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A 2-D transient heat and mass transfer analysis is carried out on a longitudinal finned reactor suitable for adsorption-based green refrigeration/heat pump systems employing CO2-activated carbon pair. The study is carried out for a 1 kg adsorbent at constant charging/discharging pressure of 40 bar and 65 bar, respectively, for a fixed charging/discharging time of 300 s. Effects of various geometric parameters viz… reactor aspect ratio (AR), fin height and length, and number of fins (Nf) are studied to achieve an optimum reactor configuration based on maximum CO2 uptake. The results indicate that the addition of fins is crucial for enhancing the CO2 uptake for lower ARs. It is observed that the AR = 7.8; with 32 fins resulted in a maximum CO2 uptake of 1.25 kg/kg of adsorbent. The increment of 9–40% CO2 uptake is observed for all reactor configurations with Nf = 32. The gravimetric analysis revealed the existence of optimum reactor configurations for maximum CO2 uptakes. Based on the optimized conditions, equivalent annular finned models are analyzed for the same mass of the adsorption vessel. The results indicated that similar CO2 uptake could be obtained with lesser annular fins for lower ARs. Moreover, the current study is extended to analyze the desorption performance of optimized reactor configurations under high-pressure conditions. The results confirmed the best desorption performance for the reactor with AR = 7.8 for all external heating fluid temperatures. An increment of 495 and 637% is obtained for AR = 7.8 with Nf = 0 and 32, respectively w.r.t. AR = 0.35 with Nf = 0 at 400 K. [ABSTRACT FROM AUTHOR]

The present investigation explores the effects of the reactor geometry (i.e., the aspect ratio of cylindrical and annular reactors with and without fins, fin spacing, the aspect ratio of fins for finned reactors, and outer to inner diameter ratio for annular unfinned reactors) on the heat and mass transfer characteristics of the adsorbed natural gas storage system employing passive cooling techniques. The authors try to capture how the geometric modification changes the surrounding buoyancy-driven flow physics and improves the proposed novel reactor's storage performance. The study also considers surface radiation, which significantly improves the heat transfer rate, especially for the reactor with lower internal thermal resistance. An attempt is made to reduce the internal thermal resistance of the adsorbent bed by adding 10% graphite by mass and suitably modeling the bed's thermal conductivity and thermal capacity. The result shows that, in terms of adsorbed amount and heat transfer rate, the reactors with an aspect ratio (AR) of 7.8 outperform the other aspect ratios. The simultaneous effects of reactor aspect ratio and fins spacing on the heat transfer and adsorption rates are expounded, and the optimum fin spacing as a function of reactor aspect ratio and diameter ratio (i.e., fin diameter to reactor diameter) is obtained. The best annular reactor outperforms the cylindrical reactor with and without fin in terms of volumetric and gravimetric storage capacity. The annular finned reactor achieves a maximum 33% improvement in storage capacity compared to the adiabatic case and isothermal efficiency of 90%. [Display omitted] • A study is performed on 4 ANG reactor configurations, including radiative effect. • An optimization study is carried out on ANG reactors with fins. • An improvement of 33% in storage capacity is obtained compared to adiabatic case. • Annular reactor outperformed others in terms of volumetric storage capacity. • An isothermal efficiency of more than 90% is obtained with annular finned reactor. [ABSTRACT FROM AUTHOR]