Increment Of Flux Research Articles

Effect of twisted tapes and surface extensions in enhancing the condensation heat transfer of high-temperature saturated steam in a circumferential rectangular channel

This article numerically investigates the impact of twisted tapes and extended surfaces (fins) on enhancing high-temperature steam flow in a circumferential rectangular channel, akin to the external jacket cavity of a tyre cure press. The passive enhancement techniques for improving the mold warm-up time of the tyre curing process have received limited attention in previous studies, which have primarily focused on enhancing heat transfer in configurations and working conditions typical of heat exchanger applications. The objective of this article is to enhance the condensation heat and mass transfer rate by geometrically modifying the internal flow path of the circumferential rectangular channel, resembling an external jacket cavity of a tyre cure press, using twisted tapes and extended surfaces. Four configurations are simulated: i) conventional circumferential rectangular channel, ii) channel with twisted tapes, iii) channel with surface extension, and iv) channel with both twisted tapes and surface extension. The heat transfer performance of all the modified channel configurations derived from the simulation results is assessed in comparison to the conventional channel. The channel, featuring a design that includes five twisted tapes with a twist ratio of 8 and 54 extended surfaces, records a substantial 36.85% rise in heat flux along with a notable 24% increment in the condensation mass flux. The simulation results are validated using an in-house experimental study. The tyre cure press in the experimental setup is modified to align with the design proposed by the simulation results, and a warm-up study is conducted. The warm-up time for the modified mold to attain the desired temperature is reduced by 33%, with no accompanying increase in steam consumption, compared to the warm-up time for the conventional mold. This significant reduction in mold warm-up time holds immense potential in enhancing the productivity rate, an ongoing requirement of the automobile industry.

Internal flow characteristics of radial rotating oscillating heat pipe filled with acetone or water

The study investigates the internal flow dynamics of radial rotating oscillating heat pipes (RaRo-OHPs) to assess their potential applications in rotations. It examines influences of heat flux and centrifugal acceleration on thermal conditions and internal flow in RaRo-OHPs. Results show that both Bo and Fr rise significantly with increased centrifugal acceleration and heat flux, emphasizing radial rotation's impact on internal flow. With increment of heat flux and centrifugal acceleration, flow pattern analysis reveals shifts from slug/annular flow to churn flow/separation of vapor-liquid phases; motion modes progress from pendulum oscillation to circulation, then oscillation or single/double-side boiling. Visualizations underscore the importance of maintaining vapor slugs and liquid plugs for effective circulation flow and heat transfer. It is noted that under radial rotation, slug flow and the circulation of chains of vapor slugs and liquid plugs were still observed, achieving Bo of 8.26 for acetone and 5.10 for water as the working fluid. Compared with the static state, radial rotation can promote the internal flow, the velocity increases by 228% and 185% for RaRo-OHPs filled with acetone and water, respectively. The study emphasizes the capillary effect's role in enhancing internal flow under radial rotations, crucial for improving thermal performance.

Seasonal variations of organophosphate esters (OPEs) in atmospheric deposition, and their contribution to soil loading

Organophosphate esters (OPEs) are ubiquitous in surface soil, and atmospheric deposition is considered to be the major pollution source. However, the research on the environmental transport behaviors of OPEs between atmospheric deposition and soil is very limited. In this study, we investigated the contamination levels and seasonal variations of OPEs in atmospheric deposition samples (n = 33) collected from an area of South China every month between February 2021 and January 2022, and evaluated the contribution of OPEs in atmospheric deposition to soil. The concentrations of ∑21target-OPEs ranged from 3670 to 18,600 ng/g dry weight (dw), with a mean of 8200 ng/g dw (median: 7600 ng/g dw). ∑21target-OPEs concentrations in all atmospheric deposition samples exhibited significant seasonal differences (p < 0.05) with higher concentrations observed in winter and lower concentrations in summer. Tris(2,4-di-tert-butylphenyl) phosphate (TDTBPP) was the most dominant target OPE in atmospheric deposition (4870 ng/g dw), and its seasonal variation trend was consistent with ∑21OPEs (p < 0.05). Simultaneously, in order to further explore the effect of atmospheric deposition on the levels of OPEs in soil of the study region, input fluxes and accumulation increments were estimated. Ten OPEs (including seven target OPEs and three suspect OPEs) exhibited high input flux means and accumulation increments, indicating that these compounds are prone to accumulate in soil via atmospheric deposition. It is noteworthy that the non-target phosphonate analyte bis(2,4-di-tert-butylphenyl) dibutyl ethane-1,2-diylbis(phosphonate) (BDTBPDEDBP) was detected at highest median concentration (8960 ng/g dw) in atmospheric deposition. Correspondingly, the average input flux and accumulation increment of BDTBPDEDBP were higher than those of all target and suspect OPEs. Collectively, this study quantifies the environmental transport behavior of OPEs between atmospheric deposition and soil, and provides new evidences for the fact that atmospheric deposition is the important pollution source of OPEs in soil.

