Feed Channel Research Articles

Effect of feed spacer geometric design in a spiral wound module of reverse osmosis process on the removal of dimethyl phenol from wastewater. Simulation‐based model

AbstractThe reverse osmosis (RO) technology has engaged in the removal of a wide set of pollutants including dimethylphenol at a high rejection. The goal of this research is to explore the influence of spacer geometric design on the performance metrics of an individual spiral wound module of RO process to eliminate dimethylphenol from wastewater. The study entails the embedding of an author's model developed to envisage the performance of a spiral wound membrane‐based wastewater treatment with a detailed model of feed spacer (collected from the open literature) utilised to characterise the pressure drop along the feed channel. A comprehensive simulation study is conducted to observe the impact of feed flow rate on the energy dissipation and mass transfer coefficient of several selected feed spacers of different design characteristics. Accordingly, the consequence of feed spacer design parameters was analysed on the performance metrics of RO process including the dimethylphenol rejection and water recovery. It is found that the angle of flow diversion, voidage, and feed spacer height have a considerable effect on the pressure drop, mass transfer coefficient, and axial velocity, which accordingly affect the overall performance indicators. The results show the success of feed spacers 80MIL‐1 and 80MIL‐2 to gain the highest dimethylphenol rejection and associated water recovery.

A reduced-order model of concentration polarization in reverse osmosis systems with feed spacers

Feed spacers in reverse osmosis systems generate complex fluid flows that limit computational fluid dynamics (CFD) simulations to small length and time scales. That limits our ability to simulate mineral scaling and other membrane fouling phenomena, which occur over longer length and time scales. Thus motivated, we develop a reduced model that replaces the CFD simulation of the velocity field with an analytical model that mimics spacers. This focuses the remaining numerical effort on simulating the advection–diffusion equation governing solute transport. We motivate and validate the model with CFD simulations and bench-scale experiments of spacer filaments in three different arrangements, including cases of unsteady vortex shedding. We show that the model produces a roughly 10,000-fold speedup compared to CFD, and accurately reproduces CFD predictions of not only the average and maximum concentrations, but also the local concentration distribution along the membrane. We also demonstrate the model for simulating a feed channel with a length-to-height ratio of 200. The model provides a simple testbed for exploratory studies of multispecies transport, precipitation, and membrane fouling phenomena for which simulating spacers is often prohibitive.

Multilayered membrane spacer: does it enhance solution mixing?

AbstractThe present review systematically investigates and illustrates the effect of multilayered membrane spacers on the features of fluid dynamics that influence all performance metrics. Multilayer spacers are frequently composed of three sets of filaments (i.e., top, middle, and bottom layers), which has the benefit of increasing mass transfer and decreasing membrane surface fouling when compared to ordinary monolayer (e.g., extruded spacer) and two‐layer spacers. The review found that the multilayer spacer's middle layer disperses primary flow to the thin side spacers placed near the membrane's surfaces. The thin side spacers will then form narrow passageways to keep the solution in situ for as long as mass transfer is achievable. The employment of thin spacers close to the membranes at satisfactory operational conditions (e.g., adequate flow velocity) results in swirling flows and incorporation of transverse and longitudinal eddies near to the membranes, reducing the boundary layer's width and making the associated ion concentration domain at the membranes much more consistent. The concept and implementation of multilayer geometry in feed channels appears to be promising, since a multilayered spacer can function at a lower maximum flow velocity than normal two‐layer spacers, saving operational energy while minimizing concentration gradients at the membrane surfaces. Furthermore, the multilayer structure's durability and mechanical strength may help to reduce membrane deformation and maintain long processes. Future studies might look at significantly reducing spacer thickness for industrial uses. © 2023 Society of Chemical Industry (SCI).

