High Volume Concentration Research Articles

Diamond parameter design and assessment of a novel 3D printed diamond grinding wheel with linear cooling channels

To solve the problems of a metal-bonded diamond grinding wheel in grinding hard and brittle material parts, such as easy blockage, poor cooling capacity, and insufficient self-sharpening, a 3D printed diamond grinding wheel with linear cooling channels (GWLCC) was proposed, and its basic parameters were analyzed in this paper. The new grinding wheels with different diamond parameters were prepared by using dual-filament 3D printing technology. The hardness and relative density of the grinding wheels were measured, and the grinding tests of red sandstone were carried out. The experimental results show that high volume concentration and fine granularity of diamond particles are more likely to cause agglomeration behavior, resulting in more pores and cracks, thus reducing the relative density of the grinding wheel and matrix strength, but this is conducive to the exposure of diamond particles. The grinding efficiency of the diamond grinding wheel is positively correlated with the volume concentration and grain size of the diamond. Besides, a test of the grinding performance of GWLCC with different diamond parameters in grinding different brittle-hard materials was carried out, and the suitability of the new 3D printed grinding wheel and its potential to improve grinding performance has been proven. The GWLCC suitable for different hard and brittle materials are summarized.

Thermophysical and Corrosion Inhibitor Evaluation of Graphene, Aluminum Nitride and Barium Titanate Nanolubricants

A newly developed kind of fluid known as nanolubricant is produced by dispersing nanometer-sized materials in base oil. The main issue with nanolubricant is particle stability, which occurs when nanoparticles aggregate due to van der Waals forces. The aim of the study is to evaluate the performance of graphene (GR), aluminium nitride (AlN), and barium titanate (BTO) nanolubricants at 0.05 and 0.1 vol. % concentrations. The stability was identified by using sedimentation photograph capturing method and zeta potential analysis, while KD2 Pro Analyzer was used to measure the thermal conductivity, and the effect of corrosion inhibitor evaluation was measured according to ASTM D130-19. The nanolubricants are prepared by two-step method and undergo ultrasonication process to ensure the nanoparticles are well dispersed in base oil. The results showed that nanolubricants containing 0.05 vol. % nanoparticles are more stable than 0.1 vol. % nanolubricants. Nanolubricants with 0.1 vol. % showed signs of instability based on low zeta potential values. This is due to the fact that the higher the concentration of nanoparticles, the closer the nanoparticles are to one another. This increased van der Waals attraction and potentially causing nanoparticle agglomeration. Improvement in thermal conductivity was obtained with high volume concentration of GR, AlN and BTO nanoparticles. All nanolubricants achieved an ASTM Standard D130 classification of 1a based on the Copper Strip Corrosion Test Standard (slight tarnish, slight colour change). As a result, it was discovered that all prepared samples are effective anticorrosion lubricating oil additives.

Machine learning and numerical simulation research on specific energy consumption for gradated coarse particle two-phase flow in inclined pipes

In deep-sea mining engineering, accurately predicting the energy required per unit length of pipeline to transport a unit mass of solids (dimensionless specific energy consumption, DSEC) is crucial for ensuring energy conservation and efficiency in the project. Based on our previous work, we utilized the machine learning (ML) and the computational fluid dynamics (CFD)–discrete element method (DEM) method to study the transport characteristics and flow field variations of gradated coarse particles in inclined pipes (gradated particles refer to solid particles mixed in specific size and quantity ratios). First, we collect 1185 sets of data from 13 experimental literature, and after analyzing and processing them, an ensemble model based on four other ML models is developed. Both for pure substance particles (PS) and mixed particles (MP), the prediction accuracy of this ensemble model is relatively higher (PSs are spherical particles with uniform size and density, and MPs are particles with different shapes, sizes, and densities). Then, the CFD-DEM process and the operating conditions include low flow velocity with low volume concentration (2 m/s and 2.5%), low flow velocity with high volume concentration (2 m/s and 7.5%), and high flow velocity with low volume concentration (4 m/s and 2.5%). Under conditions of low flow velocity and low concentrations, as well as high flow velocity and low concentrations, the DSEC hardly changes with the variation of the pipe inclination angle. Under low flow velocity and high-concentration conditions, as the pipe gradually becomes vertical, the value of DSEC gradually increases.

