Experimental study of falling film evaporation on horizontal tube bundle for a desalination unit

The objective of the present research is to experimentally study the effect of the tube configuration and also the effect of the operating conditions on the evaporation rate of the horizontal tube bundle. An experimental test loop was installed and the water spray on a horizontal tube bundle with three nozzles of fan-jet flat nozzle type. The results show that evaporation rate and Nusselt number are increased by increasing the tube surface temperature, increasing the tube's outer diameter, decreasing the evaporation pressure and decreasing the inlet liquid sub-cooling. The falling distance has little influence on the evaporation rate. Constructing water collector around the bottom-heated tubes enhances the evaporation rate. Also, increasing the gap between the water collector and the outer tube surface, from 0.0 to 4.0 mm, results in increasing the evaporation rate. An empirical correlation has been deduced describing the relation between the average heat transfer coefficient and the affecting operating parameters.