Increasing Volume Fraction Research Articles

Cardiovascular effects of lactate in healthy adults

BackgroundLow-volume hypertonic solutions, such as half-molar lactate (LAC), may be a potential treatment used for fluid resuscitation. This study aimed to evaluate the underlying cardiovascular effects and mechanisms of LAC infusion compared to sodium-matched hypertonic sodium chloride (SAL).MethodsEight healthy male participants were randomized in a controlled, single-blinded, crossover study. Each participant received a four-hour infusion of LAC and SAL in a randomized order. Assessor-blinded echocardiography and blood samples were performed. The primary endpoint was cardiac output (CO) measured by echocardiography.ResultsDuring LAC infusion, circulating lactate levels increased by 1.9 mmol/L (95% CI 1.8–2.0 mmol/L, P < 0.001) compared with SAL. CO increased by 1.0 L/min (95% CI 0.5–1.4 L/min, P < 0.001), driven primarily by a significant increase in stroke volume of 11 mL (95% CI 4–17 mL, P = 0.002), with no significant change in heart rate. Additionally, left ventricular ejection fraction improved by 5 percentage points (P < 0.001) and global longitudinal strain by 1.5 percentage points (P < 0.001). Preload indicators were elevated during SAL infusion compared with LAC infusion. Concomitantly, afterload parameters, including systemic vascular resistance and effective arterial elastance, were significantly decreased with LAC infusion compared with SAL, while mean arterial pressure remained similar. Indicators of contractility improved during LAC infusion.ConclusionsIn healthy participants, LAC infusion enhanced cardiac function, evidenced by increases in CO, stroke volume, and left ventricular ejection fraction compared with SAL. Indicators of contractility improved, afterload decreased, and preload remained stable. Therefore, LAC infusion may be an advantageous resuscitation fluid, particularly in patients with cardiac dysfunction.Clinical trial registrationshttps://clinicaltrials.gov/ct2/show/NCT04710875. Registered 1 December 2020.

Electric Conductivity Transitions of Water-Absorbable Polybenzimidazole Films.

Transitions seen in the electric properties of water-absorbable poly(2,5-benzimidazole) (ABPBI) films were confirmed by electric conductivity, dielectric constant, and time-domain nuclear magnetic resonance (NMR) measurements. The electric resistance of the films was measured at room temperature using a high-resistance meter, and the dielectric constant at room temperature was measured using an LCR meter in the frequency range of 90 Hz to 8 MHz. The water absorption ratio at equilibrium absorption for the films was 37%, which corresponded to a volume fraction of water of 0.33. The electric conductivity of the films without water absorption was ~1014 S·cm-1, and it increased to ~1010 S·cm-1 with increasing volume fraction, showing a percolation threshold at a volume fraction of 0.025, and remarkable transitions at volume fractions of 0.075 and 0.135. The dielectric constant of the films without water absorption was 3.4, and it increased to 8.1 with increasing volume fraction, showing a transition only at a volume fraction of 0.135. Above a volume fraction of 0.075, where a transition in conductivity was observed, there were two relaxation times at 18-31 μs and 20-93 μs, as determined from the time-domain NMR, and these relaxation times increased with increasing volume fraction. The longer relaxation time increased significantly at a volume fraction of 0.072, which was close to the volume fraction of the transition seen in conductivity. The relationship between the chain mobility of ABPBI and the deterioration in electric insulating properties is discussed.

Evaluation of facings and sandwich properties of carbon fiber/epoxy-PVC foam sandwich composites: Comparison of VARI co-cure and precure manufacturing methods

