Gas and vapour transport through microporous membranes. II. Membrane distillation

Schofield, R.W.; Fane, Anthony G.; Fell, C.J.D.

doi:10.1016/0376-7388(90)80012-b

Cited by 186 publications

(98 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The porosity of the membrane active layer was 92.5±0.5% measured by a wetting method [17]. The measured Liquid Entry Pressure (LEP) using the method provide in [16] was 80±5 kPa, the contact angle was 140±2.5° measured by the method described in [16] and the calculated tortuosity in [17] was 1.10 which is similar to available data [18,19]. The channel was filled with a spacer as described in [14].…”

Section: Theory and Mathematical Modellingsupporting

confidence: 70%

Predicting the influence of operating conditions on DCMD flux and thermal efficiency for incompressible and compressible membrane systems

Zhang

Gray

2013

Desalination

View full text Add to dashboard Cite

Membrane distillation (MD) is a hybrid of thermal distillation and membrane separation. As a thermal distillation process, MD is an energy intensive technique. Therefore, it is important to select optimum operation parameters to maximise both the flux and energy efficiency, even though low grade or waste heat maybe employed in the process. In this paper, a model originally developed for Direct Contact Membrane Distillation (DCMD) using a compressible membrane is employed to predict the thermal efficiency and flux for both compressible and incompressible membrane systems. The predicted thermal efficiency was also compared with experimental results, and the errors were mostly within the range of experimental variation (±5%). As a result of membrane compressibility, the thermal conductivity and vapour permeability of the membrane were altered, causing a change in flux and energy efficiency. If a compressible membrane is used, it was found from the predicted results, that increasing stream velocity will reduce the thermal efficiency and even reduce flux once the increased pressure associated with the higher flows is in the range to compress the membrane. Increasing temperature either on feed side or on permeate side will increase thermal efficiency. In scaling up the process using a compressible membrane, it is necessary to reduce the pressure drop across the module in the DCMD process to maximise energy efficiency and flux. Since the operating temperature is normally not adjustable when low grade waste heat is employed, optimising the flowrates and pressure drops are the key factors for optimising flux and thermal efficiency.

show abstract

Section: Theory and Mathematical Modellingsupporting

confidence: 70%

Predicting the influence of operating conditions on DCMD flux and thermal efficiency for incompressible and compressible membrane systems

Zhang

Gray

2013

Desalination

View full text Add to dashboard Cite

show abstract

“…(3) and (7), when using N 2 as the sweeping gas, the humidity ratio can be written as (8) As a result, the vapor partial pressure on the gas side (i.e. permeate side) can be expressed as (9) Similarly, when using air as the sweeping gas, (10) In reality, the vapor partial pressure, humidity ratio and permeate flux associated with the temperature along the membrane surface are not homogenous. In modelling, however, these parameters are often supposed to change homogenously along the membrane based on a series of assumptions [18,19].…”

Section: Relationships Between Vapor Flux Vapor Pressure and Temperamentioning

confidence: 99%

“…K n <0.01), molecule-molecule collisions become more significant and the mass transfer resistance is caused by the stagnant air trapped within the membrane pore. In this case, water vapor flux can be described by molecule diffusion [4,10,18]: (18) with (19) where D M is the molecular diffusion coefficient, P air-lm is the logarithmic mean pressure of air, D is the water vapor diffusion coefficient and P is the total pressure inside the membrane pore.…”

Section: Mass Transfer Mechanisms Through a Porous Membranementioning

confidence: 99%

See 1 more Smart Citation

Condensation studies in membrane evaporation and sweeping gas membrane distillation

Zhao

Feron

Xie

et al. 2014

Journal of Membrane Science

View full text Add to dashboard Cite

Vapor transfer is an important phenomenon in various thermally driven membrane processes such as membrane distillation (MD), membrane evaporation and membrane condensation. In this study, we explore the mass transfer phenomena in sweeping gas membrane distillation (SGMD) by systematically investigating the effects of operational parameters on the process performance. It is found that mass transfer in SGMD is principally determined by both the evaporation temperature and the sweeping gas flow rate, and is significantly influenced by the operational parameters (i.e. fluid velocities) through multiple effects, including the boundary layer effect on both sides of the membrane, and the temperature polarization effect. We also prove that at low gas flow rates (i.e. insufficient gas vapor-holding capacity) the sweeping gas becomes saturated and water vapor forms droplets due to condensation on the gas side of the membrane. To the best of our knowledge, this is the first study reporting the interesting mass transfer phenomena in terms of vapor condensation and droplet re-evaporation in SGMD, which are of great significance for the heat and mass transfer in many thermally driven membrane processes using stripping gas.

show abstract

“…The total pressure is constant at atmospheric leading to negligible viscous kind of flow [10], [13], [14]. Knudsen number is expressed as; (7a) where is the mean free path of the water molecule and is the pore size (diameter).…”

Section: B Membrane Permeability ( )mentioning

confidence: 99%

Flux Prediction in Direct Contact Membrane Distillation

Lawal¹,

Khalifa²

2014

IJMMM

View full text Add to dashboard Cite

Abstract-Membrane distillation (MD) is a potential mean of water desalination. MD is a thermally driven desalination technology that has been employed in four basic configurations. One of these configuration is Direct Contact Membrane Distillation (DCMD). In DCMD, both hot and cold solution is maintained in direct contact with micro porous hydrophobic membrane material. Heat and mass transfer analysis was performed on DCMD. Based on Kinetic theory of gas, the performance of different models of membrane permeability (coefficient) was investigated under different DCMD operating parameters (feed temperature, coolant temperature and feed flow rate). Knudsen number provides the guideline in identifying the type of model of mass transfer to be considered under any given experimental conditions.Results revealed that for a given pore size under the same simulation and experimental conditions, Transition (KnudsenMolecular diffusion) type of flow model predictions is in good agreement with the experimental results. Hence the best model to be consider for flux prediction in DCMD. The effect of membrane pore size was also studied. Results showed that permeate flux increases with increase in pore size up to the critical pore condition where the flux prediction remain constant (unchanged).Index Terms-Desalination, direct contact membrane distillation, flux prediction, hydrophobic membrane material.

show abstract

Gas and vapour transport through microporous membranes. II. Membrane distillation

Cited by 186 publications

References 7 publications

Predicting the influence of operating conditions on DCMD flux and thermal efficiency for incompressible and compressible membrane systems

Predicting the influence of operating conditions on DCMD flux and thermal efficiency for incompressible and compressible membrane systems

Condensation studies in membrane evaporation and sweeping gas membrane distillation

Flux Prediction in Direct Contact Membrane Distillation

Contact Info

Product

Resources

About