The droplet deformation in dispersing units of high-pressure homogenizers (HPH) is examined experimentally and numerically. Due to the small size of common homogenizer nozzles, the visual analysis of the transient droplet generation is usually not possible. Therefore, a scaled setup was used. The droplet deformation was determined quantitatively by using a shadow imaging technique. It is shown that the influence of transient stresses on the droplets caused by laminar extensional flow upstream the orifice is highly relevant for the droplet breakup behind the nozzle. Classical approaches based on an equilibrium assumption on the other side are not adequate to explain the observed droplet distributions. Based on the experimental results, a relationship from the literature with numerical simulations adopting different models are used to determine the transient droplet deformation during transition through orifices. It is shown that numerical and experimental results are in fairly good agreement at limited settings. It can be concluded that a scaled apparatus is well suited to estimate the transient droplet formation up to the outlet of the orifice.

The generation of a secondary aerosol after impact, consisting of smaller droplets at a given velocity and mass flow, is relevant for various applications. Thus far, the investigations and modelling approaches on spray impact are based on extrapolation of the single-droplet impingement or empirical correlations. The validity of the models presented is limited to the given experimental setup and conditions such as initial droplet size, velocity and the impact surface characteristics. The aim of this work was to empirically evaluate the spray impact of a two-fluid nozzle on a sphere. A small-scale nozzle was used, which produced a primary aerosol with a mass median diameter of about 12 mu m (liquid-to-gas mass flow ratio = 1, gas pressure: Delta p(G) = 5 bar). After impact on a sphere, a multimodal distribution was observed and a higher mass flowrate of droplets in the small micrometer range (2 and 3 mu m) was produced for a liquid mass flow rate in the range of 1.2-6 kg/h and an atomizing gas mass flow rate of 1-4 kg/h. For easier observation, a geometrically similar, larger nozzle was used, which produced an aerosol with a mass median diameter of about 80 mu m (liquid-to-gas mass flow ratio = 4, gas pressure: Delta p(G) = 1 bar). The measured droplet size after impact is smaller for a lower liquid-to-gas mass flow ratio and increased atomizing gas inlet pressure. Droplet formation mechanisms such as splashing, crown formation and spreading on the sphere surface were observed. A characteristic film with large variations in thickness was generated.

The article contains sections titled: 1 Introduction 2 Fundamentals of Drop Formation 2.1 Dripping and Jet Disintegration 2.2 Sheet or Lamella Disintegration 2.3 Dispersion of Liquids by Gas 3 Spraying Devices and Nozzles 3.1 Single-Substance Pressure Nozzles 3.2 Pneumatic Nozzles 3.3 Flash Spraying and Spraying with Propellants 3.4 Rotary Wheels 3.5 Ultrasonic Spray Generation 3.6 Electrosprays 4 Spray Characteristics 4.1 Spray Evolution and Drop Interactions 4.2 Drop Size Measurement and Drop Size Distributions (DSD) 4.3 Efficiency of Spray Processes and Special Applications References

Emulsions have a wide scope of applications. They can be found in the cosmetic, chemical, pharmaceutical, and food industry. Emulsion properties, such as stability, rheological behavior, and color depend on the droplet size and droplet size distribution (DSD) of the emulsion. High-pressure homogenization (HPH) is mostly used to produce emulsions with droplets smaller than one micrometer. During this process, an emulsion premix with larger droplets is pumped with a pressure of several hundred bar through a disruption unit. In this unit, the characteristic dimension through which the product flows, is significantly reduced. This results in a drastic increase in flow velocity. Thereby, droplets are exposed stresses resulting from laminar, turbulent and cavitating flow patterns, which cause droplet breakup. Nonetheless, the influence of geometrical or process parameters on resulting droplet sizes is still focus of ongoing research. Therefore, the design of a HPH process, which should result in a specific droplet size, is still mostly based on process functions and empirical knowledge. This investigation focuses on the influence of the geometry of the disruption unit, and the process parameters on the local flow pattern and resulting stresses. Previous experimental works have demonstrated that even small changes in the geometry of the disruption unit result in significant changes on the DSD. In addition, CFD simulations have shown that the elongation rate in front of the smallest cross section depends on the geometry of the disruption unit. These higher elongation rates may be responsible for smaller droplets, as they induce elongation into extremely thin filaments (hypothesis of this work). However, due to the very small dimensions of the disruption unit, CFD results (already presented in this ProcessNet section) could not be corroborated up to now. Micro particle image velocimetry (µ-PIV) proposes a promising approach to verify these results. It is a non-intrusive measurement method, which allows an inside view on local HPH process conditions. In this work, a micro particle image velocimetry setup was used to obtain velocity profiles in two optical accessible orifices with varied inlet geometry. The obtained averaged two-dimensional velocity profiles were used to calculate local shear and elongation stresses in the laminar inlet of the orifices. Furthermore, three-dimensional CFD simulations were carried out and the obtained results were compared with the µ-PIV flow patterns.

