Steady-state performance evaluation and energy assessment of a complete membrane-based liquid desiccant dehumidification system

A complete membrane-based liquid desiccant dehumidification system is investigated under the steady operating condition, which mainly consists of a dehumidifier, a regenerator, three heat exchangers, a cold and a hot water supply units. A finite difference mathematical model is developed for the complete system to investigate the system dehumidification performance and energy requirement, and validated by experimental data. The dehumidification performance is evaluated by the system sensible and latent effectiveness and moisture flux rate, while its energy performance is assessed by the total cooling capacity and coefficient of performance. It is found that the number of heat transfer units in the dehumidifier side and solution to air mass flow rate ratio have the most considerable impact on the system performance, while the number of heat transfer units in the regenerator side and solution inlet concentration in the dehumidifier have comparatively weak influences. The system sensible and latent effectiveness can be improved by increasing the dehumidifier side number of heat transfer units before reaching its critical value of 6. However, the amount of moisture being absorbed, total cooling capacity and coefficient of performance decrease with the dehumidifier side number of heat transfer units at the low air flow rate. The critical value of solution to air mass flow rate ratio varies with number of heat transfer units, and it is preferable to keep the flow rate ratio at or below its critical value as further increasing solution flow rate would reduce the system coefficient of performance.