The influence of thermal radiation during microwave-assisted freeze-drying of pharmaceutical unit doses

New drying technologies for biologicals have recently been developed to accelerate the time-consuming batch freeze-drying (BFD) process. Among others, microwave-assisted freeze-drying (MFD) has been suggested as a faster and more effective drying technology. In this study, MFD cycles with the microwave radiation switched on and off were performed to assess the contribution of the microwave radiation to drying acceleration. It was found that thermal radiation emitted by the drying chamber walls was predominantly accelerating the drying of monodose placebos rather than microwave radiation. The combination of ultra-low chamber pressure, high thermal heat transfer and a short primary-to-secondary phase transition reduces drying times by more than 80 % compared to conventional BFD. In a second step, a design of experiment approach was used to assess the effect of thermal radiation versus microwave radiation and their combination, together with dosage properties such as fill volume and excipient concentration upon drying rate. The outcome showed the importance of high fill volume and high excipient concentration for an effective microwave contribution to the drying rate. Nevertheless, the drying acceleration for small pharmaceutical dosages with restricted solutes was mainly driven by thermal radiation rather than 2.45 GHz microwave radiation. The inability of ice to convert microwave energy into heat hampers the potential use of microwave freeze-drying for single-dose vaccines.

Non-isochoric stable granular models taking into account fluidisation by pore gas pressure

In this paper, we study non-isochoric models for mixtures of solid particles, at high volume concentration, and a gas. One of the motivations for this work concerns geophysics and more particularly the pyroclastic density currents, whose dense basal parts are precisely mixtures of pyroclasts and lithic fragments and air. They are extremely destructive phenomena, capable of devastating urbanised areas, and are known to propagate over long distances, even over almost flat topography. Fluidisation of these dense granular flows by pore gas pressure is one response that could explain this behaviour and must therefore be taken into account in the models. Starting from a solid–gas mixing model and invoking the compressibility of the gas through a law of state, we rewrite the conservation of mass equation of the gas phase into an equation of the pore gas pressure whose net effect is to reduce the friction between the particles. The momentum equation of the solid phase is completed by generic constitutive laws, specified as in Schaeffer et al. (J. Fluid Mech., vol. 874, 2019, pp. 926–951) by a yield function and a dilatancy function. Therefore, the divergence of the velocity field, which reflects the ability of the granular flow to expand or compress, depends on the volume fraction, pressure, strain rate and inertial number. In addition, we require the dilatancy function to describe the rate of volume change of the granular material near an isochoric equilibrium state, i.e. at constant volume. This property ensures that the volume fraction, which is the solution to the conservation of mass equation, is positive and finite at all times. We also require that the non-isochoric fluidised model be linearly stable and dissipate energy (over time). In this theoretical framework, we derive the dilatancy models corresponding to classical rheologies such as Drucker–Prager and $\mu (I)$ (with or without expansion effects). The main result of this work is to show that it is possible to obtain non-isochoric and fluidised granular models satisfying all the properties necessary to correctly account for the physics of granular flows and which are well posed, at least linearly stable.

Internationally standardized respiratory viral load testing with limited resources: A derivative-of-care calibration strategy for SARS-CoV-2.