Numerical Simulation of the Influencing Factors of Array Jet Shock Cooling

Array jet impingement cooling is a significant technology of enhanced heat dissipation which is fit for high heat flux flow with large area. It is gradually applied to the cooling of electronic devices. However, The researches on the nozzle array mode and the uniformity of cooling surface still have deficiencies. Therefore, the influence of heat flux, inlet temperature, jet height, array mode and diversion structure on jet impingement cooling performance and temperature distribution uniformity is analyzed by means of numerical calculation. The results show that the heat transfer coefficient of jet impingement cooling increases linearly with the increment of heat flux and inlet temperature. With the increment of the ratio of jet height to nozzle diameter (H/d), the heat transfer coefficient increases first and then decreases, that is, there is an optimal H/d, which makes the heat transfer performance of the array jet impact cooling best. The temperature uniformity of array jet impact cooling is greatly affected by array mode. The improvement effect of nozzle array mode on temperature uniformity is ranked as sequential &amp;gt; staggered &amp;gt; shield &amp;gt; elliptical array. The overall temperature uniformity and heat transfer coefficient are increased by 5.88% and 7.29% compared with elliptical array. The heat transfer performance can be further improved by adding a flow channel to the in-line array layout, in which the heat transfer coefficient is increased by 6.53% and the overall temperature uniformity is increased by 1.45%.

A computational fluid dynamics study on TPMS-based spacers in direct contact membrane distillation modules

Feed spacers are incorporated in membrane modules to enhance fluid mixing, thereby enhancing membrane flux. Previous experimental work showed that triply periodic minimal surfaces (TPMS)-based spacers induce significant improvements in membrane distillation (MD) performance, which was attributed to the suppression of membrane boundary layer, reducing heat and mass transfer resistance. To corroborate those findings, in this study, we assess the performance of TPMS spacers in direct contact MD (DCMD) modules using computational fluid dynamics (CFD). Results showed that the Fischer-Koch S TPMS spacer topology achieved twice the flux of the empty channel case and exhibited a 13 % increment in flux compared to the net-type spacer, but this improvement was accompanied by a higher pressure drop in the feed channel. Therefore, a normalized power ratio (NPR) was used to evaluate the overall performance of spacers. For Reynold number (Re) ranging between 200 and 1200, Fischer-Koch S spacer had a 12 % improvement in NPR compared to the net-type spacer and resulted in higher shear stress near the membrane surface, indicating a promising mean for mitigating fouling in membrane distillation. This research highlights the importance of utilizing novel spacers in membrane distillation and showcases the power of CFD tools in optimizing the process.

Hydrodynamic effects of the elliptical spacer filament on the flow and mass transfer in a desalination membrane channel

This study numerically investigates the impacts of an elliptical spacer on the flow and mass transfer within a desalination membrane channel. We consider the effects of the fluid Reynolds number, the elliptical spacer position yin/H, the flow attack angle θ and the aspect ratio B of spacer on the fluid flow, concentration polarization, and permeation flux. Our findings reveal that the elliptical spacers can improve both the mass transfer and permeation flux compared with the traditional circular spacers. Placing the spacer near the membrane surface effectively disrupts the concentration boundary layer, thereby amplifying the local concentration polarization surrounding the spacer. A single recirculation vortex behind the spacer induces numerous large vortices around the membrane, resulting in a significant increment in freshwater production. By changing θ and B, the system's stability can be reduced, potentially leading to a 16.0% increment in permeation flux when compared with the traditional circular spacers. Furthermore, the drag and lift coefficients acting on the elliptical spacer are greater than those of circular spacers, which is the main reason for the transition of flow condition. Our findings provide a reference for the design of the efficient structures in reverse osmosis membranes.

