Computational fluid dynamic study on adsorption-based desalination and cooling systems with stepwise porosity distribution

Abstract

Adsorption desalination (AD) is a promising alternative desalination technology with low energy cost. Conventional studies about AD cycle are mainly based on lumped models that do not involve the details of heat and mass transfer characteristics. In this study, a comprehensive analysis about the effect of stepwise porosity distributions inside a finned-tube bed on system performance is conducted with a transient computational fluid dynamic (CFD) model which captures the bed spatial temperature and pressure distributions, thus to reveal the heat and mass transfer mechanisms. Various bed porosity distribution scenarios at different packed directions are considered. Results reveal that all the forward distributions show an advanced cooling as well as water production. D3-F distribution results in the maximum specific cooling power (SCP) and specific daily water production (SDWP), presenting a 16.2% improvement over that of the uniform at the fin pitch of 55 mm. Moreover, system performances under various operating conditions including ad/desorption time, switch time and heating source temperature are evaluated. The system performance under optimal bed porosity distribution is tested with several adsorbents, among which silica gel of RD type shows a maximum cooling effect of 0.219 kW/kg and water throughput of 7.5 m3/ton-day.