A CFD study of heat transfer through spacer channels of membrane distillation modules

Shakaib, M.; Hasani, S. M. F.; Haque, M. Ehtesham-ul; Ahmed, Iqbal; Yunus, Rosli Mohd

doi:10.1080/19443994.2013.789234

Cited by 27 publications

(12 citation statements)

References 31 publications

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“…Later on, the interest in dynamic modeling for the MD process continued, and followed with many studies that tackled the dynamic analysis of heat and mass transfer using Computational Fluid Dynamics (CFD) techniques [30][31][32][33][34]. For more numerical models for the MD process see [35][36][37][38][39][40] Literature models offer a predictive estimation for the temperature of the boundary layer region of the membrane, however they are unable to provide information about the temperature of the bulk solutions in the feed and the permeate sides. Additionally, the steady state models do not count for the time evolution of the process, and the needs of the intermittent sources, therefore they can not capture any sudden changes which might happen to the process.…”

Section: Heat Transfermentioning

confidence: 99%

Dynamic modeling and experimental validation for direct contact membrane distillation (DCMD) process

et al. 2016

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This work proposes a mathematical dynamic model for the direct contact membrane distillation (DCMD) process. The model is based on a 2D Advection-Diffusion Equation (ADE), which describes the heat and mass transfer mechanisms that take place inside the DCMD module. The model studies the behavior of the process in the time varying and the steady state phases, contributing to understanding the process performance, especially when it is driven by intermittent energy supply, such as the solar energy. The model is experimentally validated in the steady state phase, where the permeate flux is measured for different feed inlet temperatures and the maximum absolute error recorded is 2.78• C. Moreover, experimental validation includes the time variation phase, where the feed inlet temperature ranges from 30• C to 75• C with 0.1 • C increment every 2 minutes. The validation marks relative error to be less than 5%, which leads to a strong correlation between the model predictions and the experiments.

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Section: Heat Transfermentioning

confidence: 99%

Dynamic modeling and experimental validation for direct contact membrane distillation (DCMD) process

et al. 2016

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“…The first one considers only the feed side of the module while the second is a conjugate approach that includes both the feed and the permeate sides. Regarding the first approach, models evolved from simple boundary conditions setting constant values for the permeate flux [26], or the heat flux [16,27], or the membrane mass transfer coefficient [28,29] to more complex formulations coupling to the module scale both heat and species transport across the membrane [30]. The second approach has often been used to circumvent the complexity of the strongly non-linear boundary condition at the membrane permeate interface, leaving to the CFD code the calculation of the temperature at the permeate side of the membrane surface.…”

Section: Introductionmentioning

confidence: 99%

Direct contact membrane distillation module scale-up calculations: Choosing between convective and conjugate approaches

Soukane

Lee

Ghaffour

2019

Separation and Purification Technology

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Membrane distillation (MD) process technology is swiftly moving to industrial prototyping where efficient scale-up calculations are crucial to shorten product development cycle. The aim of this numerical investigation is to suggest the best modeling strategy that will enable to innovate; modify or check new direct contact MD (DCMD) module designs or operation in a timely manner. Two main modeling strategies are presented, namely convective and conjugate approaches. For a given flat module, it is shown that replacing the permeate side by a modified convection boundary condition that accounts for every known resistance to heat transfer gives similar results in the feed side as a coupled conjugate approach where the membrane, with a modified thermal conductivity, is part of the computational domain. The two methods are compared for different module lengths in terms of permeate flux and temperature distribution.Simulation time reports show the important gain in CPU time when using the convective approach while retaining desired calculation accuracy during scale-up. Furthermore, investigations were carried out to assess the effect of 3D inlet and outlet effects. Results for a laboratory scale module suggest that the convective approach can be safely used during early design stages and scale-up of single modules in the range of high permeate fluxes, while the conjugate approach has to be used for an accurate prediction of permeate temperatures needed in heat recovery strategy and equipment design. Highlights Conjugate vs convective CFD modeling is implemented and compared for DCMD  Temperature and permeate flux distribution for several module lengths is studied  The convective approach is less CPU demanding  The convective approach can be used safely for early DCMD module design  The conjugate approach need to be used for overall DCMD module operation

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“…This effectively reduces the mass transfer resistance associated with the air gap, which tends to increase permeate production rate, while the heat transfer resistance of the gap is also reduced, leading to higher heat conduction loss across the membrane, larger temperature polarization in the channels, and lower thermal efficiency [49]. Since thermal bridging is unsteady and localized, it cannot be readily modelled in typical 1-D numerical models [50]. Forced flooding occurs when the permeate fills air gap, and can be caused by small gap size (where it fills to quickly to drain) or hydrostatically with a drain point above the active membrane area [51].…”

Section: Introductionmentioning

confidence: 99%

Comprehensive condensation flow regimes in air gap membrane distillation: Visualization and energy efficiency

Warsinger

Swaminathan

Morales

et al. 2018

Journal of Membrane Science

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The thermal performance of air gap membrane distillation (AGMD) desalination is dominated by heat and mass transfer across the air gap between the membrane and the condensing surface. However, little is known about the impact of condensate flow patterns in some design variations of the air gap. In this study, air gap membrane distillation experiments were performed at various inlet temperatures, varying module inclination angle, condensing surface hydrophobicity, and gap spacer design to identify the effect of each on the permeate production rate and thermal efficiency of the system. Energy efficiency modeling was performed as well. Additionally, this study is one of the first with enhanced visualization of flow patterns within the air gap itself, by using a transparent, high thermal conductivity sapphire plate as the condenser surface. System-level numerical modeling is used to further understand the impact of these flow regimes on overall energy efficiency, including flux and GOR. A brief review of membrane distillation condensation regimes is provided as well. For tilting the AGMD flat-plate module, permeate flux was barely influenced except at extreme positive angles (>80ᵒ), and moderate negative angles (<-30ᵒ), where condensate fell onto the membrane surface. The surface with the hydrophobic coating (for dropwise condensation) was shown to have better droplet shedding (with very small nearly spherical droplets) and fewer droplets bridging the gap. Superhydrophobic surfaces (for jumping droplet condensation) were similar, with much smaller droplet sizes. Meanwhile, the hydrophilic surface for small gap sizes (< 3 mm) often had pinned regions of water around the hydrophilic surface and plastic spacer. Overall, the various results imply that the common assumption of a laminar condensate film poorly describes the flow patterns in real systems for all tilt angles and most spacer designs. Real system performance is likely to be between that of pure AGMD and permeate gap membrane distillation (PGMD) variants, and modeling shows that better condensing in air gaps may improve system energy efficiency significantly, with strong relative advantages at high salinity.

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A CFD study of heat transfer through spacer channels of membrane distillation modules

Cited by 27 publications

References 31 publications

Dynamic modeling and experimental validation for direct contact membrane distillation (DCMD) process

Dynamic modeling and experimental validation for direct contact membrane distillation (DCMD) process

Direct contact membrane distillation module scale-up calculations: Choosing between convective and conjugate approaches

Comprehensive condensation flow regimes in air gap membrane distillation: Visualization and energy efficiency

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