Comparison of Statistical Approaches for Reconstructing Random Coefficients in the Problem of Stochastic Modeling of Air–Sea Heat Flux Increments

This paper compares two statistical methods for parameter reconstruction (random drift and diffusion coefficients of the Itô stochastic differential equation, SDE) in the problem of stochastic modeling of air–sea heat flux increment evolution. The first method relates to a nonparametric estimation of the transition probabilities (wherein consistency is proven). The second approach is a semiparametric reconstruction based on the approximation of the SDE solution (in terms of distributions) by finite normal mixtures using the maximum likelihood estimates of the unknown parameters. This approach does not require any additional assumptions for the coefficients, with the exception of those guaranteeing the existence of the solution to the SDE itself. It is demonstrated that the corresponding conditions hold for the analyzed data. The comparison is carried out on the simulated samples, modeling the case where the SDE random coefficients are represented in trigonometric form, which is related to common climatic models, as well as on the ERA5 reanalysis data of the sensible and latent heat fluxes in the North Atlantic for 1979–2022. It is shown that the results of these two methods are close to each other in a quantitative sense, but differ somewhat in temporal variability and spatial localization. The differences during the observed period are analyzed, and their geophysical interpretations are presented. The semiparametric approach seems promising for physics-informed machine learning models.

An exact asymptotic solution for a non-Newtonian fluid in a generalized Couette flow subject to an inclined magnetic field and a first-order chemical reaction

&lt;abstract&gt;&lt;p&gt;Understanding generalized Couette flow provides valuable insights into the behavior of fluids under various conditions, contributing to the advancement of more accurate models for real-world applications including tribology and lubrication, polymer and food processing, water conservation and oil exploration, microfluidics, biological fluid dynamics (blood flow in vessels), and electrohydrodynamic, and so on. The present study provided the exact asymptotic solution for the generalized Couette flow of a non-Newtonian Jeffrey fluid in a horizontal channel immersed in a saturated porous medium.The governing partial differential equations were transformed into a dimensionless form using the similarity technique and the resulting system of equations is solved by the Perturbation technique, as well as the method of the separation of variables, and computed on MATLAB (ode15s solver).The behavior of fluid velocity was investigated and presented through 2-D and 3-D graphs for two cases (ⅰ) when the implication of the magnetic field was strengthened and (ⅱ) when the magnitude of the magnetic field was fixed but its degree of inclination was altered. The first-order chemical reactions and thermal radiation were also considered. Additionally, the effect of numerous emerging quantities on momentum, temperature, and concentration contours characterizing the fluid flow was depicted graphically and discussed. Furthermore, the skin friction (at different angles of inclination and magnetic strength), Nusselt number, and Sherwood number (at different time intervals) were evaluated at both boundaries and presented tabularly. The findings revealed that there was a decrease in the velocity profile with an increasing degree of inclination and strength of the magnetic field. Moreover, we observed an increment in thermal and mass flux when it was measured over time at both of the channels. Also, the outcomes predicted an oscillatory nature of shear stress at both of the boundries.&lt;/p&gt;&lt;/abstract&gt;

Optimum design and analysis of solar pump with the help of genetic algorithm, a MATLAB tool, and RSM tool at minimum cost

AbstractIn this research paper, a well‐performing solar pump at the minimum cost of project life is designed and installed. Initially, the capacity of submersible pumps and discharge have been determined based on the water requirement of the crop and the size of the field. The total number of solar panels, inverter size, and motor pump system have been designed based on the law of conservation of energy. The two optimization techniques genetic algorithm (GA) and response surface methodology (RSM) have been used for analyzing the pump performance parameters and total cost. The GA tool has been used to determine the optimum tilt angle on which responses namely solar flux, solar panel efficiency, exergy, and pump efficiency should be maximum. Moreover, the performance of the solar pump at the optimum tilt angle has been compared with the 28° fixed tilt angle (latitute of location). For the experimental study solar pump experimental setup of 5 hp power has been installed in Faculty of Engineering and Technology, MJP Rohilkhand University at 28.36°N, 79.43°E. The total cost of the solar pump has been optimized with the help of RSM based on the discharge and head of the solar pump. The new optimization approach reduced the levelized cost of electricity (LCOE) from 0.041 to 0.035 $/kWh and the payback period is reduced from 4 to 3 years. The annual increment in average solar flux and overall efficiency has been recorded to be from 606 to 697 W/m2 and 11% to 14% respectively.

