Enhancing industrial vertical falling film evaporation through modification of heat transfer surfaces – an experimental study

Abstract

In this study we introduce and experimentally study modifications of heat transfer surfaces as a means to improve the heat transfer in evaporative vertical falling film units. We look at two modified tubular surfaces and compare the obtained results to those acquired using a similar smooth surface. We carry out experiments with two fluids of significantly different viscosities and work with a broad range of industrially relevant operating conditions, with Kapitza (Ka) and Reynolds (Re) numbers in the range of Ka = 500–10 000 and Re = 100–2 000, respectively. We find that the heat transfer rate in a pilot-scale unit can be improved by 50% to more than 100%, depending on geometrical features (e.g. sharpness) of the modified surface. Our results pave the way for increasing the overall efficiency of industrial evaporation plants by increasing the energy intensity of the evaporator per unit area through carefully tailored modifications of heat transfer surfaces.