Non-equilibrium numerical modelling of finned tube heat exchanger for adsorption desalination/cooling system using segregated solution approach

A transient two-dimensional local non-equilibrium model for finned tube adsorber bed in adsorption cooling/desalination system has been numerically developed, including internal and external heat and mass resistances. The numerical model uses the segregated solution approach to solve the coupled partial differential equations, which offers effective computational solution for such complex problem where only 16.2 s were required to get the results of one cycle (adsorption and desorption). This model predicts the spatial and time variation of vapor and adsorbent material temperatures, vapor pressure and water uptake throughout the adsorbent material are predicted which allows effective use of the adsorbent material. The model was validated using published experimental data for silica gel/water adsorption process showing maximum deviation of 5% in average temperature. The validated model was used to investigate the effects of fin height, fin spacing and tube diameter on the Specific Cooling Power (SCP) and Specific Daily Water Production (SDWP) using silica gel. Results showed that decreasing the fin height results in improving the SCP and SDWP significantly to reach maximum values of 1.3226 kW/kg and 23L/kg/day at fin height of 5 mm. Also reducing fin spacing from 11.5 mm to 3.6 mm improves the SCP and SDWP by around 25%.