Experimental measurements of laminar burning velocity of premixed propane-air flames at higher pressure and temperature conditions

This paper presents laminar burning velocity (LBV) measurements of premixed propane-air flames simultaneously at higher mixture pressure (1-5 atm) and temperature (350-630 K) conditions over mixture conditions (ϕ = 0.7-1.3) utilizing the externally heated diverging channel (EHDC) method. The maximum LBV was observed at ϕ = 1.1 for all pressure and temperature conditions. The non-monotonic behavior of the temperature exponents was noted with the minima at ϕ = 1.1. The pressure exponent (β) variation was observed to be parabolic with the maxima at ϕ = 1.0. The current measurements are then compared with the literature results, and the detailed kinetic model predictions of Qin mech, San Diego mech, and USC mech II. The present LBV measurements are in a better match with the mechanism predictions of San Diego mech at the majority of mixture and pressure conditions. The current measurement suggests the variation of temperature exponent (α) as a function of pressure ratio, and pressure exponent (β) as a function of temperature ratio for different mixture conditions (ϕ). A revised power-law correlation for α and β variations is also suggested as, Su=Su0TuTu0∝0+∝11-PuPu0PuPu0β0+β11-TuTu0. The sensitivity analysis reveals a significant increase (≈ 45%) in negative sensitivity for the chain termination reaction H + CH3 (+M) ↔ CH4 (+M) (R56), with a rise in pressure and temperature at all mixture conditions. The reaction pathway analysis indicates a maximum increment in elemental flux (≈ 305 %) in the formation of ethane (C2H6) from its predecessor methyl radical (CH3), due to enhanced pressure and temperature conditions.

Highly water permeable ‘reverse osmosis’ polyamide membrane of folded nanoscale film morphology

Desalination membrane is playing a major role to meet the need of clean water for human, agricultural and industrial uses. Engineering of the membrane structure for enhancement of water permeability while maintaining salt rejection efficiency would bring benefits of high throughput product water and quality. We explored fabrication of ‘reverse osmosis’ desalination membrane by use of self-assembled sodium dodecyl sulphate surfactant micelle as structure directing agent in ordering reactive monomers towards an organized network leading to thin-film membrane deposition over the nodular structure of polysulfone porous substrate of 50–100 nm. Using small-angle neutron scattering, we studied the change of nanoscale self-assemblies of micellar structure depending on the surfactant concentration, which influenced on the formation of the membranes of improved performance. We found that the larger micellar structure (ellipsoidal) assisted fabrication gave the membrane with the best improvement in the desalination performance in terms of water flux increment by ∼180 % and further pore size refinement with increment in salt-rejection selectivity by ∼5 %.

Thermal performance of a radial-rotating oscillating heat pipe and its application in grinding processes with enhanced heat transfer

Grinding difficult-to-machining materials can generate massive heat. The heat generated by grinding easily accumulates in the grinding zone (the contact area between workpiece and wheel), leading to high temperatures, which harms the grinding quality and efficiency. Radial-rotating oscillating heat pipe (RR-OHP) can achieve high thermal performance and can potentially to apply in grinding with enhanced heat transfer. The RR-OHP is supposed to be designed in the grinding wheel to improve the heat transport ability, in this case, grinding heat can transfer out directly via the grinding wheel. RR-OHP needs to obtain high thermal performance under radial rotations, while the related research is still insufficient. In this paper, the influence of centrifugal acceleration (0 – 1620 m/s2), working fluid properties (methanol, DI water), and heat flux (1.5 × 104 – 4 × 104 W/m2) on the heat transport capacity are studied. A prototype of a grinding wheel combined with RR-OHPs is developed. A grinding simulation by the wheel is built to demonstrate the enhanced heat transfer of RR-OHPs in grinding process. Results show that the increment of heat flux and centrifugal acceleration can improve the thermal performance of RR-OHPs. The thermal resistance of RR-OHP filled with methanol is smaller than that of RR-OHP filled with DI water. In addition, under the condition that grinding speed of 12 m/s, infeed speed of 360 mm/min, and 1 mm depth of cut, the grinding wheel embedded with 16 RR-OHPs can transfer out 79% of total heat and control the temperature under 262 °C, based on the grinding simulation. On the contrary, the grinding wheel without RR-OHPs transfers only 34% of the total grinding heat, and the temperature reaches up to 766 °C.

