Simplified analysis of coupled heat and mass transfer processes in an open cycle solar C/R

Application of the open cycle solar collectors/regenerators (C/R) is an effective way to utilize low-grade solar thermal energy to concentrate desiccant solution for air-conditioning. This paper aims at developing an analytical model for the coupled heat and mass transfer process inside an open cycle solar C/R. Within narrow range of operating conditions, linear approximations were made to find the dependence of equilibrium humidity ratio on the solution temperature, constant properties and coefficients. New parameters, which represent the heat and mass transfer driving forces, were defined and the basic differential equations were rearranged to obtain two coupled non-homogeneous linear equations. The effects of the climate conditions were organized as non-homogenous parts, which allow direct evaluation. The analytical expressions for water evaporative rate and outlet conditions of the desiccant solution and scavenge air were further developed based on the analytical solution. A parametric analysis of the solar OR has been performed to reveal the effects of climate conditions and system variables on the rate of evaporation of water from the solution. The ratio of the solution to the air mass flow rate was also found to be an important controlling parameter. Based on the simulation results, the possible optimization methods for the solar C/R and operating variables were also discussed.