Three existing pressure-drop models are validated and analyzed with experimental data compiled from the research database. From the analysis, it was found that the pressure-drop prediction results from the models are not very accurate and not consistent with all experimental datasets. A new pressure-drop model was consequently created based on the findings from the study, and experimental data from the database were used to validate the model to produce more accurate and consistent predictions. The new pressure-drop model was tested on experimental datasets that were in the database and also with experimental datasets that were not in the database. Good and consistent results were achieved, and the new model proved capable of predicting pressure drops for different pure refrigerants and refrigerant mixtures flowing inside different configurations of microin tubes for both condensation and evaporation.

Three existing condensation heat transfer models are validated using 544 experimental data points for pure refrigerants and refrigerant mixtures. The Cavallini et al. (1999) model predicts well with the pure-refrigerant data sets. However, the Cavallini et al. (1999) model fails to predict the refrigerant-mixture data sets. The Yu and Koyama (1998) model, which is applicable for the pure refrigerants only, fails to predict most of the R22 data sets. The Kedzierski and Goncalves (1999) model, which is applicable for both pure refrigerants and refrigerant mixtures, yields relatively high mean absolute deviations for most of the pure-refrigerant data sets. The Kedzierski and Goncalves (1999) model does not account for the mass transfer thermal resistance in refrigerant mixtures. A new pure-refrigerant model and a new refrigerant-mixture semi-empirical model have been developed. Both the new models successfully predict the experimental data for pure refrigerant and for refrigerant mixtures.