Heat Transfer Law Research Articles

Heat transfer effect on the performance of thermal Brownian heat engine

A new finite time thermodynamic model of thermal Brownian heat engine is established. The heat transfer between heat reservoir and viscous medium is considered and is assumed to be obeyed Newton’s heat transfer law. The effects of heat transfer process on system performance are studied in detail. The key performance parameters of system are derived. For the fixed temperature of reservoirs, the temperatures of viscous medium are optimized for maximizing the power. For a fixed total heat exchanger inventory, the distribution of heat exchanger inventory is also optimized for maximizing the power. The effects of key parameters on the performance of the system are investigated, and the optimal operating region is given. The results show that the thermodynamic performance of system can be improved by enhancing the heat transfer between reservoir and heat engine. There exist optimal distribution of heat exchanger inventory and optimal temperatures of viscous medium corresponding to the maximum power, respectively. There also exists a pair of barrier height and external load corresponding to double maximum power. The efficiency decreases versus barrier height and increases versus external load. The asymmetry potential is relevant to the heat flow caused by overcoming external load of particles. The efficiency is irrelevant to the working temperature, and it only depends on the internal parameters of heat engine.

Characterization and Finite Element Modeling for Thermoset Resin of Carbon Fiber Prepregs During Curing

Abstract In this study, an epoxy resin, YZ-05, designed specifically for carbon fiber reinforced polymer prepregs, was characterized and modeled. A degassing method for the highly viscous YZ-05 was established for specimen preparation. To numerically model the behavior of YZ-05 in curing, several components, including the heat transfer, curing kinetics, and viscoelastic constitutive law ones, were developed, and the corresponding material properties to be input were tested. As YZ-05 shows severe creep at high temperature under mechanical loading, the combination of digital image correlation (DIC) and thermography technique was utilized to obtain its thermal expansion and chemical shrinkage. In the aspects of viscoelastic behavior, stress relaxation tests were performed based on time–temperature superposition principle with a numerical method to calculate shift factors. After development and input identification, these modeling components for YZ-05 resin were integrated and the modeling results were validated using experiments, where bending of resin beams was induced during curing.

Optimal piston motion configuration for irreversible Otto cycle heat engine with maximum ecological function objective

Applying optimal control theory and finite time thermodynamics, a practical Otto cycle heat engine with friction, pressure drop and heat transfer losses is studied. The maximum ecological function is taken as optimization objective, and the optimal piston motion configuration of the Otto cycle is obtained with the Newton’s heat transfer law between the working fluid and the environment. The fuel consumption and the total cycle time are fixed in the optimization. The optimal piston motion laws corresponding to the maximum ecological function configuration when the piston motion accelerations are unconstrained and constrained are obtained, respectively. By numerical examples, the piston motion optimal configurations under different optimization objectives and heat transfer laws are compared.

Experimental Study on Support Vector Machine-Based Early Detection for Sensor Faults and Operator-Based Robust Fault Tolerant Control

Considering sensor faults for a thermoelectric cooler actuated by Peltier devices, this work proposes an operator-based robust nonlinear fault tolerant controller (FTC) integrated with early fault detection using a support vector machine (SVM). Firstly, a physical model is formulated based on the law of heat transfer, and the estimated model is derived based on Volterra identification. Then, an operator-based robust nonlinear control system is employed to compensate for uncertainties and to eliminate the effects of coupling. Furthermore, FTC integrated with SVM-based early fault detection is designed to improve the safety performance in the case of sensor faults. The simulation results indicate that SVM-based fault detection can shorten the detection time in comparison to the conventional method without the SVM classier. The experiment results are utilized to verify the tracking performance of the proposed FTC method in the case study.

Effective thermal conductivity of loose residual coal in goaf: Comparative analysis of experiment and model

The effective thermal conductivity (ETC) model of loose residual coal in goaf is a method to study the heat transfer law of spontaneous combustion in goaf. In order to study the effect of coal particle size and ambient temperature on heat transfer, coal samples of different sizes were taken from the FuSheng (FS) mine, and the void fraction, the thermal conductivity (TC) of the residual coal under different ambient temperature were tested. Additionally, four types of ETC models of loose residual coal in goaf were obtained and the average relative errors of the TC were analyzed. The results showed that the void fraction, the coal particle size and ambient temperature have different effects on the spontaneous combustion of the residual coal. The effect of coal sample size on the heat transfer is 100 times that of the ambient temperature. The changes in the ETC and average relative error of the different models were consistent. The heat transfer in the spontaneous combustion of residual coal has a direct relationship with the spatial distribution and heat transfer modes of the loose residual coal in the goaf.