The manufacturing process of sandwich composites using vacuum-assisted resin infusion (VARI) can be achieved in a one-step infusion process (co-cure). The purpose of this study is to evaluate the properties of the facing and sandwich composites manufactured by the VARI co-cure method. The sandwich composite was fabricated by VARI co-cure and precure for comparison using carbon fiber-epoxy as the facing and PVC foam as the core material. Thickness measurement, fiber volume fraction test, and tensile test were conducted to evaluate the facing properties. The flexural properties of the sandwiches and the effect of different plies on the facing and sandwich properties were also analyzed. The thickness of the co-cure facing is thicker and more varied than the precure. In addition, for the co-cure sandwich, the vacuum bag side (upper) facing has higher thickness and thickness variation than the mold side (lower) facing. The tensile strength of the co-cure facing is lower than the precure facing, which is 433–490 MPa (upper) and 455–521 MPa (lower) compared to 467–538 MPa (precure). The flexural and shear rigidity of the co-cure sandwich is affected by the side of the facing (upper/lower) exposed to tension or compression normal stress as a result of differences in facing properties on both sides. The specific flexural stiffness of the co-cure sandwich was lower by 17.09–45.19 MN-cm5/g compared to the precure of 16.86–46.83 MN-cm5/g due to a combination of increased flexural rigidity and the addition of density to the co-cure sandwich. Increasing facing plies from 2 to 6 plies results in an increase in facing thickness (166%) and thickness variation (477%), an increase in the fiber volume fraction of facing (11%), resulting in an increase in tensile modulus (12%) and strength (14%) of facing as well as increased stiffness of flexural (339%) and shear (42%) of sandwich.

Quadratic convective slip flow of a viscous dissipative Casson C2H6O2$C_{2}H_{6}O_{2}$—Diamond nanofluid over a stretching sheet

AbstractThe present study explores the slip flow properties of a Casson ethylene glycol ‐diamond (spherical‐shaped particle) nanofluid across a stretched sheet, taking into account the effects of viscous dissipation, nonlinear (quadratic) convection, and the presence of space‐temperature dependent heat sources. The inquiry solves the strongly complicated partial differential equation (PDE) regulating the flow dynamics using an implicit Crank‐Nicolson approach. This is essential because it helps explain how nonlinear convective dissipation affects flow and heat transfer characteristics. In particular, a critical factor is the interaction between viscous dissipation and intense nonlinear convection against the heat source. Additionally, the evaluation prioritizes higher Prandtl numbers, adding further importance to the research. Numerical simulations compared against extant literature reveal excellent agreement. Observations indicate that as Prandtl numbers and volume fractions increase, skin friction tends to rise while the Nusselt number tends to decline. However, intriguingly, at , skin friction begins to diminish, whereas while the volume fraction increases, the Nusselt number grows as well. Steady and unsteady results have been captured and discussed in detail through the graphical plots and tables.

Assessing microvascular dysfunction and predicting long-term prognosis in patients with cardiac amyloidosis by cardiovascular magnetic resonance quantitative stress perfusion.

Cardiac involvement in light chain amyloidosis (AL) is the main determinant of prognosis. Amyloid can be deposited in the extracellular space and cause an increase in extracellular volume fraction (ECV). At the same time, amyloid can also be deposited in the wall of small vessels and cause microvascular dysfunction. This study sought to investigate the extent of microvascular dysfunction and its incremental prognostic value in cardiac light-chain amyloidosis (AL-CA) by quantitative stress perfusion. A total of 126 AL amyloidosis patients (61.13 ± 8.46 years, 81 male) confirmed by pathology were prospectively recruited. All subjects underwent cardiovascular magnetic resonance (CMR) with late gadolinium enhancement (LGE), T1 mapping, and stress perfusion on a 3T scanner. ECV and myocardial perfusion reserve (MPR) were measured semi-automatically using a dedicated CMR software. Clinical, laboratory, and CMR parameters were analyzed for their prognostic value in the assessment of AL-CA patients. Mortality-associated markers were analyzed by univariate and multivariable Cox regression. The median follow-up time was 37 (33.6-40.4) months, and 62 patients died. The ECV of survivors was significantly reduced, but the stress myocardial blood flow and MPR were higher (P<0.001). The MPR of the transmural LGE group was significantly lower than that of the no LGE and subendocardial LGE groups (P<0.001). In multivariable analysis, ECV, MPR, and LGE were independently predictive. MPR of >1.5 and ECV of ≤53.6% were associated with improved overall survival, both of which provided predictive incremental value in patients with advanced disease. With equal Mayo staging and degree of ECV, MPR improves assessment of patient survival. ECV and MPR showed additive incremental values and further discriminated prognosis of patients in advanced stages. CMR phenotypes with higher ECV and lower MPR had a worse prognosis.

