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This paper presents a preliminary study of a novel type of turbulizers based on the jet pump working principle and designed to intensify heat transfer in double-tube heat exchangers. To determine the potential for their use, Computational Fluid Dynamics (CFD) and realizable k-ε turbulence model were applied to four turbulizers differing in the angles and diameters of the nozzle and diffuser. During studies, a number of parameters were determined, including: (i) Euler number Eu, (ii) overall heat transfer coefficient kT and (iii) reduced ratio of heat duty to mechanical power 𝜀r; and then compared with data available for strip turbulizers. The tests yielded the following maximum values of: Eu - 1.5 times higher, kT - 2 times higher, and 𝜀𝑟 - 27 times higher than those obtained by classical strip turbulizers, which indicates the high potential of presented jet pump turbulizers and justifies their further development. [ABSTRACT FROM AUTHOR]

A major limitation of Computational Fluid Dynamics application in modelling devices with complex configuration is generating a numerical mesh that can accurately recreate the fluid domain without exceeding available computational power. To simplify the geometry of the impossible to simulate traditionally Pall rings and brush turbulators, the porous media model was implemented. In this research, we simulated the pressure drop in the double-pipe heat exchanger filled with eleven turbulators of different kinds (including: Pall rings, spiral packing, stamped sheet, brush, spring, and twisted tape). The viscous and inertial coefficients of the porous media were calculated for each turbulator and implemented in the calculations. The results were compared with the collected experimental data, which demonstrated the satisfactory accuracy of this approach. It is concluded that the porous media model performs especially well for the brush and spiral packing turbulators. [ABSTRACT FROM AUTHOR]

Abstract The main aim of the research presented in the paper was to determine the sensitivity of the model describing the flow of the dispersed phase in the spout-fluid bed apparatus operating in a fast circulating dilute spout-fluid bed regime to the way of calculating the normal restitution coefficient during collisions of particles with the wall. On the basis of relevant literature, four models were selected that could be applied to microcrystalline cellulose particles used in the described device: Thornton's, two variants of Jackson-Green, and LWT (Li-Wu-Thornton). The results of the dispersed phase velocity in the draft tube and annular zone of the device obtained from the computer simulations were compared with the experimental data. The LWT model, which accurately reproduces the particle velocity in the draft tube zone, provided the best match with the measured data. Graphical abstract Unlabelled Image Highlights • Discrete phase model with particle-wall interaction is introduced. • The influence of normal restitution model on the flow of particles is analyzed. • Results of Li-Wu-Thornton model are found in best agreement with experimental data. [ABSTRACT FROM AUTHOR]

The main objective of the study was to develop a model describing the flow of particles (cores) in an apparatus operating within the range of the fast circulating dilute spout-fluid bed. The greatest emphasis was placed on the selection of appropriate description of the particle-wall interactions (impact model or fixed values of restitution coefficients). Its influence on the dispersed phase velocity in the draft tube and annulus of the apparatus was investigated. Results obtained from computer simulations were compared with our own experimental data. The use of equations calculating normal and tangential restitution coefficient resulted in a noticeable improvement in the accuracy of results only in the area of the draft tube in relation to the fixed restitution coefficient approach. It was found that the flow hydrodynamics and apparatus geometry favour computing of low restitution coefficients in the annular zone. [ABSTRACT FROM AUTHOR]

