Flow of Single-Phase Water and Two-Phase Air-Water Mixtures through Sudden Contractions in Mini Channels

Pressure drop through sudden contraction in small circular pipes have been numerically investigated, using air and water as the working fluids at room temperature and near atmospheric pressure. Two-phase computational fluid dynamics (CFD) calculations, using Eulerian– Eulerian model with the air phase being compressible, are employed to calculate the pressure drop across sudden contraction. The pressure drop is determined by extrapolating the computed pressure profiles upstream and downstream of the contraction. The larger and smaller tube diameters are 1.6 mm and 0.84 mm, respectively. Computations have been performed with single-phase water and air, and two-phase mixtures in a range of Reynolds number (considering all-liquid flow) from 1000 to 12000 and flow quality from 3 2 1.9 10 to 1.6 10     . The contraction loss coefficients are found to be different for single-phase flow of air and water. The numerical results are validated against experimental data from the literature and are found to be in good agreement. Based on the numerical results as well as experimental data, a correlation is developed for two-phase flow pressure drop caused by the flow area contraction.