Optimisation of a Side Inlet for H2 Entry into an Ultrasonic Spray Pyrolysis Device

An ultrasonic spray pyrolysis (USP) device consists of an evaporation and two reaction zones of equal length, into which an aerosol with a precursor compound enters, and where nanoparticles are formed in the final stage. As part of this research, we simulated the geometry of a side inlet, where the reaction gas (H2) enters into the reaction tube of the device by using numerical methods. Mixing with the carrier gas (N2) occurs at the entry of the H2. In the initial part, we performed a theoretical calculation with a numerical simulation using ANSYS CFX, while the geometries of the basic and studied models were prepared with Solidworks. The inlet geometry of the H2 included a study of the position and radius of the inlet with respect to the reaction tube of the USP device, as well as a study of the angle and diameter of the inlet. In the simulation, we chose the typical flows of both gases (N2, H2) in the range of 5 L/min to 15 L/min. The results show that the best geometry is with the H2 side inlet at the bottom, which the existing USP device does not allow for. Subsequently, temperature was included in the numerical simulation of the basic geometry with selected gas flows; 150 °C was considered in the evaporation zone and 400 °C was considered in the other two zones—as is the case for Au nanoparticle synthesis. In the final part, we performed an experiment on a USP device by selecting for the input parameters those that, theoretically, were the most appropriate—a constant flow of H2 5 L/min and three different N2 flows (5 L/min, 10 L/min, and 15 L/min). The results of this study show that numerical simulations are a suitable tool for studying the H2 flow in a UPS device, as the obtained results are comparable to the results of experimental tests that showed that an increased flow of N2 can prevent the backflow of H2 effectively, and that a redesign of the inlet geometry is needed to ensure proper mixing. Thus, numerical simulations using the ANSYS CFX package can be used to evaluate the optimal geometry for an H2 side inlet properly, so as to reconstruct the current and improve future USP devices.

Evaporation Climate Zonation Based on Observation Data in Indonesia Using Cluster Analysis

Identification of regional evaporation zones is very important because information on the classification of evaporation patterns in an area can be used for various purposes, one of which is knowing the amount of water in the reservoir that is lost due to evaporation. In this study, the evaporation zone in Indonesia was created using cluster analysis. The evaporation data from 127 BMKG observation stations for 6 years from 2014 to 2019 were used after the normal monthly calculation was then standardized with mean = 0 and standard deviation = 1 to ensure that all variables were given the same weight so that it became the 127 x 12 matrix used in the analysis. Hierarchical cluster analysis was chosen to regionalize evaporation. Five different techniques are applied to initially determine the most suitable method for the area. Cluster stability is also tested. It was decided that the Ward method is the most likely to produce acceptable results in this evaporation variable. 3 different classifications of evaporation zones are found in Indonesia. Evaporation zone 1 forms a seasonal cycle with one peak evaporation that occurs with the highest peak occurring in August and the minimum evaporation occurring in February in areas in the northern and central regions of Sumatra island, eastern Kalimantan, parts of Java island, North Sulawesi and West Papua. Evaporation zone 2 forms a seasonal cycle with two peaks that occur in December and March and minimum evaporation occurs in June which is in the southern region of the island of Sumatra, almost the entire island of Kalimantan, a small part of the island of Java, central Sulawesi, the archipelago. Maluku as well as the northern island of Papua. Evaporation zone 3 forms a seasonal cycle with one peak evaporation that occurs in October and the minimum evaporation occurs in June which is in a small area of the island of Central Sumatra, South Kalimantan, the west coast of Sulawesi, and all parts of the island of Nusa Tenggara.

Method for calculating the critical heat flux at pool boiling on structured surfaces

A method of the critical heat flux enhancements at pool boiling using rough structures of various regular and irregular geometries is investigated. The experimental data are compared, and the critical heat flux is calculated since the V. V. Yagov model, which considers the additional inflow of liquid into the evaporation zone due to the action of capillary forces in the porous space. Based on the comparison of experimental and calculated data, it is concluded that the model is not universal for all microstructured surfaces. Recommendations for the calculation are given.

