Interfacial Heat and Mass Transfer Analysis in Solar Powered, Packed-bed Adiabatic Liquid Desiccant Regeneration for Air Conditioning

In this article, a hybrid Photovoltaic and Thermal (PV/T) collector generating both electrical and thermal energy simultaneously, has been used in a closed cycle system to provide regeneration heat via a dynamic solar radiation model as well as electrical power relative to location, time of the day and day of the month. Electrical power generated drives the air fan, water and solution pumps while the thermal energy is used in the desiccant's regeneration process for enhanced energy efficient air conditioning system. A simplified analytical model of the complex occurrence of coupled heat and mass transfer process in liquid desiccant regeneration system (LDRS) powered by a hybrid PV/T module is developed. The interfacial interaction between air and liquid desiccant in a structured packed vertical column using Lithium Bromide (LiBr) solution as desiccant and Mellapak structured packing was analysed. The resulting deferential equations are solved simultaneously using separative evaluation and step by step iterative procedure. The system's performance was projected with regeneration effectiveness, subject to varying air and desiccant temperatures, humidity ratio, and mass flow rate. The results showed that, subject to the prevailing local weather conditions, the PV/T module significantly raised desiccant temperature to a high of 67.22 °C good enough for regeneration process. The regeneration rate and effectiveness increased with increase in mass flow rate but reduces with increase in humidity ratio. The optimum flow mix for effective regeneration was therefore established to be 0.847 kg/min and 0.00331 kg/min for air and desiccant solution respectively for maximum effectiveness of 69.3%. The liquid desiccant sollutionconcentration increased by 30% during when solar radiation peak hours. A comparison between the theoretical results and experimental results from available literature shows a permissible discrepancy of within ±20%, largely due to the fact that the simulation parameters were not the same as the prevailing experimental conditions.