The research proposes an alternative air-conditioning system based on desiccant dehumidification and evaporative cooling. The concept uses a channel type heat exchanger, with alternate channels for dehumidification and evaporative cooling. The dry channels are coated with silica gel desiccant. The wet channels are sprayed with water. The primary air to be cooled is passed through the dry channels, wherein it is simultaneously cooled and dehumidified. A part of the dehumidified air of the desiccant channels is branched into the evaporatively cooled channels. This phenomenon, known as dew point evaporative cooling, has the potential to cause a significant reduction in the dry bulb temperature (DBT), which can be brought down to as low as the dew point temperature (DPT) of the dehumidified air. The paper’s novelty lies in the simultaneous usage of a Desiccant Coated Heat Exchanger (DCHE) and dew point evaporative cooler (DPEC) in a single compact model, which has not been studied to date, as sourced by the authors. The main area of interest has been to study the interplay between the simultaneous adsorption and evaporative cooling phenomena, and their effect on each other. Numerical analysis of two different configurations of the cooler (crossflow and counterflow) was undertaken on MATLAB version R2021a.
Results show that the proposed system can bring about 4-5℃ of additional cooling as compared with existing literature on desiccant based evaporative coolers. Data shows that the counterflow configuration performs better in all three modes, and having a higher dehumidification cycle time, and a lower combined regeneration and cooling cycle time as compared to crossflow configuration. It was also observed that the counterflow configuration required a regeneration temperature of only 52.3℃ to operate in a dual mode setup wherein one setup is in dehumidification mode, and the other in regeneration-cooling mode. The crossflow configuration requires a minimum of 78.7℃ to achieve the same result. Another interesting deduction was that if the regeneration temperature of the counterflow configuration is increased to 82.5℃, then its cooling capacity gets doubled, due to further reduction in regeneration cycle time. This allows for using three parallel setups, wherein two setups would be in dehumidification mode at any given point of time, and only one in regeneration-cooling mode. Thus, the study provides a detailed insight into the temperatures and cycle times possible for optimum utilisation of the heat exchanger as a sustainable and green air-conditioning system.