The versatile use of submicron-sized particles (0.1-1 mu m) requires new manufacturing methods. One possibility for the preparation of submicron-sized particles is spray drying. However, the generation of small droplets at a high production rate and the precipitation of submicron particles are quite challenging. In order to produce a sufficient amount of fine and uniform droplets, a two-fluid nozzle with internal mixing was combined with a cyclone droplet separator. The precipitation of particles was realized with an electrostatic precipitator. Considering the difficulty of electrostatic precipitation concerning explosion risks and to make it capable using organic solvents, the spray dryer was integrated in a pressure resistant vessel. Based on previous experiments, the now presented design is compact and the electrostatic precipitator is shortened. In addition, enhanced drying conditions ensured a controlled and reproducible preparation of submicron-sized particles. Thus, high separation efficiencies were shown. Spray-drying experiments were conducted with the model substance mannitol. With the cyclone droplet separator, a fine and uniform spray with a droplet size smaller 2 mu m was produced. This robust atomizing technique is capable for high concentrations. For a 10 wt% mannitol solution, particles in the submicron range d(50,3) = 0.7 mu m were produced. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

Particle size reduction down to the submicron range (0.1-1 µm) is an effective option to increase the bioavailabilityof low water soluble active pharmaceutical ingredients. According to the Nernst-Brunner equation, the preparation of submicron sized particles increases the specific surface area, thus increases the dissolution rate. Conventional spray drying devices for submicron particles show certain limitations. The main challenge is the preparation of small and uniform droplets during the atomisation step. In this work, fine droplets were generated combining a nozzle with a droplet separator. Therefore, the aerosol is generated with a pneumatic nozzle and is sprayed into a cyclone droplet separator. Depending on the characteristics of the cyclone, droplets larger than the cut-off-size were separated and returned into the liquid feed. The conditioned aerosol at the top of the cyclone separator can then be introduced into the drying chamber. With this concept the usable part is separated, thus no classification process after drying is necessary. The investigations show that the dependencies during atomisation of the droplets size on the liquid-to-gas mass flow ratio µm and the liquid properties (e.g. viscosity) do not apply to the separation step. The conditioned aerosol only depends on the separation characteristics of the cyclone droplet separator. However, the amount of droplets separated is determined by the atomisation step. Hence, the amount of droplets smaller than the cut-off-size can be increased by decreasing the droplet size of the primary aerosol. This is realised by secondary droplet fragmentation. An impact surface causes breakup of the droplets of theprimary aerosol before separation. The investigations show an increased amount of droplets <2µm.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4701

Pressure swirl nozzles equipped with a convex deflection orifice are used for enlargement of the spray angle up to 180 degrees and smaller drop sizes are expected from that operation. The sheet deflection behavior is investigated quantitatively by spray angle measurements for a wide range of operating conditions and nozzles geometries. To achieve proper deflection, the radius of the trumpet contour has to be adapted to the flow conditions generated upstream. Besides the spray angle, the sheet velocity is also known to have a major influence on the drop size and has been measured as compared to common nozzle types. For the deflected sheet, the velocity coefficient may go down to phi approximate to 0.7 compared to plain orifice geometries with phi > 0.9 depending on swirl ratio and viscosity. Finally, the drop size depending on the deflection geometry is measured by laser diffraction and opposed results were found depending on the operating conditions, especially on the viscosity. For low viscosity disturbances were amplified by the deflection orifice and lead to considerably lower breakup length.

This study was dealing with the spray drying of tailored mannitol particles as carriers in dry powder inhalation formulations. A self-constructed spray tower equipped with a laminar rotary atomizer was used to generate very narrow particle-size distributions. A design of experiments with rotation speed and drying temperature as factors was applied for the preparation of a broad set of different mannitol particles. Drying parameters affected particle properties like particle size, particle shape, surface roughness, and flowability significantly. Here, rotation speed was mainly affecting droplet and therefore particle size. Further, it was found that the inner particle temperature, and so the pressure inside the early particle shell, plays an important role during particle formation as emerging water vapor at higher temperatures served for indented particles and rough surface structures. Lower drying temperatures resulted in spherical and smooth particles as the inner temperature remained below the boiling temperature. The occurrence of these particle properties could further be related to mannitol carrier particle flow dynamics as large indented carriers were found to be less flowable than small spherical ones. In general, it was possible to control particle properties by the parameters of the spray drying process.

Nowadays, dry powder inhalation as applied in the therapy of pulmonary diseases is known as a very effective route of drug delivery to the lungs. Here, the system of coarse carrier and fine drug particles attached to the carrier surface has successfully been applied to overcome the cohesiveness of small drug particles. Particle properties of both carrier and drug are known to affect drug dispersion as has widely been discussed for lactose monohydrate and various drugs. This study utilises particle-engineered mannitol as an alternative carrier to discover the effect of mannitol carrier particle properties like particle shape, surface roughness, flowability or particle size on aerodynamic performance during inhalation. Spray drying as a technique to accurately control those properties was chosen for the generation of carrier sizes between 50 and 80 μm and different morphologies and therefore various carrier flowabilities. A set of these carriers has then been blended with different spray dried and jet-milled qualities of salbutamol sulphate as model drug to examine the influence of carrier particle properties on aerodynamic behaviour and at the same time to cover the effect of drug particle properties on particle-particle interactions. This experimental setup allowed a general view on how drug and carrier properties affect the Fine Particle Fraction (FPF) as indicator for inhalation performance and gave the first study to distinguish between mannitol carrier particle shape and surface roughness. Further it was possible to relate carrier particle size and shape to drug accumulation and detachment mechanisms during inhalation as size and shape had the main influence on drug detachment. The addition of jet-milled mannitol fines provided an initial insight into the improving effect of ternary powder blends as has been intensively studied for lactose monohydrate but not for mannitol yet.