Computational Study on Structural and Thermal Behavior of Aircraft Disk Brake Rotor for Different Materials

Brakes are one of the most significant safety systems in an aircraft. The rotor will be exposed to large stresses which result in surface cracking, overheating of brake fluid, seals and other components during the braking process. Thus, one of the main tasks for the design of braking system is to reduce the stress, deformation and surface temperature of the brake rotor. This can be achieved by choosing the right material which will undergo the least thermal stresses. In this research a detailed study of structural and thermal analysis is carried out for disc brake rotor of DHC-6 Twin Otter with different materials. The objective of this research is to provide an efficient material for disc brake rotor which can dissipate heat generated during braking at faster rate and also being structurally safe. The materials chosen for the study are Mild Steel, Grey cast iron, Stainless steel, Cabon-carbon composite and Aluminum silicon carbide MMC. From the structural and thermal analysis it was found that the aluminum silicon carbide MMC disc brake rotor exhibits the superior performance against other materials with a mass of 2.37 Kg, deformation of 0.043617 mm, maximum stress of 167.91 MPa, maximum temperature of 250.85 oC and heat flux of 5.2043 W/mm2. The mass, stress, deformation and temperature developed in the aluminum silicon carbide MMC rotor is less than the original stainless steel rotor by 61.3%, 3.66%, 6.9% and 35.6% respectively. Similarly, the aluminum silicon carbide MMC rotor provides better heat dissipation as compared to original rotor due to an increment in heat flux by 15.26%.

Optimization of Potential Nanoemulgels for Boosting Transdermal Glimepiride Delivery and Upgrading Its Anti-Diabetic Activity.

Transdermal drug delivery has been widely adopted as a plausible alternative to the oral route of administration, especially for drugs with poor systemic bioavailability. The objective of this study was to design and validate a nanoemulsion (NE) system for transdermal administration of the oral hypoglycemic drug glimepiride (GM). The NEs were prepared using peppermint/bergamot oils as the oil phase and tween 80/transcutol P as the surfactant/co-surfactant mixture (Smix). The formulations were characterized using various parameters such as globule size, zeta potential, surface morphology, in vitro drug release, drug-excipient compatibility studies, and thermodynamic stability. The optimized NE formulation was then incorporated into different gel bases and examined for gel strength, pH, viscosity, and spreadability. The selected drug-loaded nanoemulgel formulation was then screened for ex vivo permeation, skin irritation, and in vivo pharmacokinetics. Characterization studies revealed the spherical shape of NE droplets with an average size of ~80 nm and a zeta potential of -11.8 mV, which indicated good electrokinetic stability of NE. In vitro release studies revealed enhanced drug release from the NE formulation compared to the plain drug. GM-loaded nanoemulgel showed a 7-fold increment in drug transdermal flux compared to plain drug gel. In addition, the GM-loaded nanoemulgel formulation did not elicit any signs of inflammation and/or irritation on the applied skin, suggesting its safety. Most importantly, the in vivo pharmacokinetic study emphasized the potential of nanoemulgel formulation to potentiate the systemic bioavailability of GM, as manifested by a 10-fold rise in the relative bioavailability compared to control gel. Collectively, transdermal NE-based GM gel might represent a promising alternative to oral therapy in the management of diabetes.

New insights into confined diffusion mechanisms of end-capping reagent regulated interfacial polymerization

The permeability and selectivity of polyamide (PA) nanofiltration membranes depend on the physicochemical structure of the active layer including the crosslinking degree, uniformity, microstructure, and thickness. The additive control strategy has been regarded as a successful method to regulate nanofiltration performance. Herein, the functionalized end-capping reagent, sulfanilic acid, as a co-reactive additive is introduced in the aqueous phase to adjust the homogeneity and thickness of polyamide layer by changing the diffusion behavior of the amine and cross-linking degree of nascent membrane. The end-capping reagent regulates the interfacial polymerization process, which can optimize the distribution of charge density and structural characteristics of polyamide layer, and improve the aperture property by a simple one-step method. The PA-10 with a combination structure of the round-like and ridge-and-valley possesses a favorable water permeance of 23.2 L m−2 h−1 bar−1, which has at least 50% increment in flux while retaining the Na2SO4 rejection compared to the PA-0 (without the additives). Furthermore, the mechanism of interfacial polymerization regulated by end-capping reagents has been studied by the Doppler broadened energy spectrum, thermodynamic molecular reactivity, and molecular dynamics behavior. The loose nascent layer generated by end-capping reagents results in confined diffusion of monomer in the aqueous phase, thus favoring the formation of a thin compact separation layer and improving the membrane separation performance. This work elucidates the mechanism of end-capping reagent sulfanilic acid regulating the interfacial polymerization process and the connection between the composition and performance of nanofiltration membranes, which provides guidance for the controllable design of nanofiltration membranes.