Experimental study of a standalone membrane water desalination unit fully powered by solar energy

In this study, a fully solar-driven water desalination system is designed, fabricated, and tested. The proposed system is designed for remote, isolated areas with limited electricity and freshwater access. For commercial PVDF membranes, the performance of the MD unit is evaluated at various feed temperatures, flow rates, and salt concentrations. In addition, the effect of MD cell design was examined to determine the effect of the obstacles on the feed channel. Increasing the temperature by 20 degrees from 55 to 75 °C enhances productivity by 165 % from 6.2 to 16.4 kg/m2.h. At different operating conditions, the new design of the MD cell with cylindrical obstacles attained higher flux productivity compared to the conventional MD cell design. The maximum attained freshwater output flux was around 15 kg/m2.h at a feed inlet temperature of 65 °C and feed mass flowrate of 66 kg/h for the MD cell with cylindrical obstacles. In the presence of obstacles, a reduction in the specific energy consumption (SEC) by 35–15 % is associated with an increase in the gain output ratio (GOR) by 50–20 % compared to the case of no obstacles. Observations indicate that a small PV module with an area of 0.377 m2 is sufficient to operate the membrane unit for contentious 15 h. Collectively, using solar MD units collectively has the potential to be used for decentralized desalination of water.

MRI on a new polymeric multichannel membrane for ultrafiltration

Membrane ultrafiltration in new polymeric multi-channel membranes designed for in-out filtration was investigated to get insights into structure, flow and filtration properties. The apparent novelty of the membrane concerns the geometry and configuration of the feed channels.In-situmagnetic resonance imaging (MRI) allows non-invasive and non-destructive investigations with adequate spatial and time resolution. The structure of the new polymeric membrane was measured with an in-plane spatial resolution of 35 µm/pixel revealing first the polymer density distribution over the 19-channel membrane and second the wettability of the fiber and its cavities of different dimensions. MRI was also used to answer questions about flow and consequently feed distribution in the channels. Finally,in-situfiltration of an aqueous solution of sodium alginate was observed which led to deposit formation at the channel’s inner surfaces. The kinetics of this deposit formation was quantified. Backwashing and flushing gave insight into the cleanability of the channels.

Electrodialysis desalination: The impact of solution flowrate (or Reynolds number) on fluid dynamics throughout membrane spacers

The incorporation of a spacer among membranes has a major influence on fluid dynamics and performance metrics. Spacers create feed channels and operate as turbulence promoters to increase mixing and reduce concentration/temperature polarization effects. However, spacer geometry remains unoptimized, and studies continue to investigate a wide range of commercial and custom-made spacer designs. The in-depth discussion of the present systematic review seeks to discover the influence of Reynolds number or solution flowrate on flow hydrodynamics throughout a spacer-filled channel. A fast-flowing solution sweeping one membrane's surface first, then the neighboring membrane's surface produces good mixing action, which does not happen commonly at laminar solution flowrates. A sufficient flowrate can suppress the polarization layer, which may normally require the utilization of a simple feed channel rather than complex spacer configurations. When a recirculation eddy occurs, it disrupts the continuous flow and effectively curves the linear fluid courses. The higher the flowrate, the better the membrane performance, the higher the critical flux (or recovery rate), and the lower the inherent limitations of spacer design, spacer shadow effect, poor channel hydrodynamics, and high concentration polarization. In fact, critical flow achieves an acceptable balance between improving flow dynamics and reducing the related trade-offs, such as pressure losses and the occurrence of concentration polarization throughout the cell. If the necessary technical flowrate is not used, the real concentration potential for transport is relatively limited at low velocities than would be predicted based on bulk concentrations. Electrodialysis stack therefore may suffer from the dissociation of water molecules. Next studies should consider that applying a higher flowrate results in greater process efficiency, increased mass transfer potential at the membrane interface, and reduced stack thermal and electrical resistance, where pressure drop should always be indicated as a consequence of the spacer and circumstances used, rather than a problem.

Dynamic evolution of membrane biofouling in feed channels affected by spacer–membrane clearance and the induced hydrodynamic conditions

Membrane biofouling is regarded as a Gordian knot in applying reverse osmosis and nanofiltration for water treatment. It occurs in the feed spacer channels of spiral wound membrane elements. The influence of feed spacer structure on hydrodynamic condition and biofouling development remains yet to be fully understood. This study aims to quantify the dynamic evolution and spatial distribution of biomass in feed spacer channels, and reveal the great importance of spacer–membrane clearance in the biofouling development. Four kinds of feed spacers with the same thickness (28 mil) but different clearance width, by varying filament diameter (0.4, 0.45, 0.55 and 0.6 mm), were used. A relatively long-term (20 d) biofouling experiment was conducted by using a feed solution of lower bacterial load and nutrient dosage. Results showed that the “shear stress effect” dominated the early stage of biofouling as biofilm was first attached to the low-shear regions, regardless of the spacer–membrane clearance width. In the middle and late stage, the “blocking effect” emerged with the continuous accumulation of biomass, as was especially the case in the feed channel with narrow spacer–membrane clearance. In this period, biofilm was prone to deposit and block the narrow flow passage between the spacer filaments and membrane surface, which decreased the uniformity of flow field, expanded the flow “dead zone” area, boosted the feed channel pressure (FCP) drop, and resultantly accelerated the rate of membrane biofouling. Enhancement of the “shear stress effect” under an appropriate range of spacer–membrane clearance width and thus channel porosity, as well as customed design of feed spacer geometries according to specific fouling locations are suggested for the future optimization of feed spacer.

