Papers by Keyword: Heat

Abstract: The main directions of the economic and social development of the Republic of Azerbaijan envisage technical re-equipment in the ferrous metallurgy industry based on the wide application of progressive scientific and technical achievements. Here, an important place is given to the creation of new resource-saving technological processes and highly efficient equipment. The most important task of increasing the efficiency of obtaining iron from ore materials is to reduce the consumption of metal and energy. It is important to significantly reduce waste and losses during iron ore production by improving the quality of iron ore logs. The task set in the work is related to the conditions of production and remelting of iron ore logs in an electric furnace. Instead of melting metal waste in metallurgical plants, the steels obtained from the melting of metal logs with 95-97% iron content obtained from iron ore by one end processing method are economically very efficient and important issue for the Republic. The implementation of these important national economic issues is possible by solving the processes of drying and burning of iron ore logs, complex optimization, taking into account the limiting factors of the process of choosing rational temperature regimes and the practical application of the obtained results in the industry. The article belongs to the section "Metallurgical Heat Engineering".

Abstract: In previous research problem statement occur in hardness to reach the thermal flux between surfaces during movement. The aim of the present investigation has been conducted to study the thermal behavior of ceramic Al₂O₃ (AL-99) coated on a low carbon steel type 1.0060 by using a thermal flame spray technique. The key methods used is microstructural characterization and comparing between experimental data record and numerical program.SEM showed that the Al₂O₃ coatings have a dense microstructure, lamellar morphology and complex of several phases. The XRD analysis of the coating after the spray showed a majority phase of α -Al₂O₃ rhombohedral structure and secondary phase of γ-Al₂O₃ orthorhombic structure. The experimental data recorded From wear indicate two step, first one corresponds to the phase of accommodation between surfaces (samples/ disc), the contact temperature gradually increases to a value Of 75 °C for both pairs, the second step , we could remark from experimental and numerical simulation, it reach 95°C for experimental test and 85 for numerical model.The important findings in tribological results showed that the temperature at the contact is related to the shear stress that will result from the increase of the heat flux. From these results it can be said that the measured temperature increases with the increase of the charge and converges with the contact time. The gap of temperature between experimental and numerical results is probably due to the parameter of microstructure, where in experimental porosities improve convection in the area, in contrast the numerical materials don't add this phenomena.

Abstract: The manufacture of ceramic brick goes through the stages of raw material extraction, clay homogenization, material conformation, drying and firing. Drying is the phase that needs greater care, as it involves removing part of the moisture from the brick, in order to preserve its quality after process. This work aims to predict heat and mass transfer in the drying of ceramic bricks in oven using computational fluid dynamics. Considering the constant thermophysical properties, a transient three-dimensional mathematical model was used to predict mass and energy transfer between the material and air during the process. Drying simulations at temperature of 100°C were performed with the air flow in the frontal direction to the ceramic brick holes and the results were compared with those obtained for the air flow in the perpendicular direction to the brick holes reported in the literature. It was found that the position of the brick in relation to the direction of air flow inside the oven affected directly the drying and heating kinetics, and the distribution of temperature and moisture content inside the brick. The positioning of the holes in the brick parallel to the direction of the air flow resulted in reduction at the drying time and, consequently, in energy savings in the process, more uniform drying, and improvement in the product quality.

Abstract: Non-observance of the heat and humidity regime in buildings can lead to significant problems such as the formation of condensation on the internal surfaces of the enclosing structures, which not only destroys the construction of the building but also leads to the formation of mould, fungi that are dangerous for human life and health. In addition, the use of construction or thermal insulation materials in a humid environment increases the energy consumption as a result of which the building's energy efficiency is reduced. In this paper considered the impact of the heat and humidity regime on the construction and thermal insulation materials, and also presents a developed new structure of an air dryer dehumidifier. The results of the study showed that an increase in the moisture content of the construction material by 10%, the thermal conductivity of the material increases from 6% to 60%, which will significantly increase the heating and cooling demand of the building. The developed new structure of the air dehumidifier reduces the humidity of the air, without using additional equipment, or substance such as refrigerant or absorbent. The proposed device significantly reduces capital and operating costs.

