BX-9 Falling Film Evaporation on Horizontal Tubes and Tube Bundles

J. R. Thome

This report reviews falling film evaporation on horizontal single tubes and horizontal tube bundles. Recent research on plain and enhanced tubes is emphasized, as are the effects of small concentrations of viscous fluids (lubricating oils) on performance. As this study shows, enhanced tubes consistently demonstrate very significant heat transfer augmentation for falling film evaporation on horizontal bundles when compared with the performance of plain tubes. This improvement results in much more compact shell-and-tube heat exchanger designs.

The state of the art of heat transfer design methods for horizontal units is also reviewed, and predictive methods for determining the film flow mode between vertical tube rows (droplet, column, and sheet) are discussed. The relative benefits of horizontal falling film units are compared with those of vertical intube units and flooded evaporators. The report concludes with recommendations for future research.