SARS-CoV-2 has demonstrated that, in targeted circumstances, viral quantification within respiratory specimens can valuably inform patient management, as well as research. Nevertheless, the pandemic has illustrated concomitant challenges for obtaining high-quality (and broadly comparable) respiratory viral loads. This includes a critical need for standardization and calibration, even though the necessary resources may not always be available for emergent pathogens and non-bloodstream specimens. To these ends, we describe a novel strategy for implementing quantitative SARS-CoV-2 testing with International Unit-based calibration. Earlier in the course of the pandemic-when analytic resources were far more limited-select residual SARS-CoV-2 positive specimens from routine care in our diagnostic laboratory were pooled to formulate a clinically realistic secondary standard of high volume and analyte concentration, which was cross-calibrated to the primary SARS-CoV-2 standard of the World Health Organization. The resultant calibrators were integrated into the original CDC RT-qPCR assay for SARS-CoV-2, whose (now broadened) performance characteristics were defined to generate a test appropriate for both clinical and research use. This test allowed for the quantification of virus in respiratory specimens down to a validated lower limit of quantification of 103.4 IU/ml. By self-formulating calibrators from this derivative-of-care secondary standard, we successfully validated respiratory viral loads without the commercial availability (at that time) of quantitative assays or calibrators. As the SARS-CoV-2 pandemic continues to decline-and even beyond this pathogen-this strategy may be applicable for laboratories seeking to implement viral load testing for nontraditional specimen types despite limited resources.

Enhancing energy harvesting performance of a flat plate solar collector through integrated carbon-based and metal-based nanofluids

Flat Plate Solar Collectors (FPSCs) have been widely employed in the production of renewable energy for a significant period. To enhance their thermal performance, the utilization of nanofluids as heat transfer fluids has emerged as a popular approach. However, many research works were only carried out with conventional metal-based nanofluids. This numerical study investigates the effects of incorporating two carbon nanotubes, namely single-walled carbon nanotube (SWCNT)/water and multi-walled carbon nanotube (MWCNT)/water, on the fluidic and thermal performance of FPSC. The Nusselt (Nu) and Stanton (St) numbers, as well as the frictional characteristics, are measured and compared to those of metal-based nanofluid of alumina (Al2O3)/water at volume concentrations up to 1%. It is found that Nu increases with a higher Reynolds number (Re) while deteriorating at a higher volume concentration. The lowest Nu was recorded for SWCNT/water in the current investigation. The Stanton number increases with a higher volume concentration and decreases with an increase of Re. Notably, the maximum value of 0.001801 is obtained for the SWCNT nanofluid. The outlet temperature decreases maximum for SWCNT/water with the increase of Re and volume concentration while the friction factor decreases with increasing Re and is independent of the type of nanofluids. Maximum thermo-hydraulic performance parameter of 1.48, 1.32 and 1.29 is achieved for SWCNT, Al2O3 and MWCNT, respectively.

Performance investigation of an all glass evacuated tube solar collector with an innovative heat exchanger design using TiO2-H2O nanofluids- an experimental study

ABSTRACT The objective of the current study is to experimentally analyze the thermal performance of an all-glass evacuated tube solar collector (ETSC) with an innovative heat exchanger design by employing TiO2-H2O nanofluid as a heat transmission fluid. Different higher volume concentration (v/c) of TiO2 nanoparticles, i.e. 0.83%, 0.9%, and 0.94% are examined to explore the impact of the nanofluids on the ETSC performance in comparison with only water based ETSC. An outdoor experimental investigation has been carried out using nanofluid at 0.6, 0.7 and 0.8 l/min volumetric rates of flow and its impact using serpentine copper tube coil having uniform pitch distance of 14.3 cm with aluminum fins attached on both side of coil having diameter 12 mm and thickness 1 mm, respectively. The study indicates that thermal performance of ETSC increases with the rise in volumetric flow rate with higher v/c of nanoparticles. For this condition, the temperature rise of water using nanofluid is higher than simple water-based ETSC system, recording an increase in outlet temperature by 4.21%. The maximum thermal efficiency obtained is 52.33% at 0.9% v/c and 0.8 l/min. A comparative assessment between the obtained results and some of the published results reveals that by using serpentine copper coil attached with aluminum fins, with higher concentrations of TiO2 nanoparticles and maintaining higher volumetric flow rate, thermal efficiency of ETSC can be much improved.

Study of the hydraulic parameters of the flow of solid particles in the process of hydrotransport

The article presents the characteristics of transferring solids together with water in the process of hydrotransport at pumping stations, that is, the influence on the distribution of kinematic and dynamic parameters of the flow of hydraulic transport, the description of the pressure dispersed flows in the process of hydrotransport with high volume concentrations and a wide range of particle sizes and densities of solid particles that form mixtures.