Numerical simulations of membrane distillation systems with actively heated membranes

Membrane distillation (MD) is a thermal desalination process that is gaining attention for treating hypersaline brines. One recent approach uses composite membranes with a thermally conductive layer that delivers heat to the membrane–feed interface, where it drives evaporation. Though this increases single-pass recovery, it comes with the challenge of promoting lateral heat conduction through the thin membrane. Herein, we develop a 3D, computational fluid dynamics (CFD) model that simulates conjugate heat, mass, and momentum transport in the feed channel and composite membrane. We then use the CFD to verify a simpler numerical model that approximates the feed velocity field analytically. We validate the numerical model experimentally, and use it to investigate the impacts of the conductive layer thickness, feed channel geometry, and operating conditions on temperature and concentration polarization, permeate production, and specific energy consumption. Overall, we find that lateral heating increases permeate production at the expense of increased concentration polarization. In extreme cases, the concentration increases more than four-fold along the membrane surface. We show however, that the feed flow rate and conductive layer thickness can be tailored to mitigate concentration polarization, for only a small reduction in permeate production.

Performance Evaluation of Tillage Knife Discharge Microchannel

Abstract Liquid mineral fertilizers (LMF) have a high sorption ability, can be metered precisely, and the intra-soil application of LMF is relevant. However, the agricultural equipment for this process that introduces the liquid fertilizer under processed soil layer in the form of a wide band has not yet been proposed. The purpose of the study is to evaluate the performance of a 102 mm wide rectangular discharge microchannel of the proposed soil tillage knife designed for deep tillage and intra-soil application of liquid fertilizers and to study the influence of the microchannel length (L) and slot height (h) on the uniformity of discharge. Solidworks Flow Simulation® was used during investigations, and simulation results were compared with experiment results. It has been determined that the effective slot height for water discharge at V i = 3–4 m·s−1 is 0.1 (±0.01) mm, an effective microchannel length is 20 (±2) mm, and the influence of L depends on h. Sheet thickness will not change at a distance of 10–15 mm (b). Fall angle is 0–5°. In conclusion, the proposed discharge microchannel with asymmetrical feed is applicable for intra-soil application of LMF, and the surface tension effect has to be considered. A way to enhancing the sheet uniformity is the geometrical modification of feed channel shape.

CFD simulation and optimization of an energy-efficient direct contact membrane distillation (DCMD) desalination system

In this paper, the CFD simulation and optimization of an energy-efficient direct contact membrane distillation (DCMD) desalination system in a counter-current flow mode are performed. Two-dimensional modeling was applied and the governing equations for momentum, heat, and mass transfer in the three regions i.e., feed channel, membrane, and permeate channel were solved and corresponding velocity, temperature, concentration fields, and the permeate water flux through the membrane was obtained. A two-step approach was considered to optimize the desalination system through the MD process. First, the model results were validated with the reported experimental data and good agreements were observed. The maximum deviation for the outlet concentration and hot stream outlet temperature with different feed velocities and temperatures was 0.33%. Then, the process was optimized for maximizing the permeate flux. Since the number of parameters was high, the response surface methodology (RSM) was used to find the optimum condition in order to obtain the maximum water flux. It was determined that the highest permeate water flux would be gained at the permeate temperature, the hot feed flow rate, the cold-water flow rate, the length and height of the channels of 35 °C, 20 lit/min, 10.25 lit/min, 20 cm, and 3 cm, respectively. At this optimum condition, a permeate flux of 53.5 kg/m2.h and a TPC of 0.82 are expected.