Phase selection mechanism and eutectic growth kinetics of refractory Nb&lt;sub&gt;81.7&lt;/sub&gt;Si&lt;sub&gt;17.3&lt;/sub&gt;Hf alloy under electrostatic levitation condition

The phase selection mechanism and eutectic growth kinetics of Nb&lt;sub&gt;81.7&lt;/sub&gt;Si&lt;sub&gt;17.3&lt;/sub&gt;Hf alloy are investigated by electrostatic levitation technique. The maximum undercooling of this alloy reaches 404 K(0.19&lt;i&gt;T&lt;/i&gt;&lt;sub&gt;L&lt;/sub&gt;). By analyzing the cooling curves, its hypercooling limit is obtained to be 527 K (0.24 &lt;i&gt;T&lt;/i&gt;&lt;sub&gt;L&lt;/sub&gt;). A critical undercooling of 194 K is determined for the transition of solidification path. Below this undercooling threshold, (Nb) phase firstly nucleates and grows into primary dendrites, resulting in the enrichment of Si and Hf in the residual melt, which is conducive to the formation of the (Nb)+&lt;i&gt;α&lt;/i&gt;Nb&lt;sub&gt;5&lt;/sub&gt;Si&lt;sub&gt;3&lt;/sub&gt; eutectics. Therefore, (Nb)+&lt;i&gt;α&lt;/i&gt;Nb&lt;sub&gt;5&lt;/sub&gt;Si&lt;sub&gt;3&lt;/sub&gt; lamellar eutectics form in interdendritic space. With the increase of undercooling, the growth velocity of primary (Nb) dendritic follows a power function, while the eutectic growth velocity increases slowly. The maximum values of (Nb) dendritic reaches 89.4 mm/s. A modified LKT/BCT model is used to calculate the growth velocity of (Nb) dendrites. The results are in good agreement with the experimental values, indicating that after the LKT model is modified slightly, it can be used to describe the rapid dendrite growth behavior of the (Nb) phase in the Nb&lt;sub&gt;81.7&lt;/sub&gt;Si&lt;sub&gt;17.3&lt;/sub&gt;Hf alloy melt. Meanwhile, the lamellar spacing of (Nb)+&lt;i&gt;α&lt;/i&gt;Nb&lt;sub&gt;5&lt;/sub&gt;Si&lt;sub&gt;3&lt;/sub&gt; eutectics notably decreases to 360 nm at 194 K undercooling. Above the critical threshold, the primary (Nb) dendrites disappear, whereas (Nb) phase and Nb&lt;sub&gt;3&lt;/sub&gt;Si phase nucleate independently in the undercooled liquid and grow into anomalous eutectics. The growth velocity of anomalous eutectic exhibits a power function relationship with the increase of undercooling, with a maximum value of 115.9 mm/s. The interphase spacing of (Nb)+Nb&lt;sub&gt;3&lt;/sub&gt;Si anomalous eutectics is larger than that of (Nb)+&lt;i&gt;α&lt;/i&gt;Nb&lt;sub&gt;5&lt;/sub&gt;Si&lt;sub&gt;3&lt;/sub&gt; lamellar eutectics. Owing to the formation of nanosized eutectics and the increase of volume fraction of (Nb) phase, the alloy fracture toughness at 194 K reaches 21.9 MPa·m&lt;sup&gt;1/2&lt;/sup&gt;, which is 3.4 times as large as that under small undercooling condition.

