Effect of inlet gas and liquid velocity profiles on drift-flux model in a vertical large rectangular channel

Adiabatic, boiling, and condensing two-phase flows occur in many heat and mass transfer devices. The drift-flux model is essential for predicting the gas or vapor fraction using one-dimensional codes based on the two-fluid model. The drift-flux model specifies the area-averaged relative velocity between two phases in the onedimensional momentum equation of the two-fluid model. In this study, the influence of the inlet gas and liquid velocity profiles on the drift-flux model and the void fraction in a vertical large rectangular channel was investigated. The results showed that the extreme case of non-uniform inlet boundary (NUIB) conditions reduced the drift velocity by a maximum of 16.3 %. Both the channel center peak flow of gas (CPG) and single side wall peak flow of gas (SPG) conditions significantly increased the distribution parameter by more than 20 %. In addition, the CPG and SPG conditions significantly reduced the void fraction by more than 20 %. Finally, the void fraction was predicted for the test data with the six NUIB conditions using the extended drift-flux correlation. The correlation was able to predict the void fractions with an error of approximately +/- 20 % for all NUIB conditions except the CPG condition, which had a maximum error of 54 %.