Enhance the anti-scaling performance of conductive heating vacuum membrane distillation by carbon nanotube-based electroactive membrane

Membrane distillation (MD) is an emerging technology for the brine desalination. Directly heating feed liquid at the membrane-water interface for improving the performance of MD has been demonstrated, while the problem of membrane scaling remained. Herein, carbon nanotube-based electroactive membranes were prepared and characterized by a variety of methods. It was then used in a conductive heating vacuum membrane distillation system. We firstly increased the flux by optimizing system configuration, placing a spacer in the feed channel, and setting vent holes on the thermal conducting layer. Then, aiming at silicates and sulfates scaling in MD, the electroactive membranes and titanium were used as working electrodes and the counter electrode, respectively, to discuss the electrochemical anti-scaling performance and mechanism. Results showed that the silicate scale on the membrane surface can be effectively cleaned by using the electroactive membrane as the cathode and applying a potential of − 5 V to destroy the structure of the silicate through an electrochemical reaction. With the electroactive membrane as the anode, the scaling of calcium sulfate can be mitigated by providing a continuous potential through electrostatic repulsion. This paper may provide further insights into inorganic scaling control in conductive heating vacuum membrane distillation process.

Challenges Facing Pressure Retarded Osmosis Commercialization: A Short Review

Pressure-retarded osmosis (PRO) is a promising technology that harvests salinity gradient energy. Even though PRO has great power-generating potential, its commercialization is currently facing many challenges. In this regard, this review highlights the discrepancies between the reported power density obtained by lab-scale PRO systems, as well as numerical investigations, and the significantly low power density values obtained by PRO pilot plants. This difference in performance is mainly due to the effect of a pressure drop and the draw pressure effect on the feed channel hydrodynamics, which have significant impacts on large-scale modules; however, it has a minor or no effect on small-scale ones. Therefore, this review outlines the underlying causes of the high power density values obtained by lab-scale PRO systems and numerical studies. Moreover, other challenges impeding PRO commercialization are discussed, including the effect of concentration polarization, the solution temperature, the pressure drop, and the draw pressure effect on the feed channel hydrodynamics. In conclusion, this review sheds valuable insights on the issues facing PRO commercialization and suggests recommendations that can facilitate the successful development of PRO power plants.

Hybrid mechanistic approach in the estimation of flow properties in cylindrical membrane modules

A hybrid computational approach was employed for simulation of molecular separation using polymeric membranes. The considered system is a cylindrical membrane module in which the mass transfer equations were solved numerically using CFD (Computational Fluid Dynamics) to obtain the concentration of the species, and then the simulation results were used in machine learning models. Indeed, the CFD simulation results were used as the inputs for several machine learning models to obtain the hybrid model. We have a dataset with more than 2000 data points and two input features (r and z). Also, the only output is C which is the concentration of the species in the feed channel of membrane module. KNN (K nearest neighbor), PLSR (Partial Least Square Regression), and SGD (Stochastic Gradient Descent) are the models employed in this research to analyze the mentioned data set. Models were optimized with their hyper-parameters and finally evaluated with different statistical metrics. MAE error metric is 3.4, 5.1, and 5.5 for KNN, SGD, and PLSR. Also, they have 0.998, 0.997, 0.896 coefficient of determination (R2) respectively. Finally, based on the overall results, KNN with K = 8 is selected as the best model in this study for simulation of the membrane system. The final maximum error is also 1.35E+02.

Design, failure analysis, and optimization of a high-flow water valve: A case study

An 800-L/min high-flow water cartridge poppet valve with the commonly used single feed channel was designed to meet the moving speed of the hydraulic powered roof support in the coal mine. Mathematical model was used to explore the dynamic displacement of the valve, and the experimental displacement was measured to verify the accuracy of the simulation value. However, an interesting phenomenon occurred that the experimental opening and closing time of the valve becomes longer and longer with the increase of flow, even vibration appears when the flow is up to 800 L/min, and the simulation error is also getting bigger. To find the reason and solutions, the computational fluid dynamics technology is used. It is discovered that the valve is subjected to radial imbalanced force that is not considered in the initial mathematical model, which leads to big simulation error at high flow condition. Then, the new mathematical model is proposed. The relative simulation error of the response time decreases to 11.7% from 33.3% in the opening process and decreases to 4.6% from 76.9% in the closing process at 800 L/min. A symmetrical dual channel is designed to improve the performance of the valve. The imbalanced force on the dual-channel valve is 63.9% lower than that of the original valve, and the corresponding opening and closing time decreases by 37.5% and 69%, respectively. Furthermore, a double channel valve with auxiliary passage is proposed for super high flow valves. The innovation of this study is correcting the mathematical model by considering the additional radial imbalanced force induced by the asymmetrical flow channel of the valve. It is of great help to successful design of the 800-L/min water directional valve. The case study systematically provides reference for design, failure analysis, and optimization of new products in fluid engineering.

