Energy losses in junctions are often found by using an assumed loss coefficient for the particular geometry. While this coefficient remains nearly constant under turbulent conditions, this is not true for laminar flow. The loss coefficient through a dividing junction tends to decrease as a function of Reynolds number converging to some value once fully turbulent flow occurs. Research has been done to catalog losses for various geometries under turbulent flow; yet, there has not been the same detailed research for the laminar conditions. This is mostly due to many applications at the macro scale where turbulent flow is prevalent. Flow in microchannels and nanochannels is mostly laminar. Applications at this small scale have created a demand for the study of these loss coefficients under the laminar flow conditions.
This paper focuses on simulations done of flow through a square-cornered tee-junction with a rectangular cross sectional area of 6 by 7 millimeters. The fluid consisted of a glycerin and water mixture that was 30 percent water and 70 percent glycerin by volume. Measurements were made of an actual mixture’s density and viscosity and these parameters were used in the simulations. The mixture was chosen to give sufficient pressure drop to measure in validation experiments. Using these simulations, a detailed account of the energy losses in the junction was observed as a function of Reynolds number. The Reynolds number range in this study was 1–100. Higher Reynolds numbers were simulated where signs of a transition to turbulence were observed.
The stagnation loss coefficient, which includes kinetic energy and pressure changes through the junction, was found to be inversely proportional to Reynolds number. Initial experimental verification has been performed, in which the experimental stagnation loss coefficient followed the same trend as the simulations. Additional experimental validation is underway.