The D2-Law of Droplet Evaporation When Calculating the Droplet Evaporation Process of Liquid Containing Solid State Catalyst Particles

The review presents the D2-law of droplet evaporation, which is used to describe the spraying process involving the evaporation of droplets. This law, the subject of numerous publications, can be successfully applied to describe the droplet evaporation process under various conditions, including the calculations of the process of feeding the boiler with a liquid that contains catalyst particles. To date, not a lot of work has been devoted to this issue. The paper is a continuation of previous research concerning the spraying of liquids with a catalyst, which improves the efficiency of the process. The conducted analysis showed that the experimental data from previously published work are very compatible with the data obtained from the D2-law of droplet evaporation. At the standard speed of about 20 m/s of an aerosol flowing through a dust duct, droplets in the stream should be observed up to a distance of 1 m from the outlet of the apparatus supplying the system. Under such flow conditions, a droplet’s lifetime must be above 0.05 s. The dependence between a droplet’s lifetime and its diameter and temperature was determined. The obtained results confirmed that the effective droplet diameter is above 30 µm. Such droplets must be generated and then fed to the boiler for the catalyst to work properly. This law is an engineering approach to the problem, which uses relatively simple model equations in order to determine the evaporation time of a droplet

Sedimentation Tanks for Treating Rainwater: CFD Simulations and PIV Experiments

The removal of solids is the most important step when treating rainwater. The article evaluates two designs of sedimentation tanks that can be used for the continuous separation of fine particles from water: OS—standard sedimentation tanks, and OW—swirl sedimentation tanks. The tanks were studied by conducting computational fluid dynamics (CFD) modeling and particle image velocimetry (PIV) experiments. The settling process in sedimentation tank was carried out at varying operating flow rates. A tank with a modified structure was used for the tests, where water was supplied by a nozzle placed at an angle. This solution made it possible to obtain a rotational flow that transported the suspended particles towards its wall, where downward axial velocity resulted in the settling of particles. Based on the research, it was observed that the flow patterns showed inward flow at the bottom of the tank and an upward flow and the lifting of the settled particles near the hatch at the bottom. The presented experimental measurements provided detailed insight into flow patterns, and valuable calibration and verification data for further CFD modeling. Traditional PIV techniques are useful in the case of standard design, whereas CFD is invaluable for supporting this work and for investigating the design of novel sedimentation tanks

The Mathematical Model for the Secondary Breakup of Dropping Liquid

Investigating characteristics for the secondary breakup of dropping liquid is a fundamental scientific and practical problem in multiphase flow. For its solving, it is necessary to consider the features of both the main hydrodynamic and secondary processes during spray granulation and vibration separation of heterogeneous systems. A significant difficulty in modeling the secondary breakup process is that in most technological processes, the breakup of droplets and bubbles occurs through the simultaneous action of several dispersion mechanisms. In this case, the existing mathematical models based on criterion equations do not allow establishing the change over time of the process’s main characteristics. Therefore, the present article aims to solve an urgent scientific and practical problem of studying the nonstationary process of the secondary breakup of liquid droplets under the condition of the vibrational impact of oscillatory elements. Methods of mathematical modeling were used to achieve this goal. This modeling allows obtaining analytical expressions to describe the breakup characteristics. As a result of modeling, the droplet size’s critical value was evaluated depending on the oscillation frequency. Additionally, the analytical expression for the critical frequency was obtained. The proposed methodology was derived for a range of droplet diameters of 1.6–2.6 mm. The critical value of the diameter for unstable droplets was also determined, and the dependence for breakup time was established. Notably, for the critical diameter in a range of 1.90–2.05 mm, the breakup time was about 0.017 s. The reliability of the proposed methodology was confirmed experimentally by the dependencies between the Ohnesorge and Reynolds numbers for different prilling process modes

Population genomics of post-glacial western Eurasia.

Western Eurasia witnessed several large-scale human migrations during the Holocene <sup>1-5</sup> . Here, to investigate the cross-continental effects of these migrations, we shotgun-sequenced 317 genomes-mainly from the Mesolithic and Neolithic periods-from across northern and western Eurasia. These were imputed alongside published data to obtain diploid genotypes from more than 1,600 ancient humans. Our analyses revealed a 'great divide' genomic boundary extending from the Black Sea to the Baltic. Mesolithic hunter-gatherers were highly genetically differentiated east and west of this zone, and the effect of the neolithization was equally disparate. Large-scale ancestry shifts occurred in the west as farming was introduced, including near-total replacement of hunter-gatherers in many areas, whereas no substantial ancestry shifts happened east of the zone during the same period. Similarly, relatedness decreased in the west from the Neolithic transition onwards, whereas, east of the Urals, relatedness remained high until around 4,000 BP, consistent with the persistence of localized groups of hunter-gatherers. The boundary dissolved when Yamnaya-related ancestry spread across western Eurasia around 5,000 BP, resulting in a second major turnover that reached most parts of Europe within a 1,000-year span. The genetic origin and fate of the Yamnaya have remained elusive, but we show that hunter-gatherers from the Middle Don region contributed ancestry to them. Yamnaya groups later admixed with individuals associated with the Globular Amphora culture before expanding into Europe. Similar turnovers occurred in western Siberia, where we report new genomic data from a 'Neolithic steppe' cline spanning the Siberian forest steppe to Lake Baikal. These prehistoric migrations had profound and lasting effects on the genetic diversity of Eurasian populations

