Condensation flow inside tubes: A review of heat transfer coefficient measurement techniques, experimental databases and prediction methods

Heat transfer coefficient (HTC) is one of the most important parameters for modeling forced flow condensation inside tubes. This manuscript presents an extensive review of HTC measurement techniques, experimental databases, and prediction methods for in-tube flow condensation to evidence the latest literature achievements and identify new research opportunities. HTC measurement techniques were reviewed, classified, and the most used techniques were identified along with their main characteristics. Experimental databases from the literature were grouped for analysis, totaling 15,021 data points for channel diameters ranging from 0.067 to 20.8 mm, 82 working fluids, horizontal and vertical flow directions, and 4 different tube wall materials for smooth tubes. The measurement techniques and uncertainties of individual databases were identified and discussed. Recently identified trends are the increasing interest in low GWP refrigerants, new fluid mixtures, and experiments for small-diameter channels. Many of these experimental conditions were not incorporated or tested on previous correlations, representing an extrapolation when doing so. A total of 34 prediction methods, proposed from 1958 to 2024, were evaluated and compared to this broad database to verify their prediction errors and physical fundamentals. The best predictions obtained a mean absolute percentage error of 23.4 %, showing that further work for minimizing the experimental uncertainties is still needed. In addition, HTC values higher than 10 kW/m(2)K are commonly observed in recent experiments. One of the challenges identified for new measuring techniques is the measurement of such high values of HTC while keeping low uncertainty levels. The experimental database collected in this work is available for download in the supplementary material.