Effective Thermal Conductivity of Cyclohexane-Based Nanofluids Containing Cerium Dioxide Nanoparticles with Chemisorbed Organic Shell

In the present study, the effective thermal conductivity λeff of nanofluids containing metal oxide nanoparticles with a chemisorbed organic shell was investigated experimentally and theoretically. The model systems synthesized by a continuous-flow hydrothermal method consist of cyclohexane as organic base fluid and dispersed nearly spherical cerium dioxide (CeO2) core nanoparticles with a decanoic acid shell chemically attached to their surface. From the differences between the hydrodynamic diameters of the two core–shell nanoparticle types with (8.6 or 9.1) nm determined by dynamic light scattering (DLS) and the nearly spherical CeO2 core diameters obtained by analytical ultracentrifugation (AUC) and transmission electron microscopy (TEM), an estimation for the thickness of the entire hydrodynamic layer around the particle core in the range of about (1.1 to 1.3) nm could be deduced. Experimental data for λeff of the nanofluids and the thermal conductivity of the base fluid λbf were determined with a steady-state guarded parallel-plate instrument (GPPI) with an expanded (k = 2) relative uncertainty of 0.026 at atmospheric pressure over a temperature range from (283.15 to 313.15) K in steps of 10 K. The measurement results for the thermal-conductivity ratio λeff ·λbf–1 are independent of temperature and increase with increasing volume fraction of the CeO2 core nanoparticles up to about 0.023. It was found that the experimental results can be described by the Hamilton–Crosser model within their experimental uncertainties for all temperatures investigated.

Microstructure and Mechanical Properties of TC4 Titanium Alloy Joint Fabricated By Vortex Flow-Based Friction Stir Welding

AbstractTool wear is a critical challenge in titanium alloy friction stir welding (FSW). Vortex flow-based FSW (VFSW) is a potential solution for this issue because the VFSW process uses a similar material to the base metal as the tool. In this study, TC4 titanium alloy was welded by VFSW for the first time. Parameter optimization of the vortex flow formation is first done, and then the weld formation and the joints’ microstructure and mechanical performance are investigated at different traversing speeds. The results prove that the plunging velocity is the dominant factor in the vortex depth. A lower plunging speed is beneficial for the formation of a deeper vortex. Full penetration is achieved at traversing speeds of 50–120 mm/min at 300 r/min. At welding speed above 130 mm/min, insufficient penetration defects occur. In the heat affected zone, grain coarsening and β-phase volume fraction increase arise, whereas, in the weld nugget, an α+β lamellar structure emerges. Under the optimized parameters, the joint tensile strength is nearly 98% of the base material, but the elongation decreases significantly. The oxides drawn into the weld by the vortex at the junction between the vortex and the base material are the main reason for the small elongation. This study proves that the VFSW process is feasible for titanium alloys.

Probabilistic Assessment of Soil–Rock Mixture Slope Failure Considering Two‐Phase Rotated Anisotropy Random Fields

ABSTRACTSoil–rock mixture (SRM) slopes consist of soils and rocks and are widely distributed globally. In addition to heterogeneity and discontinuity within SRM slopes, the inherent spatial variability can be observed in soil and rock properties. However, spatial variability in rock and soil properties and layouts has not been well considered in the stability analysis of SRM slopes. Additionally, SRM slopes commonly show a rotated anisotropic fabric pattern, while such fabric has rarely been accounted for in SRM slope stability analysis. In this study, a two‐phase rotated anisotropy random field simulation method is proposed to model these spatial variations simultaneously. The proposed approach is then integrated with the finite element method (FEM) to study the impacts of soil volume fraction and bedding dip angle (i.e., rotated anisotropy) on the probability of failure (pf) and failure mode of SRM slopes. It is found that considering only spatially varying layouts can underestimate pf by up to 97% compared to considering both spatially variable properties and layouts. The increase in soil volume fraction significantly improves pf and the likelihood of deep failure. The bedding dip angle greatly influences pf, yet deep failure remains dominant across different bedding dip angles. Furthermore, the failure mode of SRM slopes is more sensitive to the changes in soil volume fraction than to bedding dip angle.

