On the application of adsorber plate heat exchangers in thermally driven chillers; An experimental and analytical study

The effect of both heat and mass transfer characteristic lengths (HTCL, MTCL) of two different adsorber plate heat exchangers (APHE), for application in an adsorption chiller, on the adsorption and desorption kinetics is investigated. Three representative test frames (TF1-TF3) are prepared to examine small-scale adsorbent samples of the microporous silica gel (Siogel of Oker-Chemie, Germany) applying the volumetric large-temperature-jump methodology at different operating conditions. Based on the obtained kinetic data, an analytical model has been developed to predict the specific cooling power (SCP) and the coefficient of performance (COP) of a single-bed adsorption chiller comprising the studied APHEs. It turned out that, within the tested range of HTCL and MTCL, it can be concluded that, the adsorption kinetics are mainly influenced by the MTCL, while the desorption kinetics are dominated by the HTCL of the adsorbent domain. Applying Siogel as loose pellets inside a newly introduced APHE results in SCPs of 423.3 and 182.7 W center dot kg(-1), at the evaporator temperatures of 15 degrees C and 5 degrees C, respectively. Herein, the condenser and adsorber-end temperatures amount to 30 degrees C and the desorption-end temperature to 90 degrees C. The corresponding COPs amount to 0.50 and 0.40, respectively, which represent quite promising results for further design optimizations.

Automated summary

This study investigates the influence of heat and mass transfer characteristic lengths on the adsorption and desorption kinetics of two different adsorber plate heat exchangers for use in an adsorption chiller. Experimental tests were conducted using microporous silica gel and an analytical model was developed to predict the performance of a single-bed adsorption chiller. The results show that the adsorption kinetics are affected by the mass transfer characteristic length while the desorption kinetics are influenced by the heat transfer characteristic length. Moreover, the use of Siogel as loose pellets in the adsorber plate heat exchanger shows promising results in terms of specific cooling power and coefficient of performance.