Treatment of Boiler Condensate by Ultrafiltration for Reuse.

The generation of water vapor is crucial for the petrochemical industry. In order to protect the boiler from damage, the re-injected water must not contain any suspended matter, especially hydrocarbons. Moreover, it is condensed steam with a temperature close to 100 °C and the unintentional creation or chronic generation of pollution, respectively, that can more or less produce the concentrated pollution. In this context, membrane processes appear promising in order to achieve this reuse and more especially crossflow ceramic membranes. The novelty of this paper is to study the retention of hydrocarbons and suspended solids contained in the condensate hot water of a high-capacity boiler using ceramic ultrafiltration membranes. In total, two ultrafiltration molecular weight cut-offs were used: 50-150 kDa. Several operating parameters were studied such as effluent type (accidental or chronic pollution), temperature, transmembrane pressure, initial volume, and pilot plant size. In all cases, retention of suspended matter was above 90% and residual hydrocarbon concentrations were under 0.1 ppm even for high-volume concentrations. Control of the transmembrane pressure and the molecular weight cut-off of the membrane are key to optimizing the process. Despite the high-volume concentration obtained, the membranes were perfectly regenerated with conventional cleaning procedures.

Investigating thermal performance of combined use of SiO2-water nanofluid and newly designed conical wire inserts

BackgroundThe combined use of augmentation methods plays a significant role to enhance the thermohydraulic performance of thermal systems. This experimental study explores the thermohydraulic performance of a heat exchanger tube with the combined use of SiO2-water nanofluids and newly designed conical wire inserts. MethodsIn this study, a new wire coil insert with different properties from those previously proposed was created. The newly designed inserts were placed in a tube at five distances ranging from 0 to 33.6 mm and SiO2-water nanofluids were used at four volume concentrations (0.5–1.25%). The two step method was used to prepare nanofluids and the experiments were conducted in turbulent flow. Significant findings: The highest heat transfer performance was obtained in the conical wire inserts with pitch ratio of 0, and the least friction loss was obtained in the conical wire inserts with pitch ratio of 4. The best Performance Evaluation criteria was 1.75 at Reynolds number of 3338 and volume concentration of 1.25% for conical wire inserts with pitch ratio of 0. Moreover, the use of nanofluids provided a remarkable heat transfer rate with increased Reynolds number at high volume concentrations, whereas nanofluids at low volume concentrations slightly affected the heat transfer rate and pressure drop. The combination of two techniques presented a promising option for improving the hydrothermal qualities of the heat exchanger.

Stiffness Behavior and Micromechanical Modeling of Asphalt Mastic Composed of Different Fillers

Fillers are known as dust fractions in asphalt mixes having a predominant particle size less than 75 micrometer (μm). Typical filler concentration in an asphalt mix varies from 4% to 12% (by aggregate weight). The effects of filler intrinsic properties on mastic behavior can get magnified with the concentration of filler. Thus, in filler-rich mixes like stone matrix asphalt (SMA), the filler characteristics and concentration can be sensitive factors, playing significant roles in the performance of asphalt mastic and mix. The study considered six different types of fillers to capture the effect of filler characteristics on mastic. The mastics were prepared with a constant filler concentration by volume (F/Bvol=0.49), which was determined by a typical SMA mix design. The fillers were characterized based on their surface area, size distribution, shape, Rigden voids (RV), clay content, and chemical composition. The filler effects on mastic were evaluated based on the stiffness (complex modulus) and stiffness ratio. The weak correlation observed between the mastic stiffness and the fixed and free binder reveals that the RV and filler fixing factor (FFF) can mislead regarding the stiffening potential of filler material. The surface areas by Brunauer–Emmett–Teller (BET) and Blaine’s methods were insufficient to represent the stiffening potential while the stiffness showed a better correlation with the concentration of finer gradations in the filler evinced by a higher coefficient of P10 (percentage passing 10 μ sieve size) and fineness modulus (FM) parameters. Further, the micromechanics based understanding of mastic behavior explains the mastic stiffening phenomenon as the combined effects of adsorbed asphalt layer thickness and interparticle interaction. The linear relation observed between stiffness ratio and newly derived micromechanism stiffening factor (MMSF) indicates that in filler-rich mastics, the stiffness may be improved with a finer sized filler (lower FM) and higher volume concentration. However, the adsorbed layer thickness didn’t show correlation with any of the filler properties considered. The study recommends a limiting value for mastic stiffness in terms of stiffness ratio which is established based on MMSF factor. A limiting value for stiffness of mastic could be significant to avoid dry mixes and subsequent poor fatigue performance.

