Mathematical Modelling of CP and Scaling in Roto-dynamic RO System at Seawater Salinity During Laminar and Turbulent Cross Flow.
ORAL
Abstract
Concentration polarization (CP) and scaling are critical challenges in reverse osmosis (RO) systems, particularly in brackish and seawater desalination. CP occurs when solutes accumulate near the membrane surface, increasing osmotic pressure and reducing permeate flux, while scaling, such as gypsum deposition, leads to membrane fouling and a decline in system performance. These phenomena significantly hinder the efficiency of RO systems, increasing operational costs and maintenance efforts. Addressing these issues is essential for improving the sustainability and reliability of desalination technologies.
The present study focuses on understanding the effects of induced shear stress and enhanced flow dynamics on CP and gypsum scaling in an RO module, with a specific emphasis on the transition from laminar to turbulent flow regimes. Through the use of computational fluid dynamics (CFD), we developed a numerical model that simulates salt rejection and scaling behavior at seawater salinity levels. Our model integrates the Reynolds Stress Model (RSM) to capture the complex flow dynamics associated with turbulent regimes, and an eddy viscosity-dependent eddy diffusivity model to represent salt transport over the membrane surface.
The simulation results indicate that the shift to turbulent flow conditions leads to a significant reduction in CP. Enhanced mixing and higher shear rates disrupt the concentration boundary layer, facilitating better mass transfer and reducing solute accumulation near the membrane surface. Consequently, the reduction in CP also mitigates gypsum scaling and fouling, improving the membrane's lifespan and overall performance of the RO system. The findings suggest that inducing turbulence within the RO module can play a key role in optimizing system efficiency, extending membrane life, and reducing maintenance costs.
This study offers valuable insights into the design and operation of more efficient RO systems by demonstrating the benefits of turbulent flow in mitigating the adverse effects of CP and scaling. These results contribute to the advancement of desalination technology, promoting more reliable and sustainable freshwater production solutions in regions affected by water scarcity.
The present study focuses on understanding the effects of induced shear stress and enhanced flow dynamics on CP and gypsum scaling in an RO module, with a specific emphasis on the transition from laminar to turbulent flow regimes. Through the use of computational fluid dynamics (CFD), we developed a numerical model that simulates salt rejection and scaling behavior at seawater salinity levels. Our model integrates the Reynolds Stress Model (RSM) to capture the complex flow dynamics associated with turbulent regimes, and an eddy viscosity-dependent eddy diffusivity model to represent salt transport over the membrane surface.
The simulation results indicate that the shift to turbulent flow conditions leads to a significant reduction in CP. Enhanced mixing and higher shear rates disrupt the concentration boundary layer, facilitating better mass transfer and reducing solute accumulation near the membrane surface. Consequently, the reduction in CP also mitigates gypsum scaling and fouling, improving the membrane's lifespan and overall performance of the RO system. The findings suggest that inducing turbulence within the RO module can play a key role in optimizing system efficiency, extending membrane life, and reducing maintenance costs.
This study offers valuable insights into the design and operation of more efficient RO systems by demonstrating the benefits of turbulent flow in mitigating the adverse effects of CP and scaling. These results contribute to the advancement of desalination technology, promoting more reliable and sustainable freshwater production solutions in regions affected by water scarcity.
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Publication: 1. N Prakash, A Chaudhuri, S.P Das, Numerical modelling and analysis of concentration polarization and scaling of gypsum over the RO membrane during sea water desalination, Chemical Engineering Research and Design, Doi: https://doi.org/10.1016/j.cherd.2022.12.050.<br><br>2. Uppu, A. Chaudhuri, S.P. Das, N. Prakash, CFD modelling of Gypsum scaling in cross-flow RO filters using moments of particle population balance, Doi: HTTPs: //doi.org/10.1016/j.jece.2020.104151
Presenters
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Nitikesh Prakash
Indian Institute of Technology Madras
Authors
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Nitikesh Prakash
Indian Institute of Technology Madras