Numerical simulations of the effect of spacer filament geometry and orientation on the performance of the reverse osmosis process

Momentum and mass transfer in reverse osmosis membrane modules must be optimized to design efficient and economical designs. The feed spacers are used to improve mixing, to minimize fouling and concentration polarization. This computational study analyses fluid flow, mass transfer, concentration polarization and pressure drop in the feed channel of a reverse osmosis membrane module with different spacer filament geometry (cylindrical, diamond, pentagonal, and triangular), orientation and Reynolds numbers. The computational model solves three-dimensional fluid flow and mass transfer while considering the complex water and solute flux boundary conditions. The cylindrical spacer filaments configurations showed the lowest water flux, followed by pentagonal, diamond, and triangular spacer filaments configurations. The concentration boundary layer thickness was high near the spacer surface due to the stagnant velocity zone. The results indicated that the concentration polarization on the membrane surface increases with a decrease in Reynolds numbers. The channel containing triangular filament spacers gave the maximum water flux and minimum concentration polarization. The spacer configurations with an attack angle of 45° and a transverse angle of 135° showed the highest water flux; however, the pressure drop was also high. The channel containing triangular spacer filament (T1A0) showed the least CP. However, the concentration boundary layer thickness was higher at the bottom side of the channel. The developed model could be useful for predicting the reverse osmosis membrane process performance.

Research and Comparative Testing of a Grain Flattener with a Feeding Device

Introduction. The article presents the results of experimental and theoretical research of technological process of the PZ-1M grain flattener with a feeding device. The research was carried out at the Federal Agricultural Research Center of the North-East Named after N. V. Rudnitsky in 2011‒2019. The purpose of the research is to design a feeder scheme for the grain flattener, determine rational parameters of its working body (feed roller) and test the improved grain flattener. Materials and Methods. A constructive and technological scheme of the grain flattener with a feeding device is proposed, the novelty of which is confirmed by patents Nos. 2628297 and 2557780. The structural scheme of grain flattener with a feeding device comprising an active working body – a feeding roller with blades is developed. There was carried out theoretical research of the grain motion along the feeder roller blades to determine the patterns of grain motion depending on the values of the roller parameters. Results. It is established that with the size of the feed roller inner radius 0.045 m and more all the grain passes down from the roller blade into the feed channel and through it for flattening at the required exit angle of 60°, roller speed of not less than 400 min–1 and the value of the coefficient of the grain friction on the roller blade less than 0.4. When these parameters are observed, the feeding roller and the device are effective. Taking into account the results of researches, we have developed the design documentation and produced the PZ-1M grain flattener comprising a feeder. Departmental and comparative tests of the flattener were conducted, which showed high efficiency of its application: machine reliably and qualitatively performs the technological process of flattening grains. Discussion and Conclusion. The use of a power device in the design of the flattener increases the conditioning capacity by 2.08 times while reducing the energy intensity of the process by 1.6 times; the annual economic effect of using the PZ-1M grain flattener with feeding device compared to its analogue is 67,583 rub. at the level of intensification of 49%.