Bushfire resistance of external light steel wall systems lined with fibre cement boards

Bushfires/wildfires have become a widespread and frequent occurrence in many parts of the world. With the adverse effects of climate change and the increasing population in the Bushland Urban Interface (BUI)/Wildland Urban Interface (WUI), ensuring adequate bushfire resistance of buildings in bushfire-prone areas has become very important. Improving the safety and integrity of the external building envelope is identified as a solution to minimise the bushfire related building damage and losses. This paper presents the details of bushfire resistance experiments conducted on external Light gauge Steel Framed (LSF) wall systems and the results. These LSF wall systems were externally lined with fibre cement boards and exposed to both bushfire radiant heat and flame zone fire conditions under indoor and outdoor test conditions. The results have shown that the rapid increment of the heat flux led to sudden explosive failure of the wall system whereas the gradual increment of the heat flux resulted in a progressive failure. This study has highlighted the importance of external cladding integrity and thermal shock resistance of building elements to enhance the bushfire resistance of buildings.

A review of nucleate pool-boiling heat transfer in different liquids and nanofluids

The goal of this review is to examine the current state of the art in nucleate pool boiling heat transfer in a variety of different fluids. The review is divided into many sections that discuss heat transfer in pool boiling, such as pool boiling of nanofluids, boiling behavior of water–glycerin combinations, and operational parameters. With the appropriate mixes of hydrocarbons and other commercial liquids, higher heat transfer coefficients may be produced. Coatings of nanoparticles with varying layer thicknesses applied to the heater surface may be optimized to improve heat transfer from the pool to the surrounding water. The heat transfer hypothesis elucidates the peculiarities of each pool’s boiling regime. It is also possible to expand it to flow boiling by combining pool boiling liquid motion with external mechanical force. Other phase transitions, such as condensation, solidification, and melting, can also be described using boiling heat flow processes. Pool boiling performance can be improved by making a variety of adjustments to the heating surfaces as well as by using pure liquids in the water. Improvements can be made to boiling parameters such as the heat flux, the critical heat flux, the heat transfer coefficient, bubble development and departure, and so forth. A nanoparticle addition to a pure liquid or a surface coating on a heating surface can improve heat transfer and boiling properties by increasing the surface area of the liquid. Pool boiling critical heat flux was enhanced with Al2O3-water nano fluid. Authors used three different powder sizes of Al2O3 which were 0.05, 0.3 and 1.0 μm. Addition of alumina particle in water increases the boiling heat flux. Critical heat flux (CHF) was significantly enhanced using Titania and Alumina nano particles in water as compared to pure water. Average size of nano particle used was 85 nm measured by scattering electron microscope. Enhancement in Critical heat flux is due to nano particle coating on heating surface. Characteristics of nucleate boiling are greatly affected by the operating pressure. Miniature flat heat pipe (MFHP) with evaporator having micro grooved heat transfer surface gives 50% increment in critical heat flux at atmosphere pressure whereas this value increases up to 150% at 7.4 kPa pressure. The addition of CNT (carbon nanotube) to the base liquid increases the critical heat flux. Transmission electron microscopy confirms the average size of a nanoparticle as 15 nm. Authors found that by decreasing pressure from atmosphere condition critical heat flux increases to 200% with CNT/water nano fluid as compared to deionized water. SiC-water nanofluids of 100 nm size were experimented with at volume concentrations of 0.001%, 0.001%, and 0.01%. The size of the nanoparticle was confirmed by a scattering electron microscope. Authors concluded that at 0.01% of nano particle enhances critical heat flux to 105%.

