The Effect of Module Geometry on Heat and Mass Transfer in Membrane Distillation

2016 ◽  
Vol 11 (1) ◽  
pp. 35-39 ◽  
Author(s):  
Hossein Ahadi ◽  
Javad Karimi-Sabet ◽  
Mojtaba Shariaty-Niassar
Keyword(s):  
Fluid Dynamic ◽  
Membrane Distillation ◽  
Dynamic Simulations ◽  
Vapor Flux ◽  
Membrane Pores ◽  
Average Temperature ◽  
Temperature Polarization ◽  
Flat Sheet Membrane ◽  
Module Geometry ◽  
Module Performance

Abstract Some features of Direct Contact Membrane Distillation (DCMD), as one of the interesting membrane processes, has been studied in this effort. 3D computational fluid dynamic simulations were carried out to investigate some geometric parameter effects on flat sheet membrane module performance. It is obvious that using of baffles could noticeably improve the performance of the system. Hence, in present work, some baffle configurations were simulated and some parameters like temperature polarization, vapor flux and pressure drop through module length were investigated. The Simulation was performed based on neglecting viscous flow in membrane pores and dusty gas model was applied to predict vapor flux through membrane. Simulation results predicted that by using the new configuration we could have 40–60% vapor flux improvement (depend on inflow velocity) compared to a module without baffle. It was found that the average temperature polarization (TP), as a proper criteria, was higher for baffled one in all situations.

Channel Length Influence on the Performance of the Vacuum Membrane Distillation

2020 ◽  
Author(s):  
Abdulaziz M. Alasiri ◽  
Umar Alqsair ◽  
Sertac Cosman ◽  
Robert Krysko ◽  
Alparslan Oztekin
Keyword(s):  
Membrane Surface ◽  
Membrane Distillation ◽  
Channel Length ◽  
Water Vapor Transport ◽  
Membrane Thickness ◽  
Local Concentration ◽  
Permeate Flux ◽  
Hydrophobic Membrane ◽  
Vapor Flux ◽  
Temperature Polarization

Abstract The demand for freshwater has been increased globally. Membrane distillation (MD) technique can be an attractive option for desalination applications. MD is defined as a thermal-driven separation process that implements a hydrophobic membrane for allowing only water vapor transport through the membrane. VMD system is investigated in this study to examine its sensitivity toward the channel design. PTFE membrane is employed and treated as a functional surface where its main properties, such as porosity, tortuosity, pore diameter, and membrane thickness are defined. Different flow rates and inlet temperatures of the feed solution are involved to intensely study the effect of the channel length on VMD performance. The local concentration and temperature polarization coefficient and mass flux along the membrane surface are presented and discussed. With the increasing length of the module, concentration and temperature polarization levels are increased, and the vapor flux is decreased. It is shown that the permeate flux decreases linearly with the channel length. The slope of the permeate flux with length can be used to estimate the flux performance of modules with varying length.

Dynamic Simulations of Alumina Membrane Fouling From Recycling of Semisynthetic Metalworking Fluids

2008 ◽  
Vol 130 (6) ◽  
Author(s):  
John E. Wentz ◽  
Shiv G. Kapoor ◽  
Richard E. DeVor ◽  
N. Rajagopalan
Keyword(s):  
Membrane Fouling ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Metalworking Fluids ◽  
Alumina Membrane ◽  
Dynamic Simulations ◽  
Membrane Pores ◽  
Alumina Membranes ◽  
Membrane Flux ◽  
Partial Blocking

The recycling of semisynthetic metalworking fluids (MWFs) using alumina membranes is significantly impacted by aggregated MWF microemulsions that cause partial and complete blocking of membrane pores. In this paper, computational fluid dynamic methods are employed to model both a portion of a sintered alumina membrane with tortuous pores and the microemulsions passing through it. Several particle size distributions, measured experimentally at various times through the membrane service life and under two different cross-flow velocities, were used to determine the particle sizes simulated in the flow. Simulated MWF particles smaller than the largest pore diameter were found to completely block the pore through the build-up of a network of particles that blocked smaller diameter inlets and outlets. The results demonstrate as well that significant membrane flux reduction can occur by partial blocking of pore inlets and outlets even in the absence of complete blocking.

The Effect of Turbulence Promoters on Vacuum Membrane Distillation Module Performance

2020 ◽  
Author(s):  
Robert Krysko ◽  
Abdulaziz M. Alasiri ◽  
Umar Alqsair ◽  
Sertac Cosman ◽  
Alparslan Oztekin
Keyword(s):  
Pressure Drop ◽  
Concentration Polarization ◽  
Performance Enhancement ◽  
Fluid Dynamic ◽  
Membrane Distillation ◽  
Membrane Properties ◽  
Significant Finding ◽  
Dynamic Simulations ◽  
Baseline Design ◽  
Polarization Coefficient

Abstract Computational fluid dynamic simulations are conducted to compare the performance of three proposed VMD module designs. Key parameters, including concentration polarization coefficient (CPC), temperature polarization coefficient (TPC), mass flux, and module pressure drop, are evaluated to analyze flux performance and membrane wetting implications. The CFD simulations are conducted on a three-dimensional domain for each design with representative membrane properties. The Reynolds numbers evaluated are 500 and 1500. Contour plots are provided to gain insight into the flow-field characteristics. Stream-wise profiles and average values are provided as a means to compare the design performance. The results indicate that adding either net-type spacers or membrane corrugation to the feed channel provides performance enhancement over an empty channel design. It is found that both the net-type spacer concept and the corrugated membrane offer better flux performance over the baseline design (49%–60% for the net-type spacers and 62%–67% flux enhancement for the corrugated membrane), reduced concentration polarization coefficient (51% for the Re = 500 case and 45% for the Re = 1500 case for spacers and 58% for the Re = 500 case and 49% for the Re = 1500 case for corrugation), increased TPC (2%–3% higher), and increased wall shear stress over the baseline design. The most significant finding is that the corrugated membrane design accomplishes the listed performance improvement while yielding five times less pressure drop increase than the net-type spacer design.