FORMULA FOR THE DURABILITY OF OIL AND GAS FIELDS

The article is concerned with the issues of the status and results of long-term development of oil and gas fields, with consideration and justification of the factors that influence the extension of their further cost-effective development. To evaluate the potential factors of “plant life extension” of hydrocarbon reservoirs, the Munaily field in above-salt deposits of the southeastern part of the PreCaspian Depression has been designated as a pilot option. Pursuant thereto, the sequence of the major stages in the study and development, as well as the specific features of this field are provided. The forecast made by the authors for the longevity of field production is based on the factor of natural replenishment of reserves, which can be achieved through the establishment of certain restrictive measures and observance of the optimum operation mode appropriate for the conditions of each particular field. This refers to the setting of optimal oil withdrawals, the average daily flow rate of the well, etc. Determination of this pattern and its use in practical terms has favorable historical prerequisites, which is confirmed by the example of numerous objects under development in Russia and Kazakhstan. When substantiating this forecast, the main features of the geological structure of the Munaily field have also been taken into account, among which considerable importance in evaluating the mode of occurrence and productivity of above-salt deposits in the Pre-Caspian Depression is given to the presence and impact of underlying complexes of sediments. This concerns the salt-bearing section of the Kungurian age, the subsalt Paleozoic strata, and the influence of fault tectonics, which contributes to the development in the field section of certain oil and gas feed channels due to disturbances of various order, zones of decompaction, and fracture porosity of the rock formations. Following the results of the analysis, the necessity of compliance with the rehabilitation cycle of 10-15 years has been substantiated, which allows restoring the internal indicators of the energy state and the volume of hydrocarbons in line with the existing model of the reservoir (trap) of the field to the level at which the continuation of further cost-effective development is possible.

CFD simulations of flow fields during ultrafiltration: Effects of hydrodynamic strain rates with and without a particle cake layer on the permeation of mobile genetic elements

Membrane ultrafiltration (UF) combined with inline dosing of powdered activated carbon (PAC) are popular hybrid processes for water reclamation. However, hydrodynamic forces can allow mobile genetic elements (MGEs) that are larger than the membrane pore size to penetrate through UF membranes. The flow fields in the feed channel of a dead-end UF membrane module were modelled using computational fluid dynamics (CFD) in order to analyze shear and elongational strain rates and associated potential hydrodynamic effects by a PAC particle layer on MGE retention. The most significant magnitudes of strain rates occurred within a distance of tens of nanometers from the membrane surface, meaning that this is where significant deformation of MGEs occurs. Since flow fields were not considerably altered at the membrane surface, the presence of the PAC particle layer was expected to have a negligible impact on the permeation of MGEs through UF membrane pores.

The critical role of feed spacer channel porosity in membrane biofouling: Insights and implications

Membrane biofouling is a major hindrance limiting the efficiency of spiral wound membrane (SWM) module for water treatment. Feed spacer is an imperative component of SWM module which creates feed channels, determines fluid field and thus influences biofilm development via its geometry. Yet, the role of feed spacer channel porosity in biofilm development remains unclear. In this study, 16 feed spacers of varied geometric parameters and thus different channel porosities were used for both numerical simulations and biofouling experiments. Results showed that the hydraulic and anti-biofouling performances were more sensitive to the variation of filament diameter and spacer thickness. Feed channel porosity as a gross parameter played a pivotal role in biofouling development. The high-porosity (> 0.85) feed spacer channels exhibited a slower increase of feed channel pressure drop when biofouling occurred, but with more biomass accumulated in the middle of spacer meshes because of lower shear stress. For the low-porosity (< 0.75) channels, biofilm incipiently developed from the interspace region between spacer filaments and membrane surface due to “block effect”, which aggravated “narrow channeling” and induced a larger area of dead zone, leading to more severe biofouling ultimately. An appropriate channel porosity was suggested at ∼0.85 based on the hydraulic and anti-biofouling performances conjointly in this study.

In situ conductive spacers for early pore wetting detection in membrane distillation

Membrane distillation (MD) suffers from pore wetting which deteriorates membrane separation properties and causes water protrusion to permeate side. The early detection of pore wetting is a challenge which needs to be addressed to achieve stable MD performance. In this study, electrically-conductive Pt-coated spacers placed inside the feed and coolant channels with a dual purpose of maximizing permeate flux and instantaneous wetting detection once first membrane pores are compromised are proposed. Upon wetting, permeate salt concentration increases thereby initiating redox reactions at two spacer electrodes under the applied electrical potential. As a result, electrical current is produced and measured. The competence of the proposed wetting detection method was explored in MD process in the presence of organic substances with high wetting propensity. An increase in generated electrical current upon wetting development and substantial signal amplification with the voltage increase was demonstrated. The new wetting detection method achieved a faster response comparing to conventional conductivity measurements. Moreover, this method allows to define the wetting onset which can serve as an indication of early membrane impairment. Different spacer geometries and observed no adverse effect of spacer coating on MD performance were further compared. Experimental and numerical simulations accentuated an importance of spacer design by providing specific permeate flux gain for a 1-helical spacer comparing to a spacer with a smooth cylindrical filament. This effect became more evident at higher feed water temperature, condition that favors greater temperature polarization.