The Beaker phenomenon and the genomic transformation of northwest Europe

From around 2750 to 2500 bc, Bell Beaker pottery became widespread across western and central Europe, before it disappeared between 2200 and 1800 bc. The forces that propelled its expansion are a matter of long-standing debate, and there is support for both cultural diffusion and migration having a role in this process. Here we present genome-wide data from 400 Neolithic, Copper Age and Bronze Age Europeans, including 226 individuals associated with Beaker-complex artefacts. We detected limited genetic affinity between Beaker-complex-associated individuals from Iberia and central Europe, and thus exclude migration as an important mechanism of spread between these two regions. However, migration had a key role in the further dissemination of the Beaker complex. We document this phenomenon most clearly in Britain, where the spread of the Beaker complex introduced high levels of steppe-related ancestry and was associated with the replacement of approximately 90% of Britain’s gene pool within a few hundred years, continuing the east-to-west expansion that had brought steppe-related ancestry into central and northern Europe over the previous centuries

Identification of the Interfacial Surface in Separation of Two-Phase Multicomponent Systems

The area of the contact surface of phases is one of the main hydrodynamic indicators determining the separation and heat and mass transfer equipment calculations. Methods of evaluating this indicator in the separation of multicomponent two-phase systems were considered. It was established that the existing methods for determining the interfacial surface are empirical ones, therefore limited in their applications. Consequently, the use of the corresponding approaches is appropriate for certain technological equipment only. Due to the abovementioned reasons, the universal analytical formula for determining the interfacial surface was developed. The approach is based on both the deterministic and probabilistic mathematical models. The methodology was approved on the example of separation of two-phase systems considering the different fractional distribution of dispersed particles. It was proved that the area of the contact surface with an accuracy to a dimensionless ratio depends on the volume concentration of the dispersed phase and the volume of flow. The separate cases of evaluating the contact area ratio were considered for different laws of the fractional distribution of dispersed particles. As a result, the dependence on the identification of the abovementioned dimensionless ratio was proposed, as well as its limiting values were determined. Finally, a need for the introduction of the correction factor was substantiated and practically proved on the example of mass-transfer equipment

Methods to improve the efficiency of atomization process in pneumatic nebulizers

Omówiono metody poprawy efektywności procesu rozpylania w nebulizatorach pneumatycznych. Skupiono się na podniesieniu temperatury rozpylanej cieczy oraz dodatkowym napowietrzaniu cieczy w naczyńku nebulizacyjnym. Połączenie tych dwóch efektów w znaczący sposób przyczyniło się do zmniejszenia średniej średnicy kropli, a charakter aerozolu stał się bardziej monodyspersyjny. Ponadto określono wpływ objętościowego natężenia przepływu gazu na proces atomizacji.The paper discusses methods to improve the efficiency of atomization process in pneumatic nebulizers. The studies were directed on increasing the temperature of sprayed liquid and additional aeration of liquid in the nebulizer cup. Combination of these two effects significantly contributes to the decrease of mean droplet diameter and simultaneously the character of aerosol becomes more monodisperse. In addition, the effect of gas volumetric flow rate on the atomization process was determined

Evaluation of pressure-swirl atomizers and a quality of agrotechnical treatment

Porównano wartości średniej objętościowo-powierzchniowej średnicy kropel i wielkości powierzchni międzyfazowej dla rozpylacza z jednym i dwoma króćcami wlotowymi. Przedstawiono także wpływ prędkości przepływu i lepkości cieczy na wielkość kropel. Wartość średniej średnicy kropel maleje wraz ze wzrostem prędkości przepływu i ze zmniejszeniem lepkości cieczy. Korzystniejsze rezultaty (mniejsze średnie średnice kropel i większe powierzchnie międzyfazowe) uzyskano dla rozpylacza mającego jeden króciec wlotowym w porównaniu do rozpylacza z dwoma króćcami wlotowymi.Values of mean volume-surface diameter of droplet and interfacial surface for atomizers with one and two inlet ports are compared in the paper. The effect of flow rate and liquid viscosity is also presented. The value of mean droplet diameter decreases with the increase of flow rate and the decrease of liquid viscosity. The more favorable results (smaller mean droplet diameter and greater interfacial surface) were obtained for the atomizer equipped with one inlet port compared to atomizer with two inlet ports

Emulsification in the atomizer with a swirl chamber

W pracy określono strukturę emulsji wytworzonej w rozpylaczu o stożkowej komorze wirowej. Przeanalizowano wielkości charakteryzujące proces rozpylania. Wartość spadków ciśnienia wzrastała ze wzrostem prędkości przepływu wody i oleju. Zależność kąta rozpylania od prędkości przepływu wody i oleju była nieliniowa. Wzrost prędkości przepływu oleju nie wpływał istotnie na wielkość kropel oleju w wodzie. Wzrost prędkości przepływu wody powodował powstawanie kropel o większych rozmiarach.The structure of emulsion produced in the atomizer with a swirl chamber was determined. The characteristics of aromization process were analyzed. Drop sizes of emulsion increased with the increasing of water phase content, whereas the increasing of oil phase did not significantly affect the emulsion structure. Pressure drop values increased with the increasing of water and oil flow rates. A relationship between the spray angle and water and oil flow rates represented a non-linear character. The increase of oil flow rate did not significantly affect the size of oil droplets water. The increase the water flow rate caused a formation of larger droplets