Journal of Engineering Thermophysics最新文献

We investigate, the impact of Soret and radiation parameters on MHD mixed convection flow of a viscoelastic fluid over a vertical surface. We also study the Hall and induced magnetic field effects. The governing equations are solved by perturbation method. The nature of flow is depicted in graphs. We observe that both the Soret and radiation parameters enhance the velocity of fluid.

In this paper, the effect of sodium lauryl sulfate (SDS) molecules in a homogeneous and already supersaturated aqueous methane solution on the structure of the hydrogen bond network and the kinetics of methane hydrate growth at moderate temperature and pressure is studied by the molecular dynamics method. From calculation of the number of hydrogen bonds and parameters of the tetragonal and torsion orders in comparison with a water + SDS solution and a pure water + methane solution, it is shown that the hydrate growth rate and its crystallinity grow as the methane concentration in the supersaturated solution decreases. In this case, increase in the SDS concentration in a solution with a higher gas concentration leads to phase separation.

In their previous work [1], the authors presented a method of identifying the characteristics of a gaseous medium from measurements of the heat flux absorbed by the surface of a blunt body in a gas flow. The identification problem was stated in an extreme formulation: the sought-for transport properties of a gaseous medium were determined via minimization of the objective function of the estimated and measured heat fluxes absorbed by the surface of a solid body. For minimization of the objective function, the Nelder–Mead method was used in combination with random restarts; the results of testing the algorithm in a model experiment are given. This paper presents the technique of conduction of experiment to verify the method for identification of the gas flow parameters. Experimental results are given for two different gas flow sources.

The industrial component that transfers heat from one fluid to another most frequently uses Shell and Tube Heat Exchangers (STHE). Enhancing the heat transfer efficiency of heat exchangers has garnered more attention as a result of scarce energy resources and high energy expenditures. In STHE, the pressure drop is considered an important issue that causes cracks and economic losses. An essential factor in improving the performance of a heat exchanger with low pressure drop was the angle and distance of the baffles. Several methods were developed to reduce pressure drop and speed up heat transfer. But those methods were not provide a satisfactory pressure drop reduction, so the optimal baffle configuration was still a task in the heat exchanger. In the proposed model, Horse-herd Optimization Algorithm (HOA) based baffle design and neural network based thermal performance prediction arrangement was developed to reduce the pressure drop and predict the rate of transferring heat. Shells and tubes were developed at the corresponding material, inside the shell, a baffle was designed to barrier the flow of cold water. The optimal solution of baffle configuration was solved through HOA, which finds the appropriate baffle’s distance and angle by reducing the pressure drop. After the water flow modelling, the seven key parameters values were observed, and create a dataset. Using this data, a thermal performance prediction system was developed to analyze each period input value to predict the net energy, heat transfer rate, and Nussle number. The proposed model provides 52 Pa pressure drop, 0.59 effectiveness, 0.59 NTU, 417 U, and 92% accuracy. The output of the suggested approach is contrasted with that of other current methods for validation. The proposed model offers a high heat transferring capacity and reduces pressure effects risk.

First-principles calculations based on density functional theory were used to examine the thermoelectric characteristics of BeO and MgO monolayers in the current study. The energy gap range of these two monolayers reveals the insulating properties of BeO and the semiconductor properties of MgO which is in agreement with those of the previously reported results. Following the band structure and related structure parameters the BoltzTrap method was used to determine the electronic transport coefficients based on Boltzmann transport theory. Calculations relating to thermoelectric characteristics are found in this perspective, including those relating to the Seebeck coefficient, the electrical conductivity, the electronic thermal conductivity, electron heat capacity, Hall coefficient, magnetic susceptibility, and figure of merit The crystal structure, internal energy, and electronegativity all have an impact on the characteristics of heat transport since there is a possibility of variable atomic diameters and the different in electron localization function. The MgO monolayer has a somewhat higher figure of merit than BeO due to MgO’s higher electron conductivity in comparison to BeO and its lower electron thermal conductivity values. The new findings can provide a fundamental understanding of thermoelectric transport and related applications for both BeO and MgO monolayers.

If speaking of timely detection of deviations in operation of pumping equipment, there is a problem of the current coverage of the oil well stock with telemetry sensors. Some data analytics, for example, analysis of dynamograms, is still performed manually. The present work attempts to create an automation solution for diagnostics of the condition of well pumping equipment. For sucker-rod pumps, a dynamogram classification model based on a convolutional neural network has been developed, which makes it possible to identify working conditions of a pumping unit. For electric centrifugal pumps (ECPs), a virtual sensor model has been developed based on modern machine learning technologies, which enables prediction of temperature and pressure gradients at the pump intake in the absence of submersible sensors. In the work, we tested a set of classical machine learning algorithms based on linear models and ensembles of decision trees, as well as advanced deep learning methods, e.g., transformers. The virtual sensor models developed are embedded directly into the automated process control system (APCS), and thus technologists and operators can be warned timely, almost in real time, of a possible shortening of the planned time between failures of ECP units and their possible mailfunctioning for various reasons.

The results of testing the popular IQR (Interquartile Range) method for filtering experimental data are presented. It is shown that if the distributions of measured values differ greatly from the Gaussian distribution, this method gives a large error in the statistical characteristics, especially the higher moments. The earlier-developed statistical filtering method can take into account substantial skewness of distributions of measured values and can greatly reduce the filtering error.

The three-dimensional convection in the Earth’s mantle is studied with a well-known mathematical model, which includes the Navier–Stokes equations in the Oberbeck–Boussinesq and geodynamic approximations. Two numerical models of convection are considered. The first is based on the implicit finite-difference schemes of splitting over spatial variables with correction of pressure. The second numerical model is based on the spectral difference method. The numerical models constructed were compared on model problems of convection in a rectangular parallelepiped in a liquid with constant viscosity, corresponding to the convection in the entire mantle of the Earth [1]. The calculation results are in good agreement with the test results.

The present numerical work investigates by means of Constructal Design the influence of the geometry of an inclined passive wall solar chimney on the ventilation performance of an attached room. The main purpose is to maximize the mass flow rate of air in the chimney/attached room. The problem is subjected to two constraints: the chimney and room areas. Three degrees of freedom are investigated: the ratio between the exit and inferior bases widths of the chimney ((W_{e}/W_{g})), the ratio between the width of the chimney inferior basis and the absorber wall height ((W_{g}/H_{a})), and the ratio between the opening that connects chimney and room and the absorber wall height ((H_{i}/H_{a})). It is considered unsteady, incompressible, free convective, turbulent flows in a two-dimensional domain. The finite volume method is used to solve the time-averaged equations of continuity, momentum and conservation of energy. For closure of turbulence, it is employed the (k)-(varepsilon) model. Results showed that the best geometric configuration led to a mass flow rate 5.7 times superior than the worst configuration, showing the importance of solar chimney desing in this problem. Moreover, a strong sensibility of the investigated ratios on the mass flow rate was noticed.