling needle viscometer

Abstract: Previous measurements by other investigators of the purely viscous properties of viscoelastic fluids using the falling ball viscometer have been shown to yield anomalous results. These occur because the ball falling through the viscoelastic fluid creates a stress field which requires up to one hour to relax to its stress free state before another ball can be dropped. This is experimentally inconvenient. To further investigate this effect for a variety of viscometers, time interval measurements were made on a viscoelastic fluid (AP-273 Separan) using falling ball, falling needle and rotating cylinder viscometers. Although the falling ball measurements showed considerable time interval effects, the falling needle and rotating cylinder measurements did not. Thus the falling needle and rotating cylinder viscometers can be used to conveniently measure the steady shear viscosity of viscoelastic fluids.

Heat transfer from a horizontal bubbling surface to an overlying water pool

Abstract: An experimenl was performed to study the effects of bubbling from a circular, horizontal, fiat plate on the heat transfer to an overlying water pool. The plate had drilled orifices through which nitrogen was injected into an overlying pool of water at atmospheric pressure. For “deep” pools, the heat transfer coefficient was found to increase only about 20% over a range of superficial gas velocities from 0.6 to 8.5cm/s, A turbulent heat transfer model developed by Konsetov was found to agree well with the data from this experiment. This model and the experimental data suggest that under certain conditions the heat transfer coefficient is similar for both horizontal and vertical surfaces. These conditions are, that the bubbles only contribute to the stirring action in the pool and only when the bubbling pool is considered “deep”. When the pool height fell below 60% of its diameter, the heat transfer coefficient decreased almost linearly with pool height. This suggests that there occurs a reduction ...

Heat transfer reviews

Abstract: This book presents tools for continuous improvements in the efficiency of engineering devices, including the recent awareness of the necessity to conserve energy and to find new energy sources. It reports on recent developments in specialized research areas.