PVDF membranes containing alkyl and perfluoroalkyl-functionalized graphene nanosheets for improved membrane distillation

Polyvinylidene fluoride (PVDF) membranes containing hydrophobic graphene nanofillers were prepared and tested for membrane distillation applications. The nanofillers were obtained by a two-step process: 1st) chemical grafting of hydrophobic molecules, either octylamine (OA) or perfluoroctylamine (PFOA), to graphene oxide (GO) nanosheets, and 2nd) chemical reduction of functionalized GO (rGO) to remove unreacted oxygen-containing functional groups. This resulted in OA-functionalized reduced GO (OA-rGO) and PFOA-functionalized rGO (PFOA-rGO). The addition of these nanomaterials to PVDF membranes prepared by the phase inversion process led to an increase in the membrane contact angle, and therefore higher hydrophobicity, as well as an increase in the membrane porosity. When comparing both nanofillers, OA-rGO and PFOA-rGO, the latter was more efficient in achieving higher contact angles due to the presence of fluorine atoms, whereas OA-rGO led to a greater enhancement in membrane porosity as compared to PFOA-rGO. MMMs containing 0.7 wt% nanofiller loadings of OA-rGO and PFOA-rGO achieved the highest water fluxes of 9.1 and 8.8 L m−2 h−1, respectively and salt rejection above 99.9%, which was monitored for at least 162 h of operation for the former. In comparison with pure PVDF (flux of 5 L m−2 h−1), the addition of OA-rGO and PFOA-rGO nanofillers results in a flux increment of 82% and 76%, respectively.

High oxygen production membranes by Ag catalytic surface modified BSCC perovskite

This work shows the preparation, characterisation and oxygen performance of catalytic surface modified Barium Strontium Cobalt Copper (BSCC) perovskite hollow fibres for oxygen separation from air. BSCC hollow fibres were prepared via a phase inversion and sintering method with an outer diameter of ∼ 1.28 mm and a wall thickness of ∼ 0.47 mm. Subsequently, surface modification was carried out by the deposition of Ag nanoparticles as catalyst, resulting in Ag-BSCC hollow fibres. The effect of the catalyst was significant as oxygen fluxes for the Ag-BSCC hollow fibres were always higher than those of the blank BSCC hollow fibre. The Ag-BSCC hollow fibre reached very high oxygen fluxes of 30.6 mL cm−2 min−1. The maximum oxygen flux increment of 19.4 mL cm−2 min−1 over the blank BSCC hollow fibre is one order of magnitude higher than the majority of catalyst surface modified perovskite hollow fibres to date. In addition, the surface modified Ag-BSCC hollow fibre reduced the apparent energy of activation by 46% as compared to the blank BSCC hollow fibre, thus overcoming the rate limiting step of oxygen surface reaction. A mechanism is provided for the high performance of the Ag-BSCC based on three phase transitions of the BSCC perovskite structure as ascertained by high temperature HT-XRD and the oxygen spillover effect of the Ag nanoparticles.

The Stationary Thermal Field in a Multilayer Elliptic Cylinder

An analytical–numerical method for determining the two-dimensional (2D) thermal field in a layer-inhomogeneous elliptic cylinder (elliptical roller) was developed in the article. A mathematical model was formulated in the form of a boundary problem for Poisson equations with an external boundary condition of the third kind (Hankel’s). The conditions of continuity of temperature and heat flux increment were assumed at the inner boundaries of material layers. The eigenfunctions of the boundary problem were determined analytically. Hankel’s condition was subjected to appropriate mathematical transformations. As a result, a system of algebraic equations with respect to the unknown coefficients of the eigenfunctions was obtained. The above-mentioned system of equations was solved numerically (iteratively). As an example of an application of the aforementioned method, an analysis of the thermal field in an elliptical electric wire was presented. The system consists of an aluminum core and two layers of insulation (PVC and rubber). In addition to the field distribution, the steady-state current rating was also determined. The thermal conductivities of PVC and rubber are very similar to each other. For this reason, apart from the real model, a test system was also considered. Significantly different values of thermal conductivity were assumed in individual layers of the test model. The temperature distributions were presented graphically. The graphs showed that the temperature drop is almost linear in the insulation of an electrical conductor. On the other hand, in the analogous area of the test model, a broken line was observed. It was also found that the elliptical layer boundaries are not isothermal. The results obtained by the method presented in this paper were verified numerically.