Gradient porosity distribution of adsorbent bed for efficient adsorption cooling.

• Impacts of the spatial gradient porosity distribution on the cooling performance are explored. • Different stepwise and continuous polynomial distributions of bed porosity are investigated. • The cooling performance is pointedly impacted by the spatial porosity distribution in the z-direction. • SCP under the S1 porosity distribution at 600 s is augmented by 9.5% (0.348 kW/kg). Adsorption cooling is an emerging, environment-friendly and energy-saving refrigeration technology. In conventional studies, the spatial distribution of the porosity of the adsorbent bed has never been considered, which could impact the heat and mass transfer in adsorption process, thus the cooling performance of the adsorption cooling systems. Here the influence of the spatial gradient porosity distribution (stepwise and continuous polynomial distributions) of the adsorbent bed on the adsorption process and cooling performance is systematically explored with average bed porosity kept constant. Results reveal that the cooling performance is significantly impacted by the spatial porosity distribution in the z direction. Provided the bed porosity increases from the cooling side to the steam side, the overall heat transfer performance is improved, which reduces the adsorption temperature that contributes to the adsorption uptake and the specific cooling power (SCP). Under the continuous polynomial distribution of the bed porosity, a SCP of 0.348 kW kg−1 is obtained, 9.5% larger than that under the uniform distribution of the bed porosity. A desired bed porosity distribution of the adsorbent bed is that the porosity gradient increases from the cooling side to the steam side. [ABSTRACT FROM AUTHOR]