Numerical simulation of heat transfer in a horizontal falling film evaporator of multiple-effect distillation

The model of outer heat transfer is validated for a limited range of Reynolds numbers. It is compared to experimental data and numerical results from literature and it is shown how the application of the model may be extended to a larger range of outside-Reynolds numbers. Regarding the phenomena inside the tube, the calculated results indicate a significant relevance of the pressure drop on the heat transfer for increased pipe lengths. The reducing influence of accumulating condensate on the overall heat transfer is identified as comparably low. Finally, various combinations of pipe diameters and lengths are analyzed and the associated transmitted heat flows are graphically summarized.