Influence of plate surface temperature on the wetted area and system performance for falling film liquid desiccant regeneration system

The falling film liquid desiccant air conditioning system is a promising technology. The wetted area, as a key factor affecting the system performance, is significantly influenced by the plate surface temperature. With a single channel internally heated regenerator, this paper experimentally investigated the impact of plate temperature on the wetted area and system performance, by obtaining the film area and temperature with a thermal camera. LiCl was chosen as the desiccant. By reducing the film contraction in the transverse direction, the increase of plate surface temperature could enhance the wetted area significantly, especially for the low solution mass flow rate. The growth rate of area increased from 0.0017 to 0.0022 m2/°C when the flow rate reduced from 0.062 to 0.034 kg/s. The regeneration performance also increased with the temperature. A theoretical model with an analytical solution was developed to obtain the wetted area by describing the film contraction caused by the Marangoni effect. A good match was observed for the prediction and experimental results, with an average error of 10.8%. Furthermore, the wetted width was numerically found to also increase with the decrease of film thickness and contact angle, and its change with the solution concentration was slight. This research helps researchers and engineers to accurately predict the wetted area of falling film and to improve the heat and mass transfer performance of liquid desiccant regeneration system.