The concentration–temperature dependences of the moisture diffusion coefficient (mass conductivity coefficient) during drying of soya and bean kernels were experimentally obtained and analyzed. The values of the moisture diffusion coefficient were calculated from the experimental drying curves of the studied samples, recorded in the absence of external diffusion resistance using the zonal method, based on solving the linear mass conductivity problem at constant environmental parameters in a regular mass transfer mode. In parallel experiments, changes in the linear dimensions of the samples during drying were recorded. By comparing the drying and shrinkage curves, data on sample size changes during drying were obtained, which were taken into account when calculating the moisture diffusion coefficient. Since the soya and bean samples had a shape close to a bounded cylinder, the moisture diffusion coefficient was calculated using a formula derived from the solution of the mass conductivity problem for a bounded cylinder. The results of the study on moisture diffusion coefficients for soya and beans were compared with similar results for other grain crops, and the shrinkage data were compared with those for high-moisture plant materials: slices of apple, pear, carrot, and beet. The possibility of representing the moisture diffusion coefficient as a function of the drying agent temperature was discussed. The obtained data can be used for analysis and calculation of drying kinetics of soya and bean grains by the theoretical method, i.e., based on the use of thermophysical characteristics of materials without conducting experimental studies on physical modeling of the drying unit under laboratory conditions.
Theoretical ballistic design of a small-caliber laboratory pneumatic launcher for accelerating projectiles has been carried out. Prototypes of the pneumatic launcher components have been manufactured, and the structure has been assembled. A series of model experiments on projectile launch using compressed air as the working gas at different initial pressures has been performed. The main ballistic parameters of the launch were recorded using modern measuring and recording equipment. A detailed numerical gas-dynamic analysis of the fast processes accompanying the launch has been conducted. The discrepancy between the calculated and experimental muzzle velocity values did not exceed 2
This study focuses on the Cu (copper)–kerosene nanoparticles in a magnetohydrodynamic mixed convective flow at a stagnation point of a Sisko fluid in a stretched cylinder. The influence of heat source, Arrhenius energy, and heat radiation are considered. To convert dimensional nonlinear equations to a nondimensional form, perfect similarity variables are chosen. After that, dimensional-free equations are solved by applying the bvp4c numerical approach. Numerical outcomes of dimensionless fluid velocity, skin friction, concentration, temperature, rate of heat and mass transport, for some factors are presented graphically. Observation reveals that the curvature parameter raises the velocity profile and rate of mass transfer. Fluid concentration is enhanced by an energy activation parameter. The velocity ratio parameter and Prandtl number reduce fluid temperature. Furthermore, the heat transfer rate for kerosene-based oil is faster in the presence of Cu nanoparticles than in their absence. Also, a table is used to compare the current computed results with the previous ones.
Modern space technology typically requires structures operating under intense, often extreme, thermal conditions since the trend in technological development is toward an increasing number of critical, heat-loaded technical objects, with increasingly stringent thermal loading conditions, while simultaneously increasing reliability and service life and reducing material consumption. For spacecraft, thermal management is a critical design aspect, determining key design and engineering decisions. Highly porous thermal insulation materials with low thermal conductivity are widely used in thermal protection structures for modern space technology. These materials typically have an open-pore structure. This means that the thermophysical properties of these materials are significantly dependent on the gas pressure of the environment in which the thermal protection structures based on them operate. It can also be seen that as ambient pressure increases, the thermal conductivity coefficient increases more rapidly. The overall objective of this work is to develop a set of experimental and mathematical tools for a system of identifying the properties of highly porous materials operating under not only changing thermal loads but also variable pressure. This section of the work is devoted to processing experimental data to determine the dependence of the thermophysical properties of fibrous materials on temperature and pressure, as well as to analyzing the computational efficiency of the developed algorithms.
An analysis of the refrigeration unit operation using a water–LiBr mixture and an alternative methanol–LiBr mixture was carried out. The refrigerant transfer through the membrane wall was simulated in order to construct a mathematical model of the working substance separation. The advantages and disadvantages of using these mixtures in refrigeration units were revealed. The prospects of searching for new mixtures in order to increase the efficiency of refrigeration units and expand their operating temperature ranges are shown.
