Effect of Shear Produced by Pipe Fittings on the Drop Size Distributions in Turbulent Flow of Kerosene/Water Mixtures

Author:

Amer EL-Hamouz 

This research paper investigates the effect of shear forces produced by various pipe fittings on the drop size distributions of turbulent kerosene-water mixtures. By utilizing a static mixer and a laser diffraction analyzer, the study demonstrates that the Sauter mean diameter decreases with increased energy dissipation and fluid velocity until a dynamic equilibrium is reached. The findings provide empirical correlations between drop size, Weber number, and energy dissipation rates, offering practical data for the design of industrial oil-water separators.

Key Learnings

• Impact of Pipe Fittings: Shear forces generated by different pipe geometries—such as U-shaped, offset, and horizontal fittings—significantly influence the drop size distribution of kerosene/water mixtures in turbulent flow.
• Equilibrium Drop Size: The Sauter mean diameter (d₃₂) decreases as the number of static mixer elements or fluid velocity increases, eventually reaching a dynamic equilibrium where the rates of drop breakup and coalescence are balanced.
• Energy Dissipation and Weber Number: Experimental data confirms that drop size is inversely correlated with the energy dissipation rate (ε) and the Weber number (W e), with exponents slightly higher than those predicted by Kolmogoroff’s theory due to non-isotropic turbulence.
• Static Mixer Efficiency: Increasing the number of internal mixer elements from 4 to 18 effectively preconditioned the dispersion, producing mean drop sizes ranging from 50 to 700 μm depending on the flow rate.
• Velocity as a Variable: Higher fluid velocities result in higher pressure drops and faster energy dissipation, which leads to finer equilibrium dispersions and shorter residence times required to reach a stable drop size.
• Separation Design: Understanding these dispersion properties and the resulting correlations is essential for the accurate design and optimization of industrial oil-water separators.