Design Guidelines and Performance Study on a Structured Packed Liquid Desiccant Air-Conditioning System

Structured packing represents the newest development in high efficiency, high capacity packing for heat and mass transfer in contrast to the traditional, randomly placed packing material. The main objectives of this study are to develop design guidelines and to assess the performance of a structured packed liquid desiccant-evaporative cooling system in the modified comfort zone. Theoretical and experimental studies of the simultaneous heat and mass transfer between air and desiccant in a packed absorption tower are conducted. Tri ethylene glycol (TEG) is used as a desiccant and cellulose rigid media pads are used as structured packing. The packing arrangements have provided minimum carryover of TEG and produced low pressure drop. Through the study of the absorber, important design variables are defined. It is found that high liquid flow rates do not have a significant effect on the system performance if the liquid to airflow ratio exceeds the value of 2. The theoretical model is compared with the experimental results. The effect of dehumidification on evaporative cooling performance is carried out. A reduction of 4.5°C to 9°C in the wet-bulb temperature was obtained from the dehumidifier. Design guidelines have been written to help in designing such systems.

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