Finned Tubular Air Gap Membrane Distillation

Ethylene-chlorotrifluoroethylene (ECTFE) was first commercialized by DuPont in 1974. Its unique chemical structure gives it high heat resistance, mechanical strength, and corrosion resistance. But also due to these properties, it is difficult to prepare a membrane from it by the nonsolvent-induced phase separation (NIPS) method. However, it can be prepared as a microfiltration membrane using the thermally induced phase separation (TIPS) method at certain temperatures and with the selection of suitable solvents, and the use of green solvents is receiving increasing attention from researchers. The surface wettability of ECTFE membranes usually needs to be modified before use to strengthen its performance to meet the application requirements, usually by graft modification and surface oxidation techniques. This paper provides an overview of the structure of ECTFE and its preparation and modification methods, as well as recent advances in its application areas and prospects for the future methods of preparing high-performance ECTFE membranes.

Section: Ectfe Membrane For Membrane Distillationmentioning

confidence: 99%

Preparation, Modification, and Application of Ethylene-Chlorotrifluoroethylene Copolymer Membranes

Liao,

Wang,

Zhou

et al. 2024

“…∇•(k∇T) = 0 (6) where k is the thermal conductivity and T is the local temperature for the HF membrane, stagnant water gap, or cooling tube metal domains. Additional equations for the feed and membrane diffusion coefficients and thermal conductivity are used in the mathematical model and coupled with the basic conservation equations, and they are listed in Appendix A.…”

Section: Thermal Energy Transport Phenomenamentioning

confidence: 99%

“…MD depends mainly on the partial vapor pressure difference across a hydrophobic membrane, which can be considered as the driving force for the process of vapor molecule diffusion. MD has different configurations depending on the method used to initiate the vapor pressure difference across membrane pores as follows: direct contact MD (DCMD) [1][2][3], in which the hot feed and cold permeate (distillate water) channels are directly in contact with the membrane surfaces that force the vapor molecules to diffuse through the membrane pores and condense in the permeate; air gap MD (AGMD) [4][5][6], in which the permeate channel is replaced by an air gap and the vapor condenses on a cold surface; sweeping gas MD (SGMD) [7][8][9], in which a relatively dry air stream is forced through the permeate channel to carry the diffused vapor molecules to be condensed outside of the desalination unit; 2 of 30 vacuum MD (VMD) [10,11], in which a vacuum pump is applied to the permeate channel to keep a low pressure at the permeate side; and finally, water gap MD (WGMD) [12,13], in which stagnant water is in direct contact with the membrane's cold side, and the stagnant water (water gap) is cooled from the other side using a coolant stream separated by a barrier. In WGMD, the coolant channel is separated from the water gap so that saline water can be used as a coolant to recover a part of the thermal energy that was released in the water gap.…”

Section: Introductionmentioning

confidence: 99%

Productivity and Thermal Performance Enhancements of Hollow Fiber Water Gap Membrane Distillation Modules Using Helical Fiber Configuration: 3D Computational Fluid Dynamics Modeling

Elbessomy,

Elsheniti,

Elsherbiny

et al. 2023

Although hollow fiber water gap membrane distillation (HF-WGMD) units offer certain advantages over other MD desalination systems, they still require enhancements in terms of distillate flux and productivity. Therefore, this work proposes a novel configuration by incorporating the helical turns of HF membranes within the water gap channel of the HF-WGMD modules. A fully coupled 3D CFD model is developed and validated to simulate the multifaceted energy conservations and diffusion mechanisms that are inherent to the transport phenomena in the proposed HF-WGMD module. Single and double helical HF membrane designs with different numbers of turns are compared to the reference modules of single and double straight HF membrane designs under various operational conditions. At a feed temperature of 70 °C, a noteworthy 11.4% enhancement in the distillate flux is observed when employing 20 helical turns, compared to the single straight HF membrane module. Furthermore, the specific productivity revealed a maximum enhancement of 46.2% when using 50 helical turns. The thermal performance of the proposed HF-WGMD module shows higher energy savings of up to 35% in specific thermal energy consumption for a one-stage module. Using three stages of single helical modules can increase the gain output ratio from 0.17 for the single stage to 0.37, which represents an increase of 117.6%. These findings indicate the high potential of the proposed approach in advancing the performance of HF-WGMD systems.

“…Depending on the approach for vapor condensation, MD can be classified into four major configurations [ 13 ], including air gap membrane distillation (AGMD) [ 14 , 15 , 16 , 17 ], sweeping-gas membrane distillation (SGMD) [ 12 , 18 , 19 , 20 , 21 , 22 ], direct contact membrane distillation (DCMD) [ 12 , 23 , 24 , 25 , 26 , 27 ], and vacuum membrane distillation (VMD) [ 12 , 28 , 29 , 30 , 31 , 32 ]. Recently, a new MD configuration that combined the features of AGMD and DCMD processes was introduced and named water gap membrane distillation (WGMD) [ 33 , 34 , 35 ] or permeate gap membrane distillation (PGMD) [ 36 , 37 , 38 , 39 ], or liquid gap membrane distillation (LGMD) [ 40 , 41 , 42 , 43 ].…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of a Plate–Frame Water Gap Membrane Distillation System for Seawater Desalination

Lawal,

Abdulazeez,

Alsalhy

et al. 2023

This study presented a detailed investigation into the performance of a plate–frame water gap membrane distillation (WGMD) system for the desalination of untreated real seawater. One approach to improving the performance of WGMD is through the proper selection of cooling plate material, which plays a vital role in enhancing the gap vapor condensation process. Hence, the influence of different cooling plate materials was examined and discussed. Furthermore, two different hydrophobic micro-porous polymeric membranes of similar mean pore sizes were utilized in the study. The influence of key operating parameters, including the feed water temperature and flow rate, was examined against the system vapor flux and gained output ratio (GOR). In addition, the used membranes were characterized by means of different techniques in terms of surface morphology, liquid entry pressure, water contact angle, pore size distribution, and porosity. Findings revealed that, at all conditions, the PTFE membrane exhibits superior vapor flux and energy efficiency (GOR), with 9.36% to 14.36% higher flux at a 0.6 to 1.2 L/min feed flow rate when compared to the PVDF membrane. The copper plate, which has the highest thermal conductivity, attained the highest vapor flux, while the acrylic plate, which has an extra-low thermal conductivity, recorded the lowest vapor flux. The increasing order of GOR values for different cooling plates is acrylic < HDPE < copper < aluminum < brass < stainless steel. Results also indicated that increasing the feed temperature increases the vapor flux almost exponentially to a maximum flux value of 30.36 kg/m2hr. The system GOR also improves in a decreasing pattern to a maximum value of 0.4049. Moreover, a long-term test showed that the PTFE membrane, which exhibits superior hydrophobicity, registered better salt rejection stability. The use of copper as a cooling plate material for better system performance is recommended, while cooling plate materials with very low thermal conductivities, such as a low thermally conducting polymer, are discouraged.