Utilization of Silica from Palm Ash Waste as an Abrasive Material in Brake Friction Composite

The silica element in palm ash has the potential to be an alternative source of silica material to replace mineral silica, making it more environmentally friendly and reducing production costs. This research aims to utilize silica from palm ash waste as an abrasive material in brake friction composites. The silica from palm ash was isolated by a leaching process using 1 M HCl solution at a temperature of 70 °C for 90 minutes. Isolated silica was then characterized by X-ray fluorescence (XRF). The composition of silica was varied by volume fraction (0, 2, 4, and 6%). The mixing process of the powder mixture was conducted using a chopper mixer for 5 minutes, The powder mixture is then hot compressed using uniaxial hot pressing at a pressure of 47 MPa and a temperature of 165 °C for 15 minutes. Post-curing of the samples was carried out at a temperature of 165 °C for 10 hours. The samples were characterized by density, porosity, hardness R-scale, friction coefficient, and specific wear rate. The research results showed that the palm ash was successfully purified with a silica content of 27.3% to 57.2%. Increasing volume fraction of palm ash silica decreases in density and hardness, while porosity increases. The sample with 4% volume of palm ash silica exhibited better friction performance and a lower specific wear rate. Palm ash silica has the potential to replace the silica mineral for brake friction composites.

Prolate spheroids settling in a quiescent fluid: clustering, microstructures and collisions

In this study we investigate the sedimentation of prolate spheroids in a quiescent fluid by means of the particle-resolved direct numerical simulation. With the increase of the particle volume fraction $\phi$ from $0.1\,\%$ to $10\,\%$ , we observe a non-monotonic variation of the mean settling velocity of particles, $\langle V_s \rangle$ . By virtue of the Voronoi analysis, we find that the degree of particle clustering is highest when $\langle V_s \rangle$ reaches the local maximum at $\phi =1\,\%$ . Under the swarm effect, clustered particles are found to preferentially sample downward fluid flows in the wake regions, leading to the enhancement of the settling speed. As for lower or higher volume fractions, the tendency of particle clustering and the preferential sampling of downward flows are attenuated. The hindrance effect becomes predominant when the volume fraction exceeds 5 % and reduces $\langle V_s \rangle$ to less than the isolated settling velocity. Particle orientation plays a minor role in the mean settling velocity, although individual prolate particles still tend to settle faster in suspensions when they deviate more from the broad-side-on alignment. Moreover, we also demonstrate that particles are prone to form column-like microstructures in dilute suspensions under the effect of wake-induced hydrodynamic attractions. The radial distribution function is higher at a lower volume fraction. As a result, the collision rate scaled by the particle number density decreases with the increasing volume fraction. By contrast, as another contribution to the particle collision rate, the relative radial velocity for nearby particles shows a minor degree of variation due to the lubrication effect.

Left Ventricular Hypertrophy in Aortic Stenosis: Early Cell and Matrix Regression 2 Months Post-Aortic Valve Replacement.

In aortic stenosis, the myocardium responds with left ventricular hypertrophy, which is characterized by increased left ventricular mass due to cellular hypertrophy and extracellular matrix expansion. Following aortic valve replacement (AVR), left ventricular hypertrophy regression occurs, but early cellular and extracellular dynamics are unknown. Patients with severe symptomatic aortic stenosis undergoing surgical or transcatheter AVR were prospectively recruited. Pre- and early post-AVR cardiac magnetic resonance imaging assessed left ventricular remodeling, global longitudinal strain, and T1 mapping to determine extracellular volume fraction and volume of cellular and extracellular compartments. In all, 39 patients (aged 71.4±9.8 years, male 79%, aortic valve peak velocity 4.4±0.5 m/s) underwent cardiac magnetic resonance before and at median 7.7 weeks post-AVR. Left ventricular mass index reduced significantly by 15.4% (P<0.001*), primarily driven by cellular compartment regression (18.7%, P<0.001*), with a smaller reduction in the extracellular compartment (7.2%, P<0.001*). This unbalanced regression led to an apparent increase in extracellular volume fraction (27.4±3.1% to 30.2±2.8%; P<0.001*). Although there was no significant change in global longitudinal strain post-AVR, an increase in extracellular volume fraction was associated with worsening of global longitudinal strain (Pearson r=0.41, P=0.01). Mode of intervention (transcatheter versus surgical) did not influence the above myocardial parameters post-AVR (all P>0.05). The asterisk in P values indicates a statistical significance of <0.05. Within 8 weeks of AVR for aortic stenosis, substantial left ventricular hypertrophy regression occurs involving both cellular and extracellular compartments, demonstrating the early myocardial adaptability to afterload relief. Cellular compartment regression is greater than extracellular regression, leading to an apparent increase in extracellular volume fraction. Mode of intervention did not affect degree of reverse remodeling, indicating that both are effective at resulting beneficial changes post-AVR. URL: https://www.isrctn.com; Unique identifier: NCT04627987.

