Temperature Polarization Coefficients in Membrane Distillation

Velázquez, A.; Mengual, J.I.

doi:10.1021/ie00041a019

Cited by 35 publications

(10 citation statements)

References 9 publications

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“…Eq. (13), which is based on heat transfer experiments including free convection, was expected to augment the heat fluxes. However, in this case, according to the analysis performed in Refs.…”

Section: Resultsmentioning

confidence: 99%

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Heat and mass transfer in vacuum membrane distillation

Mengual

Khayet

Godino

2004

International Journal of Heat and Mass Transfer

249

129

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Section: Resultsmentioning

confidence: 99%

“…This is due to the decrease of the temperature polarisation effects. The contribution of the boundary layers to the decrease of the thermal effects in MD has been studied extensively [1][2][3][4][5][7][8][9][10][11][12][13]. The method proposed is based on the fact that the thickness of the boundary layer decreases with the flow rate (i.e.…”

Section: Theorymentioning

confidence: 99%

Heat and mass transfer in vacuum membrane distillation

Mengual

Khayet

Godino

2004

International Journal of Heat and Mass Transfer

249

129

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“…The phenomenon of evaporation at the feed-membrane interface and condensation at the permeate-membrane interface creates a temperature gradient with the bulk solution. Temperature polarization (TP) is a condition when the temperature at the membrane interface differs from its bulk solution [26][27][28]. TP is considered a critical factor that impacts the vapor flux of an MD system.…”

Section: Temperature Polarizationmentioning

confidence: 99%

Desalination by Membrane Distillation

Mustakeem¹,

Soukane²,

Nawaz³

et al. 2022

Distillation Processes - From Solar and Membrane Distillation to Reactive Distillation Modelling, Simulation and Optimization

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At present, around 25% of water desalination processes are based on distillation. Similar to classical distillation, membrane distillation is a phased-change process in which a hydrophobic membrane separates two phases. Membrane distillation is considered an emerging player in the desalination, food processing and water treatment market. Due to its high salt rejection, less fouling propensity, operating at moderate temperature and pressure, membrane distillation is considered as a future sustainable desalination technology. The distillation process is quite well known in desalination. However, membrane distillation emerged a few decades ago, and a thorough understanding is needed to adapt this technique in the near future. This review chapter introduces the classical distillation and membrane distillation as an emerging technology in the desalination arena. Heat and mass transfer and thermodynamics in membrane distillation, characteristics of the performance metrics of membrane distillation are also described. Finally, the performance evaluation of MD is presented. The possibility of using low-grade heat in membrane distillation allows it to integrate directly to solar energy and industrial waste heat.

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“…In particular, for the case of MD, Velázquez and Mengual [21] carried out experiments to evaluate the temperature polarization coefficient in spacer-filled channels. Martinez-Diez et al [22] and Yun et al [23] stated that coarser spacers with thicker filaments perform better in reducing polarization and enhancing mass flux.…”

Section: Literature Reviewmentioning

confidence: 99%

Performance comparison between overlapped and woven spacers for membrane distillation

Gurreri¹,

Tamburini²,

Cipollina³

et al. 2017

dwt

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a b s t r a c tThe sustainable production of freshwater from seawater desalination is receiving increasing attention. Recently, some desalination technologies are taking advantage from the coupling with renewable resources; among them, membrane distillation (MD) is one of the most promising since it can be easily powered by low-grade thermal energy. MD being an emerging technology, efforts are required to optimize geometry and operating conditions of real units in order to reduce the unitary freshwater production cost. In particular, temperature polarization is a well-known detrimental effect for the process driving force; spacers are traditionally used to enhance mixing and make temperature boundary layers thinner, at the cost of higher pressure losses. The present work is devoted to testing and comparing the performance of two different two-layer net spacers: overlapped and woven. Investigations were carried out both by experiments and by computational fluid dynamics (CFD) at different Reynolds numbers, ranging from creeping flow to turbulent flow regimes. Experiments (for intermediate to high Re) made use of thermochromic liquid crystals along with digital image processing. Computational results (for low to intermediate Re) were obtained via steady state (low Re) or direct numerical simulations (intermediate Re) along with the unit cell approach. A good agreement between experiments and CFD results was obtained in the range of superposition. Results showed that woven spacers guarantee a better mixing than overlapped ones, especially in the low to intermediate Re range, thus resulting in Nusselt numbers 2.5-3 times higher. On the other hand, the less disturbed flow field induced by overlapped spacers was found to yield friction coefficients up to 4 times lower, thus allowing lower pumping costs. The choice between the two configurations depends crucially on the relative importance attributed to savings in membrane surface area and in pumping energy for any specific application.

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Temperature Polarization Coefficients in Membrane Distillation

Cited by 35 publications

References 9 publications

Heat and mass transfer in vacuum membrane distillation

Heat and mass transfer in vacuum membrane distillation

Desalination by Membrane Distillation

Performance comparison between overlapped and woven spacers for membrane distillation

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