Browsing by Author "Bandara, R.M.P.S."

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Computational Modelling of Drying Process in a Novel Solar Dryer Design with Experimental Validation
(SLIIT, Faculty of Engineering, 2024-10) Gunathilaka, R.A.C.K.; Kumar, R; Chatterjee, S; Bandara, R.M.P.S.
Crops and food products are dried by a variety of conventional methods, including open-air drying, smoking, and oven-drying for preservation purposes. Due to inherent drawbacks in the conventional drying methods, such as higher energy consumption, possible contamination and uncontrollable drying conditions, solar drying is preferred over the said drying methods. A solar dryer utilizes solar energy to dry crops, food products etc. by harnessing the heat energy from the sun to reduce the moisture content of the substances. The study focuses on modelling the drying process in an indirect type novel solar dryer through computational modelling with subsequent experimental validation of the temperature and air velocity profiles. The solar dryer is comprised of a divergent section, a convergent section, an absorber plate, a drying chamber, an outlet and trays. The Computational Fluid Dynamics (CFD) approach has been adopted in modelling the drying process and ANSYS Fluent has been used as the CFD tool. The computational mesh is comprised of 621,106 tetrahedral mesh elements. Pressurevelocity- coupling numerical scheme was used for discretizing the Navier-Stokes and other transport equations. A realizable k-ε model was applied in modelling turbulence. CFD simulations were conducted for three different mass flow rates of air: 0.0872 kg/s, 0.0636 kg/s, and 0.0447 kg/s at a solar insolation of 996 W/m². CFD simulations provided a comprehensive insight into the temperature and velocity profiles within the solar dryer. Furthermore, modelling results are well aligned with the experimental measurements taken on the solar dryer, confirming the reliability and accuracy of the computational model. The findings of this study will contribute as a platform for optimizing the performance of solar dryer designs.
Open Access
Efficient Ventilation Configurations for an Isolation Ward in View of Reducing the Potential Contamination of Its Occupants
(SLIIT, Faculty of Engineering, 2023-03-02) Durage, H; Attalage, R; Bandara, R.M.P.S.
The rise of respiratory infections, such as the SARS epidemic in 2003, and the H1N1 influenza epidemic in 2011, highlighted the importance of efficient ventilation in healthcare facilities. The novel SARS -Cov-2 disease has sparked many concerns over the ventilation performance of multi-bed isolation wards and their ability to suppress airborne infectious contamination. The study is primarily based on suggesting ventilation improvements for a locally acquired multi-bed intensive care isolation unit. The study via ANSYS -fluent incorporates a k-𝜀 turbulent model that is used to analyze exhaled CO2 particle tracks of 4 human models. Three ventilation strategies, namely, Displacement, Stratum, and Curtain -Air-jet are initially considered and evaluated based on two indoor air quality indices (IAQs), namely, air change efficiency and contaminant removal effectiveness. Stratum ventilation comfortably exhibits unidirectional flow characteristics with an air change efficiency of 0.946, which was obtained through ANSYS -CFX while each suggested configuration is capable of achieving a contaminant removal effectiveness value greater than 1 which depicts that the contamination source is not in a perfect mixing zone. Results provided inconclusive evidence to draw correlations between the two IAQ indices and thus it is confirmed that these indices solely depend on the type of ventilation strategy. Contaminant concentration on health care worker breathing plane and exhaled particle tracking for 4 minutes in each analyzed configuration revealed that both Stratum and Curtain air-jet models improve the escaped particle efficiency by 25% and 29% respectively compared to the base model. These models are further compared against reference values specified by guidelines to evaluate their suitability for real-world operation.