Experimental studies on thermophysical properties of ethylene glycol/water-based MgO nanofluids

In the present study, the aim is to experimentally measure the isobaric specific heat, viscosity and thermal conductivity of different magnesium oxide (MgO) nanoparticles concentrations dispersed in ethylene glycol/ water mixture with ratio 50:50 vol% as a base fluid. The experiments were performed on 20 nm particle size of MgO nanoparticles suspended in base fluid with different volume fractions from 0.25 to 1% and temperature range from 40 to 120°C. The data results detected that the specific heat capacity of nanofluids reduces as the nanoparticles volume fraction increases but increases as the temperature rises. For all volume concentrations, the dynamic viscosity declines non-linearly with rising temperature. The increase in viscosity related to the base fluid is slightly recognized at low nanoparticles concentrations, while this change is more sensible at higher volume concentrations. Generally, MgO nanofluids showing higher viscosities than the base fluid used. The thermal conductivity of examined nanofluids increases uniformly with increasing the nanofluid sample temperature and nanoparticles volume concentration.

Exploring the Effect of Dispersed Phase on the High Strain Rate Mechanical Response of Nanosilica Dispersions

Shear Thickening Fluids (STFs) constitute a special class of materials which exhibit phase transition from low to high viscosity state when exposed to shearing forces, particularly, when the applied shear rate exceeds a critical value. The last decade has witnessed a mutual symbiotic relationship between STF and high-performance fabrics such as Kevlar®, Dyneema®, Ultra High Molecular Weight Polyethylene (UHMWPE) etc., to produce new light weight and flexible protective materials systems with enhanced knife, stab and ballistic resistant properties than the existing ones. In this study, we explore the effect of particle shape and size on the high strain rate dynamic response of nanosilica dispersions. Shear thickening fluid (STF) was synthesized using fumed silica and spherical nanosilica particles, comprising the dispersed phase, whereas PPG400 (Polypropylene Glycol) was used as the dispersion medium. Ultrasonic homogenization technique was used for the synthesis of STF. The low strain rate rheological characterization was conducted on MCR302 rheometer at 25°C, whereas the high strain rate characterization was performed on inhouse designed and developed SHPB (Split Hopkinson Pressure Bar) apparatus. Fumed silica (FS) particles possess high specific surface area owing to their fractal structure. Therefore, their low molecular weight dispersions exhibit shear thickening behavior thus making them potential candidates for liquid body armour applications. On the other hand, spherical silica dispersions exhibit shear thickening behavior in high phase volume concentrations. Experimental studies showed that spherical silica based STF dispersions exhibited enhanced shear thickening in the low strain rate domain, as well as better mechanical response in terms of higher peak stress under high strain rate compressive loading conditions, during SHPB testing, in comparison to their fumed silica counterpart. Thus, it can be inferred that the mechanical response of nano-silica dispersions is influenced by the shape of the particles constituting the dispersed phase.