Abstract: The fibrillation mechanism of insulin in acid solution has been studied by small angle X-ray scattering (SAXS). It was observed that insulin monomer unfolded in both conditions. Furthermore, in zinc free solution, insulin tend to aggregate on heating start in the first 5 min. The fibrillation through aggregation process continues until 30 min on heating. The similar phenomenon occurs in the presence of zinc ions. The SAXS data suggest that the presence of zinc ions prevent the long cylindrical fibril at the beginning of heating. However, after 20 min heating, the large cylindrical fibril of insulin formed in both conditions.

Abstract: Single pellet heating was considered at natural gas combustion product movement with oxidant flow coefficient of α=1.0 with air and oxygen in unconstrained volume. Physical parameters (density, dynamic and kinematic viscosity) and heat transfer properties (temperature, heat capacity, thermal conductivity, thermal diffusivity) of combustion products correspond to the average composition of gas delivered to the Ural region. Iron-ore pellet average properties were evaluated, based on major pellet plant data. Convection and radiant heat transfer coefficients were determined at pellet heating in natural gas combustion products in a mixture with air and oxygen. It was noted that, at switching to gas burning with oxygen radiant heat transfer to the pellet surface increases significantly, as compared to the convection one.

Abstract: This paper aims to study convective drying of industrial hollow bricks in a tunnel dryer. A transient mathematical model based on the heat and mass conservation equations applied to the air and brick was derived and the numerical solution (finite-volume method) of the governing equations is presented. Predicted and experimental data of the average moisture content and the temperature of the product during the drying process are compared and a good concordance was verified. Numerical results inside the bed confirm an almost null difference between the moisture content along the process. Similar behavior was verified to the product temperature. These results confirm an efficient drying process.

Abstract: Several studies about drying of ceramic materials have been developed in many engineering and fabrication sectors. This process requires high investments and high energy consumption, resulting in high costs to the companies of this sector. In many situations, it is common the use of theoretical solutions that allow, with relative ease and low cost, to change the operational and geometrical conditions of the dryer or object of drying, to obtain the optimized operational conditions. In this sense, this work aims to predict the drying process of a ceramic brick in an oven using the computational fluid dynamics analysis. For a drying temperature of 80°C, the results of the drying and heating kinetics, and the moisture content and temperature distributions of the product and the air and the air velocity and pressure in the oven are shown and analyzed. A comparison between the predicted and experimental data of the average moisture content and temperature of the brick along the process was done and a good agreement was obtained.

Abstract: Freezing is one the most efficient methods for conservation, especially, fruits and vegetables. Cashew is a fruit with high nutritional value and great economic importance in the Northeast region of Brazil, however, due to high moisture content, it is highly perishable. The numerical study of the freezing process is of great importance for the optimization of the process. In this sense, the objective of this work was to study the cooling and freezing processes of cashew apple using computational fluid dynamics technique. Experiments of cooling and freezing of the fruit, with the aid of a refrigerator,data acquisition system and thermocouples, and simulation using Ansys CFX^® software for obtain the cooling and freezing kinetics of the product were realized. Results of the cooling and freezing kinetics of the cashew apple and temperature distribution inside the cashew apple are presented, compared and analyzed. The model was able to predict temperaturetransient behavior with good accuracy, except in the post-freezing period.

Abstract: Food drying is one of the most used methods of preservation. To accurately describe moisture migration within biological products (grains, fruits, vegetables, etc.) during drying and explain the effects of this process on the quality of the material, have been proposed several mathematical models, but few incorporate the phenomena of simultaneous heat and mass transport applied to complex geometry. In this sense, this paper aims to present a mathematical model, based on the thermodynamics of irreversible processes to describe the heat and mass transfer (liquid and vapor) during the drying of bodies with oblate spheroidal geometry. This model was applied to describe drying of lentil, considering the variables transport coefficients and equilibrium conditions at the surface of the solid. Results of the average moisture content, average temperature, liquid flux, vapor flux, and moisture content and temperature distributions inside a lentil kernel during drying process, at different temperatures (40 and 60 oC) were presented and analyzed.