Low Mach number limit of the full compressible mhd equations with Cattaneo’s heat transfer law

Low Mach number limit of the full compressible mhd equations with Cattaneo’s heat transfer law

Development of a Method for Estimating Thermal Conductivity of Organic Deposits on the Wax Flow Loop Laboratory Installation

During the oil production, the occurrence of such a complication as the formation of wax deposits is not uncommon. The fight against these deposits, as well as the development of modern methods of dealing with them, is one of the most important tasks of the subsoil user. Many modern methods of modeling deposits require the exact determination of such a quantity as the thermal conductivity of organic deposits. Based on the analysis of scientific literature, it can be concluded that there is no method developed for estimating this value under conditions of wax formation without affecting their pore structure. The paper describes a method for determining this value based on the results of a study of the process of formation of organic deposits on the laboratory installation "Wax Flow Loop" based on the laws of heat and mass transfer. Based on the results of applying this technique, it becomes possible to determine the thermal conductivity of organic deposits, the value of which correlates with the values given in the reference and scientific literature. In addition, the presence of a correlation between the value of the thermal conductivity of deposits and the component composition of the studied fluid was determined. The application of the described technique will make it possible to most accurately simulate the processes of oil production and determine the technological effectiveness of the use of modern methods of combating organic deposits.

Unsteady flow of Casson nanofluid through generalized Fourier's and Fick's law for heat and mass transfer

The purpose of this paper to explain the role and importance of fractional derivatives for mass and heat transfer in Casson nanofluids including clay nanoparticles. These particles can be found in water, kerosene, and engine oil. The physical flow phenomena are illustrated using PDE and thermophysical nanoparticle properties, and this paper addresses the Casson fractional fluid along with chemical reaction and heat generation. The heat and mass fluxes are generalized using the constant proportional Caputo fractional derivative. The present flow model are solved semi-analytically using the Laplace transform. We generated several graphs to understand how various flow factors affect velocity. The acquired results reveal that fractional parameters have dual behavior in velocity profiles. Velocity and temperature are also compared to previous studies. Compared to the other fractional derivatives results, field variables and proposed hybrid fractional derivatives showed a more decaying trend. Furthermore, significant results of clay nanoparticles with various base fluids have been obtained.

EXPERIMENTAL ASSESSMENT OF THE SIMILARITY LAWS FOR TWO-DIMENSIONAL NONLINEAR HEAT TRANSFER IN BUILDING MATERIAL

EXPERIMENTAL ASSESSMENT OF THE SIMILARITY LAWS FOR TWO-DIMENSIONAL NONLINEAR HEAT TRANSFER IN BUILDING MATERIAL

Study of the Convective Heat Transfer Law and Temperature Prediction of the Duct in High-Temperature Tunnels

Study of the Convective Heat Transfer Law and Temperature Prediction of the Duct in High-Temperature Tunnels

On the shape factor in iceberg deterioration by forced convection

The present paper concerns the conventional use, in offshore ice engineering, of the convective heat transfer equation presented by White, et al. (1980) for iceberg keel degradation due to forced convection. The equation describing loss of iceberg keel mass involves a shape factor which depends on both the actual shape of the keel and on the governing convective heat transfer law applicable across the boundary layer over the keel. Two shape factor values from White et al. (1980) depend on a binary overall shape classification: tabular and non-tabular icebergs. Since the relative mass loss varies linearly with the shape factor, any uncertainty in it propagates directly into the mass loss model. The formulation proposed in White et al. (1980) is justified for very wide icebergs in a flow which can be presented as two-dimensional. However, it is not clear whether all arbitrary icebergs in arbitrary flow may be represented by the same shape factor values and how the shape factor over an ensemble of tabular or non-tabular icebergs would vary. The present work provides further insight into the quantification of the shape factor. For this, the model provided in White et al. (1980) is applied to several analytical geometrical shapes in either two-dimensional flow or three-dimensional axisymmetric flow. The iceberg keel is presented either by half of a cylinder with elliptic cross-section or by half of a spheroid, i.e., a body of revolution. The shape factor values for the analytical shapes have been found to be around 12%–20% lower than the shape factors given in White et al. (1980). The values reported here for the elliptic deep half-cylinder can be used as conservative limit for engineering estimations of the iceberg deterioration rate due to forced convection.