Adsorption of Pollutants from Liquid Swine Manure Through the Application of Metabasalt Rock Powder

Adequate animal manure disposal became a challenge in agriculture. Liquid swine waste (LSW), easily used in agriculture, presents disadvantages due to the high volume and low nutrient concentrations. Metabasalt powder, a residue of amethyst mining, was evaluated as an adsorbent agent of nutrients (Cu, Zn, P, and K) from LSW. Seven doses of metabasalt powder were tested in proportion with LSW (0, 4, 10, 20, 40, 80, and 160 kg m−3), and during four contact times (CT) (9, 21, 42, and 84 days) and ions were dosed in the liquid and solid fractions. Copper and phosphorus concentrations in the liquid fraction were lower at 21 days of contact. The lowest concentration of zinc in the liquid fraction was observed at the dose of 10 kg m−3 of metabasalt powder, and at 9 days of CT. The K concentrations in the liquid fraction diminished linearly with the metabasalt doses, in which the major dose presented 51% of K compared to the control. The application of metabasalt as an adsorbent agent reduced the contaminant charge in the liquid fraction of LSW, suggesting safe water disposal while promoting ion accumulation in the solid fraction. The use of metabasalt powder became a useful strategy to make LSW pre-treatment on-farm.

Influence of sediment sources, water mass, and physical processes on the dynamics of flocs at a location between the mouth of a river and the head of a submarine canyon

A field experiment was conducted in the summer of 2011 to obtain detailed process–response data to understand the dynamics of suspended sediment off the Gaoping River mouth near the head of the Gaoping Submarine Canyon in Southern Taiwan. An instrumented tetrapod and a collocated floating platform were used to record the temperature, salinity, current and wave fields. Additionally, the volume concentration (VC) and mass concentration (SSC) of suspended sediments were recorded. Temperature and salinity signals over a tidal cycle distinguished water masses originating from the river plume and the canyon, which alternately dominated the surface dynamics of suspended sediment at the study area. Terrestrial–sourced suspended sediments aggregated into larger flocs, characterized by high VC, SSC, and low effective density values. Conversely, marine–sourced suspended sediments generally had smaller grain sizes, characterized by lower VC, SSC, and high effective densities. In the surface water, the effective density of suspended sediments decreased exponentially with size. In the bottom water, values of VC and SSC were higher under energetic wave conditions and lower under nonenergetic wave conditions, whereas mean size of suspended sediments showed an opposite trend. The hydrodynamics also affected the sediment–water interface, which was reflected in the grain size composition of surficial sediments. The silt and clay content on the seabed was lower under energetic wave conditions and higher under nonenergetic conditions. According to process–responses characteristics, suspended sediments in the bottom water were associated with two regimes: smaller mean size with lower effective densities formed under energetic wave conditions and larger mean size with higher effective densities formed under nonenergetic wave conditions. In the former regime, waves–induced turbulence dominated suspended sediment dynamics by entraining seafloor sediments into the bottom water and aggregating them into microflocs (<~125 μm) and macroflocs (> ~ 125 μm). However, the size distribution of suspended sediment showed a bimodal distribution, and the larger peak is close to the Kolmogorov microscale (around 250 μm). It suggests that strong turbulence associated with significant sediment suspension and flocculation also resulted in disaggregation of macroflocs. As the wave energy dissipated, most of suspended sediments including all fine ones were removed from the bottom water, via flocculation and deposition. Under nonenergetic wave conditions, suspended sediments in the bottom water were contributed from upcanyon water and river plumes, controlled by semidiurnal tidal currents. The size distributions of suspended sediment under nonenergetic conditions were mostly unimodal, with peaks around 100–300 μm, less than the Kolmogorov microscales of turbulence flow (350 μm). Therefore, it could be concluded that turbulence strength plays a key role in flocculation of suspended sediment in the bottom water.