The Effect of Mixing Promotors on Sweeping Gas Membrane Distillation System Performance

2019 ◽  
Author(s):  
Umar F. Alqsair ◽  
Anas M. Alwatban ◽  
Ahmed M. Alshwairekh ◽  
Robert Krysko ◽  
Abdullah A. Alghafis ◽  
...  
Keyword(s):  
Flow Rate ◽  
Membrane Distillation ◽  
Membrane Properties ◽  
Functional Surface ◽  
Feed Concentration ◽  
Turbulent Structures ◽  
Vapor Flux ◽  
Temperature Polarization ◽  
Dynamics Simulations ◽  
Sweeping Gas

Abstract Computational fluid dynamics simulations were conducted to model the effect of adding mixing promoters in sweeping gas membrane distillation modules. Net-type spacers of 45° are placed in the feed side while membrane corrugation is employed with the tips of the corrugation pointing towards the permeate side. The membrane corrugation is of chevron type. The membrane is considered as a functional surface, and the vapor flux through the membrane is modeled using the Dusty-Gas model. The vapor flux equation couples the vapor pressure variation across the membrane with the feed concentration. The flow inside the channels with mixing promoters is considered turbulent. The k–ω SST turbulent model is used to model the steady-state turbulent structures inside the channels. The flow rate in the feed side is fixed, and the flow rate in the permeate channel is varied so that Rep = 1000,1500, and 2000 are considered. The inlet feed and permeate temperatures, and the membrane properties are fixed. The results indicate that the presence of mixing promoters increases the vapor permeation through the membrane by alleviation of the concentration and temperature polarization effects. The mixing promoters are more effective at high flow rates in both channels.

Towards real-time fire data synthesis using numerical simulations

2021 ◽  
pp. 073490412199344
Author(s):  
Wolfram Jahn ◽  
Frane Sazunic ◽  
Carlos Sing-Long
Keyword(s):  
Real Time ◽  
Computational Fluid Dynamic ◽  
Dynamic Models ◽  
Fluid Dynamic ◽  
Near Field ◽  
Computing Time ◽  
Temperature Correction ◽  
Dynamic Simulations ◽  
Conservation Of Energy ◽  
Fire Scenarios

Synthesising data from fire scenarios using fire simulations requires iterative running of these simulations. For real-time synthesising, faster-than-real-time simulations are thus necessary. In this article, different model types are assessed according to their complexity to determine the trade-off between the accuracy of the output and the required computing time. A threshold grid size for real-time computational fluid dynamic simulations is identified, and the implications of simplifying existing field fire models by turning off sub-models are assessed. In addition, a temperature correction for two zone models based on the conservation of energy of the hot layer is introduced, to account for spatial variations of temperature in the near field of the fire. The main conclusions are that real-time fire simulations with spatial resolution are possible and that it is not necessary to solve all fine-scale physics to reproduce temperature measurements accurately. There remains, however, a gap in performance between computational fluid dynamic models and zone models that must be explored to achieve faster-than-real-time fire simulations.

scholarly journals Analysis of Radial Inflow Turbine Losses Operating with Supercritical Carbon Dioxide

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3561
Author(s):  
Antti Uusitalo ◽  
Aki Grönman
Keyword(s):  
Fluid Dynamic ◽  
Dynamic Simulations ◽  
Average Deviation ◽  
Loss Analysis ◽  
Specific Speed ◽  
Loss Models ◽  
Rotor Losses ◽  
Radial Turbines ◽  
Design Power ◽  
Good Agreement

The losses of supercritical CO2 radial turbines with design power scales of about 1 MW were investigated by using computational fluid dynamic simulations. The simulation results were compared with loss predictions from enthalpy loss correlations. The aim of the study was to investigate how the expansion losses are divided between the stator and rotor as well as to compare the loss predictions obtained with the different methods for turbine designs with varying specific speeds. It was observed that a reasonably good agreement between the 1D loss correlations and computational fluid dynamics results can be obtained by using a suitable set of loss correlations. The use of different passage loss models led to high deviations in the predicted rotor losses, especially with turbine designs having the highest or lowest specific speeds. The best agreement in respect to CFD results with the average deviation of less than 10% was found when using the CETI passage loss model. In addition, the other investigated passage loss models provided relatively good agreement for some of the analyzed turbine designs, but the deviations were higher when considering the full specific speed range that was investigated. The stator loss analysis revealed that despite some differences in the predicted losses between the methods, a similar trend in the development of the losses was observed as the turbine specific speed was changed.

Computational fluid dynamic simulations of coal-fired utility boilers: An engineering tool

Fuel ◽  
2009 ◽  
Vol 88 (1) ◽  
pp. 9-18 ◽  
Author(s):  
Efim Korytnyi ◽  
Roman Saveliev ◽  
Miron Perelman ◽  
Boris Chudnovsky ◽  
Ezra Bar-Ziv
Keyword(s):  
Computational Fluid Dynamic ◽  
Fluid Dynamic ◽  
Dynamic Simulations ◽  
Utility Boilers
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