Case Studies in Thermal Engineering (Mar 2022)
Experimental investigations on indirect contact type liquid desiccant cooling systems for high latent heat load application
Abstract
Heat driven sorption technologies are promising alternatives to traditional vapour compression based systems for comfort cooling. High latent heat load applications and improved indoor air quality are best accommodated by the various sorption technologies available and desiccant-based cooling systems. Liquid desiccant-based systems are preferred over solid desiccant-based systems due to lower pressure drop, the possibility of continuous operation, solar energy for regeneration, and the ease of storage of regenerated desiccant solution. This paper investigates the experimental performance of indirect contact type liquid desiccant cooling systems for applications involving a high latent heat load. An experimental test rig includes a dehumidifier, regenerator, and heat exchanger, all been developed, fabricated and connected to work as one unit. The dehumidifier and regenerator transfer the heat and mass from liquid desiccant to the air membrane making the arrangement an indirect contact type of heat exchanger. Lithium Chloride solution is used as a desiccant solution in experiments, and Polyvinylidene Fluoride is used as a membrane material. The effect on dehumidifier performance parameters like rate of moisture removal, sensible heat effectiveness, and latent heat effectiveness is studied for varying inlet air parameters as well as for various liquid desiccant operating parameters. The inlet air specific humidity ranges from 10 to 13 g/kg da, and the inlet air flow rate varies from 2 to 4.5 kg/hr. The inlet desiccant temperature supplied at 24–32 0C with desiccant concentration varied 30–42%, and the desiccant solution mass flow rate is supplied in the range of 3–11 kg/h. Various dehumidifier performance parameters like rate of moisture removed, latent heat effectiveness and sensible heat effectiveness are discussed. Based on the experimentation, utilizing the optimum values of inlet air parameters or optimum values of desiccant solution parameters has been recommended to achieve the cooling system's highest possible latent heat effectiveness.
