CLOSE AND OPEN CYCLE ADSORPTION KINETICS: DEVELOPMENT OF CORRELATION FOR DESICCANT AIR-CONDITIONING
CLOSE AND OPEN CYCLE ADSORPTION KINETICS: DEVELOPMENT OF CORRELATION FOR DESICCANT AIR-CONDITIONING
Muhammad Sultan1,4, Muhammad H. Mahmood2,4, Takahiko Miyazaki3,4, Shigeru Koyama3,4, Zahid M. Khan1
ABSTRACT
Adsorption kinetics by desiccant-water pairs always play curial role in the development of low-cost thermally driven desiccant air-conditioning systems. It also influences various operating parameters of desiccant air-conditioning systems e.g. switching/cycle time, desiccant/system size, and regeneration temperature etc. Usually it is difficult to measure open-cycle adsorption kinetics precisely in adsorption heat pump systems. Therefore, present study provides an experimental comparison of close and open cycle based water vapor adsorption kinetics for the development of desiccant air-conditioning system. In this regard, a polymer based hydrophilic sorbent was used for close and open cycle adsorption measurements. Gravimetric method based magnetic suspension adsorption measurement unit was used for close-cycle adsorption kinetics measurements. However, the open-cycle adsorption kinetics was determined from the instantaneous measurement of air relative humidity and dry-bulb temperature in and out to the desiccant block while assuming the equilibrium between air and desiccant sides. Both experimental results were analyzed using linear driving force (LDF) model which presents the best regression of the experimental data. Furthermore, an empirical correlation of close to open cycle water vapor adsorption kinetics was established. Results revealed that the open-cycle kinetics of water vapor adsorption was 0.65 times slower (on average) than the close-cycle, which was more likely due to the complex mechanism of adsorption kinetics in open system. This study can be useful to determine the open-cycle adsorption kinetics from the close system data for designing the desiccant air-conditioning system.
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