Research on the condensation of the ammonia–water mixture on a horizontal smooth tube

This paper reports on the experimental research and the theoretical analysis conducted to study the condensation of the ammonia–water mixture on a horizontal smooth tube. Experiments were carried out with ammonia concentrations and wall subcoolings ranging from 62% to 95% and from 45 °C to 90 °C, respectively. Experimental results of the overall condensation heat transfer coefficients (HTCs) are reported and discussed. A theoretical model based on the analytical method proposed by Colburn and Drew was developed. The model was able to predict the trends of the experimental HTCs for the ranges of concentrations and wall subcoolings considered in the experiments. The heat flow and the overall condensation HTCs were slightly overestimated with mean errors of 9.3% and 11.2%, respectively. The theoretical results revealed that the ammonia mass transfer in the vapour phase has a significant effect on the heat and mass transfer coefficients and, consequently, on the overall condensation HTCs. Finally, a calculation procedure was established to estimate the vapour mass and heat transfer coefficients from experimental data. The results are shown as dimensionless correlations.