Assessment of pilot direct contact membrane distillation regeneration of lithium chloride solution in liquid desiccant air-conditioning systems using computer simulation

Abstract

Membrane distillation (MD) has been increasingly explored for treatment of various hyper saline waters, including lithium chloride (LiCl) solutions used in liquid desiccant airconditioning (LDAC) systems. In this study, the regeneration of liquid desiccant LiCl solution by a pilot direct contact membrane distillation (DCMD) process is assessed using computer simulation. Unlike previous experimental investigations, the simulation allows to incorporate both temperature and concentration polarisation effects in the analysis of heat and mass transfer through the membrane, thus enabling the systematic assessment of the pilot DCMD regeneration of the LiCl solution. The simulation results demonstrate distinctive profiles of water flux, thermal efficiency, and LiCl concentration along the membrane under co-current and counter-current flow modes, and the pilot DCMD process under counter-current flow is superior to that under co-current flow regarding the process thermal efficiency and LiCl concentration enrichment. Moreover, for the pilot DCMD regeneration of LiCl solution under the counter-current flow, the feed inlet temperature, LiCl concentration, and especially the membrane leaf length exert profound impacts on the process performance: the process water flux halves from 12 to 6 L/(m 2 h) while thermal efficiency decreases by 20% from 0.46 to 0.37 when the membrane leaf length increases from 0.5 to 1.5 m.

Direct rapid formation of polyacrylonitrile/lithium chloride antibacterial nanofiber for liquid desiccant air‐conditioning systems with ‘island nozzle’

“…3,4 However, this dehumidifying system not only has high energy consumption, but also molds and bacteria grow on the wet surfaces of the chilled water coils of the air handling units during the condensation of moisture, which can affect the indoor air quality and cause health issues. 5,6 Therefore, the liquid desiccant airconditioning system, which uses liquid as dehumidification agent and utilizes low-grade energy such as solar energy and waste heat to achieve dehumidification function, [7][8][9][10] has received increasing attention and has broad application prospects because it can overcome the above problems and remove gas pollutants (such as volatile organic compounds), biological contaminants (such as bacteria and viruses) and particulate matter (such as dust and smoke). 11 Packaging material is essential as the core component of the dehumidifier in the liquid desiccant air conditioning system, it provides sufficient contact area for the gas-liquid two-phase and makes the solution dehumidification system obtain higher heat and mass transfer coefficient.…”