The Effect of Net-Type Spacer on the Performance of Direct Contact Membrane Distillation System for Seawater Desalination: Heat and Mass Transfer Analysis

2019 ◽  
Author(s):  
Anas M. Alwatban ◽  
Ahmed M. Alshwairekh ◽  
Umar F. Alqsair ◽  
Abdullah A. Alghafis ◽  
Alparslan Oztekin
Keyword(s):  
Reynolds Number ◽  
Direct Contact ◽  
Concentration Polarization ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Membrane Distillation ◽  
Inlet Temperature ◽  
Vapor Permeation ◽  
Direct Contact Membrane Distillation ◽  
Distillation System

Abstract This work aims to study the effects of the net-type spacer on the performance of direct contact membrane distillation (DCMD) modules. Laminar and k-ω SST turbulence models are used to conduct simulations in three-dimensional modules with and without spacers. The spacers are placed in the middle of the feed and permeate channel. The net type spacers of diameter 0.25h and 0.5h were considered, where h is the height of each channel. The inlet temperature of the feed and the permeate channel set to 353 K and 293 K. The feed Reynolds number is varied (500, 1500) while the permeate Reynolds number is fixed at 330. We revealed that the presence of spacer in the flow channels mitigates both the temperature and the concentration polarization and yields higher vapor permeation. We also showed that the module containing larger size spacers yields better flux performance and lower level of temperature and concentration polarization. Moreover, the modules containing spacers become more efficient as the feed flow rate is increased.

Effect of Cell Design on the Thermal Performance of Direct Contact Membrane Distillation System Utilizing a Nanocomposite Membrane

2020 ◽  
Author(s):  
Mohamed R. Elmarghany ◽  
A. H. El-Shazly ◽  
Ali Radwan ◽  
Essam M. Abo-Zahhad ◽  
Norhan Nady ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Energy Consumption ◽  
Pressure Drop ◽  
Specific Energy ◽  
Direct Contact ◽  
Specific Energy Consumption ◽  
Membrane Distillation ◽  
Direct Contact Membrane Distillation ◽  
Distillation System ◽  
Output Ratio

Abstract In the present work, the performance of different cell designs used for the membrane distillation (MD) process was investigated. Three distinctive cell designs were proposed and compared. A numerical simulation using ANSYS Fluent 19 was used to study the performance of the cells. The effects of changing inlet Reynolds number on pressure drop, salt concentration and velocity contours with in the different cell deigns were investigated. Results show that the pressure drop is minimum across the first design, and the salt concentration decreases as Reynolds number increases. At Reynolds number = 125, the results show an enhanced velocity distribution compared to Reynolds number = 250 and 50. One of the proposed cell designs was then fabricated to study the effect of fluid flow on the performance in a direct contact membrane distillation system. Energy parameters were calculated to evaluate the performance of the cell. An evacuated tube solar collector was used to provide the system with hot water. System thermal efficiency, gained output ratio, and specific energy consumption analysis were performed for the system. The increase in the feed flow rate almost doubled the system thermal efficiency and the gained output ratio was increased from 0.31 to 0.60, while the specific energy consumption decreased from 2064 to 1037 kWh/m3.

Comparison of Sweeping Gas and Direct Contact Membrane Distillation: Module Length Effect

2020 ◽  
Author(s):  
Umar F. Alqsair ◽  
Ahmed M. Alshwairekh ◽  
Anas M. Alwatban ◽  
Robert Krysko ◽  
Alparslan Oztekin
Keyword(s):  
Direct Contact ◽  
Three Dimensional ◽  
Concentration Field ◽  
Local Variation ◽  
Membrane Distillation ◽  
Membrane Properties ◽  
Effect Of Temperature ◽  
Vapor Flux ◽  
Direct Contact Membrane Distillation ◽  
Sweeping Gas

Abstract Computational fluid dynamics simulations are conducted to compare the effect of module length in sweeping gas and direct contact membrane distillation systems for seawater desalination processes. In this work, the effect of temperature and concentration on the flux performance and temperature and concentration polarization characteristics are studied. CFD simulations are conducted in a three-dimensional module to characterize the steady-state velocity, temperature, and concentration field in the feed and permeate channel. The Reynolds number for the feed and the permeate stream is set to 500 and 1500, and thus the laminar flow model is adapted for each channel. The membrane properties are fixed in all cases considered. It is revealed that the local variation of the vapor flux, TPC, and CPC varies with module length in SGMD systems. However, the average values along the membrane in both module lengths do not vary much. Remedies for mitigating temperature polarization should be considered for future studies.

Development of a novel submerged tubular direct-contact membrane distillation system for saltwater treatment

2020 ◽  
Vol 200 ◽  
pp. 55-64
Author(s):  
Thi-Tra-My Ngo ◽  
Xuan-Thanh Bui ◽  
Kim-Triet Dang ◽  
Thanh-Tin Nguyen ◽  
Shiao-Shing Chen ◽  
...  
Keyword(s):  
Direct Contact ◽  
Membrane Distillation ◽  
Direct Contact Membrane Distillation ◽  
Distillation System

scholarly journals Numerical Simulation of Low Energy Direct Contact Membrane Distillation

2014 ◽  
Vol 07 (2) ◽  
Keyword(s):  
Direct Contact ◽  
Membrane Distillation ◽  
Low Energy ◽  
Model Parameters ◽  
Inlet Temperature ◽  
Vapor Flow ◽  
Two Dimensional ◽  
Counter Flow ◽  
Permeable Membrane ◽  
Direct Contact Membrane Distillation

Computational Fluid Dynamics (CFD) is used to study the steady state performance of Low Energy Direct Contact Membrane Distillation (DCMD). Two-dimensional numerical model with parallel and counter flow is developed. A case of fully developed pressure driven parabolic flow is considered entering the domain at the feed and the permeate sides at 40 C and 25 C, respectively. The model parameters were measured in the consideration of two dimensional fluid flow governed by the complete Navier-Stokes coupled with the energy equation for non-isothermal laminar flow. The feed stream is water at water 4% salinity, whereas the permeate stream is comprised of pure water. Across the membrane the temperature difference creates a pressure gradient responsible for the transport of vapor mass through the pours of the permeable membrane. The vapor flow is driven by two mechanisms, Knudson and Poiseuille flow. The membrane’s coefficients of DCMD membrane is evaluated along with the mass flux, heat flux, and temperature polarization factor and results showed a good agreement with the published theoretical work. In view of these plausible results, parametrical study is carried out accounting for parallel and counter flow, different flow rates and inlet temperature in an attempt to achieve optimal or better yield to the Multi stage flashing method.

scholarly journals Thermal analysis evaluation of direct contact membrane distillation system

2019 ◽  
Vol 13 ◽  
pp. 100377 ◽  
Author(s):  
Mohamed R. Elmarghany ◽  
Ahmed H. El-Shazly ◽  
Mohamed S. Salem ◽  
Mohamed Nabil Sabry ◽  
Norhan Nady
Keyword(s):  
Thermal Analysis ◽  
Direct Contact ◽  
Membrane Distillation ◽  
Direct Contact Membrane Distillation ◽  
Distillation System
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