Prediction of frictional pressure drop during flow boiling of refrigerants in horizontal tubes: Comparison to an experimental database

An experimental frictional pressure drop database for smooth tubes including 485 points from the literature is compared to four well-known correlations and also to the phenomenological model by Moreno Quibén and Thome. This model is new and has never been compared to those experimental data. The Grönnerud correlation and the flow pattern based two-phase frictional pressure drop model by Moreno Quibén and Thome display the best prediction. Seventy-four percent of the data are predicted by the latter model within a ±30% error band. Furthermore, the model by Moreno Quibén and Thome predicts a maximum pressure drop before the annular-to-dryout transition, i.e. as usually in the annular flow regime. An explicit expression (never proposed before) for the vapor quality corresponding to the maximum pressure drop (xM) is developed here. Based on this maximum and on the pressure drop for liquid and vapor, a simple linear function is developed for predicting the frictional pressure drop. This method presents the best accuracy and predicts almost 86% of the data within a ±30% error band. This method does not include any new empirical parameters and can be used for a wide range of experimental conditions. Furthermore, the experimental data were also segregated into flow regimes and compared to each individual prediction method. The linear approach presents the best statistics for each flow regime. In addition, an experimental frictional pressure drop database for helically microfinned tubes including 673 points from the literature is also compared to three existing correlations. The Kuo and Wang correlation presents the best statistics, predicting almost 85% of the data within a ±30% error band.