The objective of this paper was to verify the applicability of the EE (Euler-Euler) model for the description of hydrodynamics of particle flow in an apparatus with circulating dilute spout-fluid bed, as well as to test the impact of the model parameters, such as interphase momentum coefficient, restitution coefficient and packing limit on the velocity results of the dispersed phase. It was found that the inter-phase momentum exchange coefficient has the greatest impact on the particle velocities in the specific hydrodynamic conditions in the tested apparatus (high velocity of particle circulation, very low volume fraction of the dispersed phase in all zones). It was established that the value of the restitution coefficient considerably affects the granular temperature and the remaining parameters that are relative to it. This, in turn, results in the variations in the determined particle velocities, which are discernible only in the zone of the draft tube. The packing limit affects the value of the radial distribution function, and the increase of its value leads to the increase of the particle velocities. For the optimum set of model parameters (packing limit 0.55, restitution coefficient 0.9, inter-phase momentum exchange model by Gidaspow), the mean calculation error regarding the particle velocities for all initial bed heights was equal to maximum 9% in the zone of the draft tube and 19% in the annulus. The research confirmed the applicability of the EE model for the description of the gas-solid flow in the spout-fluid system with an original design applied for dry coating. The developed model will serve for the future description of the dry coating process. [ABSTRACT FROM AUTHOR]

Abstract: The construction and performance of a new apparatus for coating and encapsulation of particle cores with diameters lower than 1mm are discussed in detail. The process of electrostatic dry powder coating was carried out in a diluted, fast circulating spout-fluid bed. The spatial separation of the draft tube entrainment zone from the coating zone leads to the reduction of effects of particle-to-apparatus wall adhesion and pneumatic nozzles plugging. As a result, the fine product of high quality without aggregates, agglomerates and granules, in a short time (approx. 10min) and at a low temperature (approx. 45°C) was obtained. Coating powder was charged electrostatically and continuously fed to the apparatus column. In order to verify the performance of the device, a number of tests were carried out with the application of materials used for the production of enteric drugs in the pharmaceutical industry. The quality of obtained coats was investigated by microscopic methods and the kinetics of dissolution of color marker in aqueous solutions was determined. As a result of the research, we obtain microcapsules with a constant release rate of the marker substance in alkaline environment, over 25 times faster than in the acid medium, with only 0.31% release of marker in acid solution in 2h, which is a sufficient level for gastric resistance. [Copyright &y& Elsevier]

A hydrodynamic model based on continuity and conservation equations was used to predict flow behavior in a spouted-bed dryer with a draft lube. The Eulerian-Eulerian multi-fluid modeling approach was applied to predict a gas-solid flow behavior. The model was qualitatively validated and the results of simulations were compared with the experimental data published by various researchers. The model predicts How behavior well with fluctuations. circulations of phases, and cluster formations in the loading region, as was observed in experiments. The predicted solids circulation rate and the fraction of gas bypassing were close to experimental values published for various systems. The coarse 2D axisymmetric grid, used in simulations, can handle the main process dependencies with a sufficient accuracy for engineering calculations. [ABSTRACT FROM AUTHOR]

Drying is an integral part in the treatment of grains to maintain the freshness and good quality of agricultural products, while protecting bioactive substances (vitamins, antioxidants). The processing allows long-term and safe storage of products, but is one of the most energy-consuming steps in food production. Reducing drying costs by the proper energy management, including heat recovery and moisture removal from the drying air is the current challenge. The purpose of this review was to present recent innovations in seed and grain drying systems against the background of traditional techniques. The focus was on hybrid methods (microwave-assisted, infrared-assisted and ultrasound-assisted methods), which according to data can reduce non-renewable energy consumption by up to 80%. The implementation of innovations in drying is an important issue considering consumer health and environmental protection. Techniques applied for the exhaust gas purification from nitrogen oxides, sulphur oxides, carbon oxides, or volatile organic compounds by catalytic decomposition are also described. It also points out the possibility of using energy from renewable sources (solar energy, geothermal energy, energy from biomass combustion), minimizing the use of fossil fuels that have a negative impact on the environment. Dissemination of knowledge in this area is necessary for the implementation of innovative solutions on a large scale, which will allow development towards cleaner production. [Display omitted] • Sustainability in drying technology brings environmental and economic benefits. • Hybrid technologies reduce the energy consumptions even by 80%. • Application of enhanced systems increases drying efficiency by 26.5% time reduction. • The use of a catalyst effectively reduces emission of nitrogen oxides by 15–100%. • Seed drying enhances food quality and protects against pest and fungal growth. [ABSTRACT FROM AUTHOR]