Prediction of dryout in evaporation of falling films on horizontal plain tubes

Abstract

Accurate prediction of dryout during falling film evaporation is important to ensure good performance as post-dryout heat transfer coefficients are very low. No prediction method verified with a wide range of data is presently available and there has been a need for one. A new correlation is presented for dryout of saturated fluids on plain horizontal tubes. It has been verified with data for seven fluids from eight sources. The fluids are R-11, R-134a, R-236fa, R-410A, isobutane, and propane. Other parameters in the database are: heat flux from 0.2–95 kW m−2, reduced pressures from 0.00164 to 0.15, and liquid Reynolds numbers from 13 to 970. The new correlation predicts the data from single tubes and arrays of tubes with mean absolute deviation (MAD) of 15.8%. The same data were also compared to other correlations and those had much higher deviations. The new correlation and results of comparison with test data are presented and discussed.