Flexural tensile behaviour of alkali-activated slag-based concrete and Portland cement-based concrete incorporating single and multiple hooked-end steel fibres

In this study, three-point bending tests on notched beams according to EN 14651 have been performed to evaluate the flexural post-cracking behaviour of alkali-activated slag-based concrete (AASC) and Portland cement-based concrete (PCC) incorporating single (3D) and multiple (4D, 5D) hooked-end steel fibres in different volume fractions up to 0.75%. According to the experimental results, the post-cracking residual flexural strength increases with the increase in the fibre volume fraction for each fibre and concrete matrix type. AASC mixes incorporating 3D and 4D fibres show higher values of residual flexural strength for the same crack opening than PCC mixes with the same fibre type and dosage. Only for the mixes incorporating 5D fibres, steel fibre-reinforced PCC (SFRPCC) mixes outperform steel fibre-reinforced AASC (SFRAASC) mixes in terms of post-cracking behaviour. According to EN 14651, the values of the residual strengths and , corresponding to a crack mouth opening displacement (CMOD) of 0.5 mm and 2.5 mm, respectively, and their corresponding characteristic values and , respectively, can be derived from the experimental load-CMOD curves. Following the fib Model Code 2020, each mix can then be classified according to the values of and the ratio. As a result, empirical models have been developed for SFRPCC to predict the values of and and the applicability of such models to SFRAASC is evaluated in this study. Once the values of and are known, tensile constitutive models can be derived according to the fib Model Code 2020 and used as input parameters for finite element modelling. In this study, the accuracy of the code-based constitutive model to predict the flexural behaviour of SFRAASC and SFRPCC is evaluated using the concrete damage plasticity (CDP) model available in ABAQUS. The numerical model based on the tensile stress-strain curve in the fib Model Code 2020 can qualitatively capture the post-cracking behaviour of SFRAASC and SFRPCC incorporating 3D, 4D and 5D at 0.25% fibre volume fraction, despite overestimating their tensile strength. For higher fibre volume fractions, the CDP model, in conjunction with the mode I parameters derived from the fib Model Code 2020, is unable to adequately describe the post-hardening behaviour exhibited by the composites.

Determination of Protein Interaction in Milk Protein Concentrate Powders Manufactured from pH-Adjusted and Heat-Treated Skim Milk.

The influence of heating as a pretreatment on the structural and functional attributes of milk protein concentrate (MPC) powders derived from ultrafiltered/diafiltered (UF/DF) skim milk is under-reported. This research delves into the impact of pH and heat treatment on skim milk's properties before UF/DF and how these changes affect the resulting MPC powders. By adjusting the pH of skim milk to 6.5, 6.8, or 7.1 and applying thermal treatment at 90 °C for 15 min to one of two divided lots (with the other serving as a control), we studied the protein interactions in MPC. Post-heat treatment, the skim milk's pH was adjusted back to 6.8, followed by ultrafiltration and spray drying to produce MPC powders with protein content of 82.38 ± 2.72% on a dry matter basis. MPC dispersions from these powders at 5% protein (w/w) were also evaluated for particle size, viscosity, and heat coagulation time (HCT) to further understand how the protein interactions in skim milk influence the properties of MPC dispersions. Capillary electrophoresis was used to assess the casein and whey protein distribution in both the soluble and colloidal phases. Findings revealed that preheating skim milk at pH 7.1 increased serum phase interactions, while heating skim milk preadjusted to a pH of 6.5 promoted whey protein-casein interactions at the micellar interface. Notably, the D (4,3) of casein micelles was larger for dispersions from milk with a preheated pH of 6.5 compared to other pH levels, correlating positively with enhanced dispersion viscosity due to increased volume fraction. These results support the potential for tailoring MPC powder functionality in various food applications through the precise control of the milk's pre-treatment conditions.

