Interfacial heat and mass transfer analysis in solar-powered, packed-bed adiabatic liquid desiccant regeneration for air conditioning

Abstract

In this article, a hybrid photovoltaic–thermal (PV/T) module 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 component is used for desiccant’s regeneration. This combination enhances energy efficiency of the air conditioning system. A simplified analytical model of the complex occurrence of coupled heat and mass transmission phenomenon in liquid desiccant regeneration system powered by a hybrid PV/T module is developed. The interfacial air–desiccant interaction in a structured packing vertical column using lithium bromide solution and Mellapak was analysed. The resulting differential 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 temperatures of air and desiccant solution, moisture content and mass flow rate. It was established 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 the regeneration process. The regeneration rate and effectiveness improved with upsurge in mass flow rate but reduces with a rise in humidity ratio. The optimum flow mix for effective regeneration was therefore established to be 0.847 and 0.00331 kg/min for air and desiccant solution, respectively, for maximum effectiveness of 69.3%. The liquid desiccant solution concentration increased by 30% during when solar radiation peak hours. The obtained theoretical outcomes matched with experimental results from the available literature show a permissible discrepancy of within ±20%, largely due to the fact that the simulation parameters were not the same as the prevailing experimental conditions.