Cascaded liquid desiccant system for humidity control in space conditioned by cooled membrane ceiling and displacement ventilation

Abstract

Displacement ventilation combined with liquid desiccant membrane cooled ceiling is an efficient Heating, ventilation and Air conditioning system. However, it has limited performance in office spaces located in hot and humid climates and characterized by high internal loads due to the lack of ability to control the humidity. This study proposes a cascaded liquid desiccant system from the ceiling to be used in a liquid desiccant heat and mass exchanger in the supply duct to control the humidity in the space and reduce energy cost. To achieve this goal, a predictive integrated model for different components of the cascaded liquid desiccant system is developed to predict the comfort level and the air quality inside the space as well as the energy consumption of the system. The model was validated experimentally in a climatic chamber. The validated integrated model was applied to a case study to assess the effectiveness of the system in the hot and humid climate of Beirut. Two configurations of the liquid desiccant membrane cooled ceiling and mass exchanger were simulated and found to provide acceptable humidity for comfort in the occupied zone of the space. However, the cascaded system cooling and heating energy during the cooling season were found lower by 21.25percent and 16.23percent respectively in August when compared to a liquid desiccant membrane cooled ceiling, displacement ventilation and membrane exchanger system with different configuration. The cooling and heating energies were also lower in the cascaded system compared to a liquid desiccant membrane cooled ceiling, displacement ventilation and conventional dehumidification method.