Development of a concurrent liquid-liquid core-annular flow column to prevent wall deposition in coagulation studies

This paper describes a method of avoiding the formation of deposits at the wall of a vertical cylindrical tube carrying a steady flow of coagulable fluid (rennetised milk) by providing a cocurrent annular film of inert, immiscible fluid adjacent to the tube wall. A liquid-liquid core-annular flow column, 24 cm long and 3.2 cm diameter, intended for use as a cardiac valve test chamber, was designed and tested to determine the flow conditions under which a continuous annular film of fluid down the wall could be maintained in the presence of a downward flow of relatively low-viscosity aqueous core fluid. Ultimately, for film fluid Reynolds numbers of 880 and above, it was found that a continuously film can be maintained throughout this vertical cylindrical test chamber for all core fluid flow rates attainable in our apparatus. The results indicate that a downward coaxial-flow chamber for milk experiments is indeed feasible. Such coaxial flow systems have been used in reducing pressure drops in the pumping of viscous fluids. Our results suggest also that a core-annular flow might be used to provide protection of pipe walls of short length from fouling or corrosion by a core fluid.