A novel algorithm for generating random fiber distributions for fiber reinforced composites based on lattice partition

AbstractThis paper propose a random fiber distribution generation algorithm based on lattice partition, which addresses the issue of limited increase in fiber volume fraction caused by the random movement of fibers in previous methods. By partitioning the representative volume element (RVE) window into lattices and moving fibers directionally, the proposed algorithm significantly increases the number of fibers within the RVE window. The generated fiber distribution achieves a fiber volume fraction of up to 80%, with an average execution time of 243.4 s. The influence of algorithm parameters on the randomness of fiber distribution is examined through statistical analysis of the generated distributions. Finite element models with various parameters are established to predict the elastic properties of the composites. The average relative error between the predicted values and the experimental results is 8.6%, demonstrating the effectiveness of the proposed algorithm. This algorithm offers a simple and effective approach for generating fiber distributions in the numerical study of the micromechanics of composites.Highlights A new lattice‐partition method is proposed to generate fiber distributions. The fiber volume fraction of generated fiber distribution is up to 80%. The randomness of fiber distribution is analyzed through statistical analysis. The algorithm predicts elastic properties with an average relative error of 8.6%.

Experimental investigation in a forced draft wet cooling tower using aluminum oxide nano particles

Cooling towers are used in industries to remove the excess heat produced by industrial processes and machineries. This cooling phenomenon and its rate can be improved by mixing it with the nanoparticles. The present work focuses on the design and construction of a counter flow forced draft cooling tower with the addition of aluminum oxide (Al2O3) nanoparticles with water to enhance heat & mass transfer. Experiments are performed with the variation of the flow rate of water, water temperature, and the volume fraction of nanoparticles from 0 % to 2 % by volume fraction. The output parameters like coefficient of performance (COP), cooling characteristics coefficient (CCC), Rate of evaporation (ER), cooling tower efficiency & range have been analyzed. Nanofluid properties like viscosity, density & thermal conductivity for different volume fractions have been examined. It is observed that viscosity and thermal conductivity increased with an increase in volume fractions. Viscosity decreased whereas conductivity increased with temperature rise. Results obtained from cooling tower experiments indicated a maximum COP, CCC, ER, efficiency, and range equal to 7.12, 3.54, 3.95 g/s, 75.55 %, and 29.8ᵒC, respectively. For the various volume fractions studied, nanofluid with 2 % outperformed others with higher heat transfer rates and range values. For the 2 % volume fraction of the nanoparticles, make-up water requirements reduced by 76.19 % when it is compared to the normal water without the nanoparticles. Also, it is found that the cooling tower range, heat transfer rate, and efficiency increased by 10 %, 10.2 %, and 4.16 % when nanofluid concentration is varied from 0 % to 2 % by volume for the air velocity and water flow rate of 13 m/s and 3.5 Liters per minute (LPM) respectively.

Thermal performance analysis of a Trombe wall with the multi-row channel PCM wallboard

A novel Trombe wall with the multi-row channel phase change material wallboard (MCPCM-TW) is proposed to enhance the solar energy utilization. The structure contains the glazing, the heat-absorbing layer and the phase change thermal storage layer with several built-in channels, either aligned vertically or horizontally. The thermal performance of the Trombe walls, which consist of the multi-row vertical channel phase change material wallboard (V-MCPCM-TW) and the multi-row horizontal channel phase change material wallboard (H-MCPCM-TW), were investigated numerically in the present research. Meanwhile, the Trombe wall incorporating phase change thermal storage layer without built-in channels also studied in the paper. The results indicate that, the multi-row channel phase change material wallboard effectively enhances the heat storage and release of the phase change thermal storage layer, thereby extending the duration of ventilation and increasing the cumulative heat supply of the rooms equipped with the novel Trombe wall. Specifically, the V-MCPCM-TW has a higher maximum liquid volume fraction during the heat storage. Compared with the Trombe wall incorporating phase change thermal storage layer without built-in channels, the V-MCPCM-TW has a 16 % increase in maximum liquid volume fraction and a 15.5 % increase in cumulative heat supply within a certain period.

