A Novel Fluid Flow Demonstration/Unit Operations Experiment

Abstract

Demonstration of laminar and turbulent flow using water in one experimental unit has always been a challenge. One can achieve one of the two defined flow regimes by varying tube diameter; however, the versatility to move across a decade or more in Reynolds number with a single tube diameter is generally difficult. A unit operations fluid flow experiment composed of a two ¾-inch ID glass tubes, 36 inches long, has been developed that allows demonstration of flow in all flow regimes with ease. One of the tubes is empty and contains no flow elements (typical flow inside a pipe); the other tube contains a multi-element, 33-inch long, static mixer. Using a secondary dye injection system, students conduct experiments in which the various flow regimes (laminar, transition, or turbulent) may be observed in the empty tube. The effects of the static mixer blending the dye into the water stream can be observed in the other tube. Students record the flow effects in their experiments using still and motion digital photography. Pressure transducers, located at the entrances and exits of the tubes, allow quantitative measurement of pressure drop across each tube to be observed. Students can then compare their results with pressure loss predictions using information found in the literature such as a Fanning Friction Chart. The experiment has been technically successful and is very popular with our students. This paper presents the evolution of this experiment and on the results that students are able to observe and evaluate. Nomenclature D Inside diameter of pipe or tube, m F Frictional pressure losses in flow systems, m 2 /s 2 f Fanning friction factor, dimensionless f M Moody friction factor, dimensionless L Length of tubing, m L eq Equivalent length of tubing for similar pressure drop, m P System pressure, N/m 2 Re Reynolds number (defined in Equation 1), dimensionless v velocity, m/s V Volumetric flow rate, m 3 /s Subscripts 1 Entrance condition 2 Exit condition ref Reference condition • Session 2313