Theoretical Study on Boiling Heat Transfer Characteristics Under Wide-Range Working Conditions Inside Horizontal Micro-Fin Tubes

A database containing flow boiling heat transfer characteristics of various refrigerants inside micro-fin tubes with different structures under wide-range working conditions was built. Then the influencing mechanisms of refrigerant thermo-physical properties, fin structure and working conditions on nucleate boiling and forced-convection heat transfer characteristics were analyzed qualitatively. To reveal the actual heat transfer mechanism of refrigerant inside the micro-fin tube, some existing correlations were selected for evaluating the experimental data within the database. The comparison results indicate that there is no correlation achieving high-precision prediction for all experimental data and the prediction accuracy of correlation is influenced significantly by working conditions, particularly mass flux and heat flux. Finally, to acquire a general theoretical model, a new correlation was proposed based on the fitting mechanism of the Hamilton et al. correlation as it exhibits the most concentrated prediction deviation, which means the number of variables affecting correlation prediction effect is the least. After verification, it can be discovered that the average prediction deviation of the new correlation for all experimental data is less than ±30% when the two-phase fluid Reynolds number is less than 3500, which is enough to validate the application value of the theoretical model.