Numerical study of heat and mass transfer in a desalination system

In today’s world the demand for freshwater, to meet the needs of human activities is growing exponentially. As a result, manufacturers are continuing to make progress in the design and production of efficient desalination and cooling units to optimize and reduce the overall cost of production. In this work, we study the numerical study of the evaporation of a thin liquid film dripping by gravity with constant feed rates in a closed rectangular cavity formed by two parallel flat plates. The wall which supports the liquid film is heated by a constant temperature heating, while the other is kept at a constant and uniform temperature to condense the formed vapor. The results obtained show that the heat transfer in the distillation cell is dominated by the latent heat transfer associated with the evaporation. The results also show that the temperature of the film increases slightly for the heating zone and then decreases over most of the plate for the evaporation zone

Mathematical modeling of convection drying process of wood taking into account the boundary of phase transitions

The article deals with constructing and implementing mathematical models of non-isothermal moisture transfer during drying of anisotropic capillary-porous materials, in particular wood, taking into account the movement of the evaporation zone for non-steady drying schedules, as well as to the development of effective analytical and numerical methods for their implementation. An analytical-numerical method for the determination of non-isothermal moisture transfer under non-steady schedules of the drying process has been developed, taking into account the dynamics of the phase transition boundary change. Calculation relationships are established for determining the phase transition temperature taking into account transport gradients and time for which the relative saturation reaches the boundaries of the phase transition.

Increase of the efficiency of an industrial ion-plasma unit MAP-1 in mass production

The article provides an assessment of the influence of the presence of cathode rotation on the deposition rate of the coating for a vacuum-arc evaporator with an extended evaporation zone at the MAP experimental-industrial ion-plasma installation. The analysis of experimental data is carried out, the dependence of the coating deposition rate on the vacuum arc discharge current for an evaporator with an extended evaporation zone is empirically determined. A comparison is made of the rates of deposition of the coating obtained with the rotation of the cathode of the vacuum-arc evaporator and without rotation of the cathode.

IMPLEMENTATION OF THE HIERARCHICAL APPROACHIN THE MATHEMATICAL MODELLINGOF ONCE-THROUGH STEAM GENERATORS

A comprehensive system analysis of a once-through steam generator was carried out as well as a multilevel structure of its model was developed. The application of the procedure of decomposition of a complex object at the initial stages of modeling made it possible to single out multidimensional subsystems of directed action. This makes it possible to use advanced computer simulation software. We distinguished the subsystems of the steam generator as a whole, the subsystem of the steam generator, including the screen tubes, separator, mixer, filter, circulation pump, and connecting pipelines in the resulting structural model. The zones of screen tubes determined by the state of the working medium (heating zone with a single-phase medium, evaporation zone I and evaporation zone II with a two-phase medium), finite-dimensional models of screen tube sections of heating and evaporation zones we considered separately. It was found that the models of zero-level subsystems are described by systems of differential and algebraic equations, between the internal variables of which there is no cause-effect relationship. Any subsystem of the first and higher levels can be represented by a subset of subsystems of the immediately lower levels and a set of oriented connections between them. The principle of recurrent explanation was implemented in the problem of simulating a once-through steam generator. The set-theoretic, matrix and graphical methods are used to describe the relationships between subsystems. It is shown that hierarchical models are forms of description, ready for implementation in high-level programming languages. Systematic analysis of processes, technology and design of a once-through steam generator, as well as the proposed research methodology in the time and frequency domains, the calculation methods and simulation methods used, allows you to select the types and classes of mathematical models, forms of their presentation, as well as software.

Sulfate Attacks on Uncarbonated Fly Ash + Cement Pastes Partially Immersed in Na2SO4 Solution

In this study, the sulfate attack on uncarbonated cement paste partially exposed to Na2SO4 solution was experimentally investigated and compared with that on carbonated specimens with the same exposure regime and uncarbonated specimens without exposure. N2 was used to protect specimens from carbonation throughout the sulfate exposure period. The effects of the water-to-cement (w/c) ratio and the fly ash as cement replacement on the sulfate attack were evaluated. Portland cement paste specimens with different w/c ratios of 0.35, 0.45, and 0.55 or fly ash replacement rates of 10%, 20%, and 30% were prepared. These specimens were partially immersed in 5% Na2SO4 solution for 50 d and 100 d exposure periods. The micro-analysis was conducted to evaluate the effect of the partial sulfate attack on the uncarbonated cement paste using X-ray diffraction (XRD) and thermo-gravimetric (TG) techniques. The results confirmed that, for uncarbonated cement paste, the chemical attack rather than the physical attack is the deterioration mechanism and is responsible for more severe damage in the evaporation zone (dry part) compared with the immersed zone (immersed part). When the effect of carbonation is well excluded, there is an optimal w/c ratio of 0.45 for minimizing the sulfate attack, while incorporating fly ash tends to reduce the sulfate attack resistance.