Features of metastable superheated water atomization when being discharged through convergent-divergent nozzles at different superheat values

Experiments with the metastable superheated water atomization proved the significant increase of the submicron droplets mass fraction at the outlet of convergent-divergent nozzle from 0.45-0.55 to 0.75-0.9 with an increase of the inlet water temperature from170to255°C. Two different approaches to dimensionless treatment of the atomization processdata and determining the boundary of the zone of flashing predominance are compared. The analysis of two approaches to dimensionless treatment of experimental and calculating results concerning transition to predominating role of nucleation in the process of superheated liquid atomization in convergent-divergent nozzles is done.

Specificfeatures of evolution of dense atomized superheated water plumes and peculiarities of its diagnostics

Experimental study of evolution of plumes of atomized metastable superheated water during its discharge through convergent-divergent nozzles is conducted. Dispersion characteristics of dense plumes in micron and submicron droplet diameter ranges are obtained. Theoretical and prediction analyses of different coagulation mechanisms in the considered two-phase flow are performed. The negligible effect of Brown-type coagulation is shown. It is also demonstrated that turbulent coagulation can change the fraction of micron-diameter droplets within 9%. In addition, for the first time, an “inertial” mechanism of coagulation is considered for the studied plumes under the conditions of plume baking in a cocurrent flow or in the ambient air. It can lead to a considerable decrease in the submicron-droplet mass fraction, which is observed in experiments even at a small distance from the nozzle cut. The predicted data are compared with experimental ones obtained at theexperimental setup.

Modeling of vapor bubble growth at subatmospheric pressures

In this paper, the results of numerical calculations of a vapor bubble growth in superheated water at different pressures are presented. Modeling is based on a previously developed by the authors semi-analytical solution. The results are verified by experimental data obtained at atmospheric and subatmospheric pressures. The presented simulation results and experimental data are in good agreement. The advantage of the solution over the earlier ones (based on the thermal growth model) is shown.

Sustainably Processed Waste Wool Fiber-Reinforced Biocomposites for Agriculture and Packaging Applications

In the EU, sheep bred for dairy and meat purposes are of low quality, their economic value is not even enough to cover shearing costs, and their wool is generally seen as a useless by-product of sheep farming, resulting in large illegal disposal or landfilling. In order to minimize environmental and health-related problems considering elemental compositions of discarded materials such as waste wool, there is a need to recycle and reuse waste materials to develop sustainable innovative technologies and transformation processes to achieve sustainable manufacturing. This study aims to examine the application of waste wool in biocomposite production with the help of a sustainable hydrolysis process without any chemicals and binding material. The impact of superheated water hydrolysis and mixing hydrolyzed wool fibers with kraft pulp on the performance of biocomposite was investigated and characterized using SEM, FTIR, tensile strength, DSC, TGA, and soil burial testing in comparison with 100% kraft pulp biocomposite. The superheated water hydrolysis process increases the hydrophilicity and homogeneity and contributes to increasing the speed of biodegradation. The biocomposite is entirely self-supporting, provides primary nutrients for soil nourishment, and is observed to be completely biodegradable when buried in the soil within 90 days. Among temperatures tested for superheated water hydrolysis of raw wool, 150 °C seems to be the most appropriate for the biocomposite preparation regarding physicochemical properties of wool and suitability for wool mixing with cellulose. The combination of a sustainable hydrolysis process and the use of waste wool in manufacturing an eco-friendly, biodegradable paper/biocomposite will open new potential opportunities for the utilization of waste wool in agricultural and packaging applications and minimize environmental impact.

Three-Dimensional Simulation of Vapour Bubble Growth in Superheated Water Due to the Convective Action by an Interface Tracking Method

In this paper, the growth of a rising vapour bubble in superheated water was numerically studied using an advanced interface tracking method, called the InterSection Marker (ISM) method. The ISM method is a hybrid Lagrangian-Eulerian Front Tracking algorithm that can model an arbitrary Three-Dimensional (3D) surface within an array of cubic control-volumes. The ISM method has cell-by-cell remeshing capability that is volume conservative, maintains surface continuity and is suited for tracking interface deformation in multiphase flow simulations. This method was previously used in adiabatic bubble rise simulation with no heat and mass transfers to or from the bubble were considered. This present work will extend the ISM method's application to simulate vapour bubble growth in superheated water with the inclusion of additional physics, such as the convective heat transfer mechanism and the phase change. Coupled with an in-house variable-density and variable-viscosity single-fluid flow solver, the method was used to simulate vapour bubble growth due to the convective action. The forces such as the surface tension and the buoyancy were included in the momentum equation. The source terms for the mass transfer were also modelled in the CFD governing equations to simulate the growth. Bubble properties such as size, shape, velocity, drag coefficient, and convective heat transfer coefficient were predicted. Effects of surface tension and temperature on the bubble characteristic were also discussed. Obtained numerical results were compared against the analytical and past works and found to be in good agreement.