A combined IR imaging and hygrometric approach for preliminary mass transfer evaluation in indirect evaporative cooling systems

The rise in average temperatures due to the greenhouse effect, along with the gradual improvement in people's life quality and the resulting increase in desired comfort levels, is driving a continuous surge in cooling demand, both for industrial and residential applications. The growing use of conventional vapor compression cooling systems is leading to a rapid rise in energy consumption, highlighting the need for more energy-efficient alternatives. In this context, evaporative cooling systems are regaining interest thanks to innovative designs that outperform older architectures. The effectiveness of such systems is often linked to the evaporation capacity of the heat transfer surface. This study experimentally assesses the mass transfer behavior of a metal surface coated with a cotton layer under evaporative heat transfer regime. For this purpose, an experimental setup was built to simulate a flat channel where air at different inlet temperatures is circulated, while a current generator heats the wetted heat transfer surface via the Joule effect, simulating the behavior of an indirect evaporative cooling process. A first infrared camera and thermo-hygrometers are used to monitor the air temperature and humidity along the channel, while a second infrared camera provides the thermal mapping of the wet surface. The combination of these two approaches allowed for the identification of air temperature profiles in the channel and provided preliminary insights into the spatial distribution of the mass transfer coefficient.