Characterization of scalants and strategies for scaling mitigation in membrane distillation of alkaline concentrated circulating cooling water

Treatment of circulating cooling water via reverse osmosis for water reuse is attractive. However, the discharge of the concentrated circulating cooling water (CCCW) is still an issue to environment. In this paper, direct contact membrane distillation (DCMD) was exploited to treat alkaline CCCW for water reclamation and volume reduction. Results suggested that the alkaline CCCW can be concentrated to achieve high volume concentration factor. DCMD performance decline was primarily due to calcium carbonate (CaCO3) scaling. The CaCO3 deposited on the membrane surface was identified as calcite. Various strategies were adopted to mitigate membrane scaling. Acidization of the CCCW can effectively improve system performance. Additionally, the main scalant transformed from CaCO3 to calcium sulfate (CaSO4) with initial pH decrease. Physical cleaning using deionized water can effectively remove CaSO4 and restore DCMD performance. Compared with commercial antiscalants (sodium polyaspartic acid and amino trimethylene phosphonic acid), EDTA showed excellent scale-inhibition performance. The calcium and magnesium in the CCCW were efficiently pre-removed by chemical softening and ion exchange methods, resulting in improvement of DCMD performance. Given scale inhibition and chemical agent costs, chemical softening was the best strategy to alleviate membrane scaling. Our work suggested that DCMD can be selected as a promising approach for treating the high alkaline CCCW combined with proper strategies to control membrane scaling.

Investigation of effect of type of pigment/extender on the stability of high pigment volume concentration water-based architectural paint

Investigation of effect of type of pigment/extender on the stability of high pigment volume concentration water-based architectural paint

Comparative analysis of CuO-based spiral flow photovoltaic sheet and tube thermal system

The current work investigates experimental characteristics of the PVT system integrated with CuO-water spiral flow heat exchanger and compared with non-cooled PV module. The work describes detailed procedure of nanoparticles preparation, SEM characterizations, and heat extraction characteristics of nanofluid in PVT application. The heat exchanger was pasted at the back of polycrystalline PV module to form PVT system to examine cooling ability, power generation, thermal-electrical yield and overall efficiency at a different volume concentration of CuO nanoparticles at steady mass-flow rate of 0.08 kg/s. From the experiments, it was concluded that the CuO-water nanofluids assisted to lessen surface temperature of PV module by extracting heat that enhanced electrical efficiency by an average of 3.53%. It was also seen that electrical and thermal performance was improved at higher volume concentration and overall efficiency of 30.77% and 36.59% were obtained at 0.01% and 0.03% of volume concentration.

Passive Vaping from Sub-Ohm Electronic Cigarette Devices.

To investigate passive vaping due to sub-ohm electronic cigarettes (e-cigs), aerosol number size distribution measurements (6 nm–10 µm) were performed during volunteer-vaping sessions. E-liquids, with vegetable glycerin (VG) and propylene glycol (PG), with a VG/PG ratio of 50/50 (with nicotine) and 80/20 (without nicotine), were vaped with a double-coil, single aerosol exit hole at 25–80 W electric power, corresponding to 130–365 kW m−2 heat fluxes and with an octa-coil, four aerosol exit holes atomizers, at 50–150 W electric power, corresponding to 133–398 kW m−2 heat fluxes. At the lowest heat flux, lower particle number concentrations (NTot) were observed for the nicotine-liquid than for the nicotine-free liquid, also due to its higher content of PG, more volatile than VG. For the octa-coil atomizer, at 265 and 398 kW m−2, NTot decreased below the first-generation e-cig, whereas volume concentrations greatly increased, due to the formation of super micron droplets. Higher volume concentrations were observed for the 80/20 VG/PG liquid, because of VG vaporization and of its decomposition products, greater than for PG. For the double coil atomizer, increasing the electric power from 40 W (208 kW m−2) to 80 W (365 kW m−2) possibly led to a critical heat flow condition, causing a reduction of the number concentrations for the VG/PG 50/50 liquid, an increase for the 80/20 VG/PG liquid and a decrease of the volume concentrations for both of them. Coherently, the main mode was at about 0.1 µm on both metrics for both liquids. For the other tests, two main modes (1 and 2 µm) were observed in the volume size distributions, the latter becoming wider at 100 and 150 W (265 and 398 kW m−2), suggesting the increased emission of light condensable decomposition products. The lower aerosol emissions observed at 150 W than at 100 W suggest the formation of gas-phase decomposition products. The observation of low-count high-volume aerosols addresses the relevance of the volume metric upon measuring the second-hand concentration of the aerosols released by sub-ohm e-cigarettes.