The breakup process of primary drops during transition through slots or small openings has been examined frequently in the past. Recent experiments show strong influence of the dispersed-phase viscosity on the deformation of drops at the inlet of orifices that cannot be explained by the equilibrium approach based on capillary numbers or viscosity ratios only. It is necessary to account for the strongly transient character of the process. A quantitative treatment of this behavior based on relationships from the literature and executed with feasible numerical effort is presented. It is shown that the course of the extension rate of the flow and all properties of the system have a major influence on the drop deformation in front of the orifice. The threadlike deformed drops are precursors for the subsequent breakup process downstream.

Deposition of solids within porous materials from a drying solution is an important phenomenon in numerous natural and industrial processes. A profound knowledge about influences of different parameters on the solid distribution in the material is required for an effective targeted impregnation process. Experimental investigations and simulations are used to study the influence of pore structure, drying conditions, and solute concentration on the solid distribution in porous support materials after impregnation and drying. It is found that low drying rates lead to strong solid accumulation at the material surface, whereas high drying rates reduce the solute transport to the surface and result in more uniform solid distributions. A small pore diameter and distribution width reduce solute migration during drying and lead to uniform solid distributions without being influenced by the drying conditions. A higher initial concentration of the impregnation solution causes pronounced surface accumulation, while low initial solute concentrations result in more uniform distributions. Fundamental effects during drying are captured in an existing pore network model by adaption of experimental pore structures and impregnation-drying conditions, resulting in a good general agreement of experiments with simulations.

A downscaled rotary atomizer, operated in the regime of laminar thread breakup, is presented. The atomizer allows for producing dropsizes of 70 -200 mu m and narrow size distribution. Due to the special design of the rotary atomizer the drops are detaching with low velocity and the spray can easily be deflected. The new technology can be applied in small scale spray dryers for the production of powder samples with quantities of several kg h(-1). Pilot scale spray dryers were equipped with this type of atomizer in order to carry out scale-up experiments in small driers, but at particle sizes comparable to production-scale conditions.

Chemie Ingenieur TechnikVolume 87, Issue 8 p. 1081-1082 Vortrag Untersuchung des Sprühbilds an Dralldruckdüsen mit Umlenkkörper an der Mündung zur Sprühwinkelaufweitung J. Kamplade, Corresponding Author J. Kamplade jens.kamplade@bci.tu-dortmund.de Technische Universität Dortmund, Fakultät Bio- und Chemieingenieurwesen, Emil-Figge- Straße 68, 44227 Dortmund, DeutschlandTechnische Universität Dortmund, Fakultät Bio- und Chemieingenieurwesen, Emil-Figge- Straße 68, 44227 Dortmund, DeutschlandSearch for more papers by this authorM. Kelz, M. Kelz Technische Universität Dortmund, Fakultät Bio- und Chemieingenieurwesen, Emil-Figge- Straße 68, 44227 Dortmund, DeutschlandSearch for more papers by this authorProf. Dr. P. Walzel, Prof. Dr. P. Walzel Technische Universität Dortmund, Fakultät Bio- und Chemieingenieurwesen, Emil-Figge- Straße 68, 44227 Dortmund, DeutschlandSearch for more papers by this author J. Kamplade, Corresponding Author J. Kamplade jens.kamplade@bci.tu-dortmund.de Technische Universität Dortmund, Fakultät Bio- und Chemieingenieurwesen, Emil-Figge- Straße 68, 44227 Dortmund, DeutschlandTechnische Universität Dortmund, Fakultät Bio- und Chemieingenieurwesen, Emil-Figge- Straße 68, 44227 Dortmund, DeutschlandSearch for more papers by this authorM. Kelz, M. Kelz Technische Universität Dortmund, Fakultät Bio- und Chemieingenieurwesen, Emil-Figge- Straße 68, 44227 Dortmund, DeutschlandSearch for more papers by this authorProf. Dr. P. Walzel, Prof. Dr. P. Walzel Technische Universität Dortmund, Fakultät Bio- und Chemieingenieurwesen, Emil-Figge- Straße 68, 44227 Dortmund, DeutschlandSearch for more papers by this author First published: 28 July 2015 https://doi.org/10.1002/cite.201550051AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume87, Issue8Special Issue: Jahrestreffen der ProcessNet-Fachgemeinschaft Fluiddynamik und TrenntechnikAugust, 2015Pages 1081-1082 RelatedInformation