Performance of the GH4169 Joint Using a Novel Ni-Based Amorphous Brazing Filler Metal

A novel Ni-Cr-Si-B filler metal (JNi-5) was designed and further fabricated into the amorphous brazing filler metal for joining the GH4169 alloy. The effect of brazing temperature on the microstructure and mechanical properties of GH4169 joints was investigated. The typical microstructure of the joint at 1030 °C is composed of four specific zones: the base metal (BM), heat-affected zone (HAZ), isothermal solidification zone (ISZ), and athermal solidification zone (ASZ). The typical microstructure of the joint is GH4169/(Nb, Mo)-rich boride+(Cr, Nb, Mo)-rich boride/γ(Ni)/Ni-rich boride+γ(Ni)/γ(Ni)/(Cr, Nb, Mo)-rich boride+(Nb, Mo)-rich boride/GH4169. As the temperature increased, the HAZ continued to widen and the ASZ depleted at 1090 °C and 1120 °C. Additionally, the borides within the HAZ coarsened at temperatures of 1090 °C and 1120 °C. At 1030 °C, the fracture path is in the ASZ, and the existence of the brittle phase in the ASZ provides the potential origin for crack growth. The fracture mode is a quasi-cleavage fracture. At 1060 °C, 1090 °C, and 1120 °C, the fracture behavior mainly happened in the HAZ, and the existence of borides in the HAZ provides the potential origin for crack growth. Namely, the shear strength of joints was principally dominated by the brittle precipitations in the HAZ. The fracture mode of these joints is the hybrid ductile. At 1060 °C, the shear strength of the obtained joint is the highest value (693.78 MPa) due to the volume fraction increase in the Ni-based solid solution. Finally, the optimized brazing parameter of 1060 °C/10 min was determined, and the corresponding highest shear strength of 693.78 MPa was obtained owing to the increased content of the Ni-based solid solution in the joint.

Experimental study of solid-liquid two-phase flow field in a centrifugal pump volute under multiple working conditions

In order to study the variation law of the solid-liquid two-phase flow field in the volute of centrifugal pump and the distribution law of the solid particles in the volute, based on PIV technology, the dynamic and static interference flow field of the volute under different flow conditions (30 m3/h, 40 m3/h, 50 m3/h, 60 m3/h, 70 m3/h) and different solid phase volume fractions (1 %, 1.5 %, 2 %) is studied. It is found that with the increase of the solid phase volume fraction, the head and efficiency of the centrifugal pump gradually decrease, and the addition of the solid phase has little effect on the pump head when the solid phase volume fraction is small under the condition of the large flow. The high turbulent kinetic energy area in the volute is mainly concentrated near the outer wall of the volute and the area where the tongue is located. Under the same solid phase volume fraction, the turbulent kinetic energy in the volute increases with the increase of the flow rate. The turbulent kinetic energy in the volute decreases with the increase of the solid phase volume fraction. The absolute velocity component of the flow field in the volute is significantly affected by the flow condition.

Preparation of Silver Nanoparticles in a Water-in-Oil Microemulsion Stabilized by Ecosurf EH3 and Determination of Their Electrophoretic Mobility.

This work describes a study on the electrophoresis of silver nanoparticles in reverse microemulsions with varying water content. The microemulsion was stabilized using a nonionic ethoxylated surfactant, 2-ethylhexanol triethoxylate (Ecosurf EH3). This study represents the second example of electrophoresis research conducted in media with a low dielectric constant for etoxylated surfactants. The study also determined the boundaries of thermodynamic stability and the conditions required to obtain nanoparticles with a high yield. The hydrodynamic diameter and electrophoretic mobility of nanoparticles were measured using dynamic light scattering and laser Doppler electrophoresis. The study determined the boundary conditions for applying these methods to laser-absorbing samples. The electrophoretic mobility of nanoparticles was found to be dependent on the fraction of water in the range of 2-5%vol. (equivalent to a metal content of 10-25mM), as determined by electrophoresis in a free medium. The increase in volume fraction of water leads to agglomeration of micelles, which causes a decrease in the electrokinetic potential of nanoparticles, likely due to the blurring of the diffuse part of the electrical double layer.