Flow-Regime-Based Model for Pressure Drop Predictions in Microchannels

A flow-regime-based pressure drop model is developed to correlate experimental data in the intermittent and annular flow regime. For the intermittent region, an alternative method for microchannel pressure drop predictions based on the average kinetic energy of the mixture is developed. A parameter based in the Weber number, the Lockhart-Martinelli parameter, and the liquid-to-vapor density ratio is proposed for pressure drop predictions in the annular flow region. The two correlations were built on experimental data of R-410A, R-134a, and air-water mixtures with mass fluxes ranging from 50 to 300 kg/(s·m2), with quality ranging from 0 to 1. Six-port and fourteen-port aluminum microchannel tubes with hydraulic diameters of 1.54 mm and 1.02 mm, respectively, were used for the two-phase pressure drop experiments. Entrance/exit pressure drops were directly measured with an additional experiment. The losses due to the entrance/exit zones have been found to exhibit homogeneous flow characteristics, and were correlated to a homogeneous flow parameter based on the kinetic energy of the flow field.