РАСЧЁТНЫЙ МОДУЛЬ ДЛЯ ОПРЕДЕЛЕНИЯ ФИЗИЧЕСКИХ ПАРАМЕТРОВ В КАНАЛЕ РЕАКТОРА С ТЕПЛОНОСИТЕЛЕМ ЗАКРИТИЧЕСКОГО ДАВЛЕНИЯ

The paper describes the software module FRC-SCP intended for thermohydraulic simulation of a coolant under supercritical pressure (SCP) and a cooled fuel rod. Several designs of supercritical water reactors utilize the transition of the coolant from the pseudoliquid state to pseudogas while it is heated in the reactor core. SCP coolant under pseudophase transition exhibits specific behavior as its density changes significantly. Furthermore, coolant thermophysical properties (density, heat capacity, viscosity, thermal conductivity) can also vary across the coolant channel affecting heat transfer from the fuel rod to the coolant and consequently the fuel temperature. Existing feedback dependencies on coolant density and fuel temperature are important for the nuclear safety analysis of the reactor. The paper considers the present version of the FRC-SCP module. It implements the steady-state thermohydraulic channel solver to calculate coolant parameters: temperatures of the flow core and a heater, as well as coolant pressures, densities etc. User-specified correlations define the heat transfer law under the normal conditions. The module solves the thermal problem for the fuel rod consistently with the channel thermohydraulic problem. It is also possible to couple the FRC-SCP module with the neutron physical codes. Thermohydraulic module is tested against experiments on the heat transfer to SCP water in heated tubes. We discuss the behavior of the fuel cladding under conditions imitating the deteriorated heat transfer modes and the effect of the nuclear fuel thermal conductivity.

Variance-based global sensitivity analysis of a hybrid thermoelectric generator fuzzy system

In this paper, Hybrid thermoelectric generators (HTEG) model was established based on nonequilibrium thermodynamics and Newton's heat transfer law. Fuzzy theory was used to describe the decision-making and cognitive uncertainty of HTEG design variables in working environment and material. The influence of the fluctuation of design parameters on the output performance is studied using a variance-based global sensitivity analysis. Taking a sampling sample N = 10,000, the main and total Global sensitivity indices of design parameters are calculated, and the sensitivity ranking are obtained. In addition, the analysis was applied to contact effects and the number of serial and parallel components on the sensitivity of the output to the uncertainty of the design variables. The results show: the heat and cold source temperature, load resistance and Seebeck coefficient had a greater impact on the output power and the impact on the conversion efficiency mainly came from the heat and cold source temperature, load resistance and thermal resistance of the thermoelectric module. The contact effects and the number of thermoelectric components connected in series and parallel exerted a certain influence on the uncertainty of output response. The results can be used to guide the performance analysis and parameter optimization of HTEG in application.

Procedure for calculation of the admissible continuous power transmission currents of overhead wires and contact lines

The proposed methodology summarizes published and original domestic and foreign theoretical and experimental materials on heating and cooling of spiral and shaped wires of overhead power transmission lines and electric power systems and uses those of them that best meet the fundamental laws of heat transfer. Formulas for calculating the surface area for spiral and shaped wires are given. A generalized formula for the convective heat transfer coefficient taking into account the direction and speed of the wind, including for the anti-ice regime, is given. The parameters of this formula do not coincide with the existing ones, since they are based on the experimental data for spiral and shaped wires, and not for round pipes. The formula for calculating the power of heat transfer under solar radiation is given. A generalized formula is given for calculating the continuous allowable current, all components of which are described in detail in the article.

Investigation about basic heat transfer law in the micro pulse tube

Pulse tube is one of the main parts of the pulse tube cryocooler. Ideally, the pulse tube works under adiabatic environment without heat transfer loss. But in real case, entropy is generated in the pulse tube itself from heat exchanged with the walls, turbulent mixing of the hot and cold gas segments, circulation of the gas within the tube, and end effect losses from the adiabatic to isothermal transition in the cycle. All these processes reduce the enthalpy flow in the pulse tube from the ideal acoustic power. However, no 1D model can sufficiently simulate these effects in the past. Also, most of the 1D models about the pulse tube part with a heat transfer coefficient is far from accurate, especially for micro pulse tube in which the heat transfer is more obvious. This work revealed that the basic heat transfer changes instantaneously and shows different tendencies in different time of one cycle, and no suitable law or explanation could fare well the phenomenon eventually. The phase angle changes from negative to positive that results in the relatively heat flux along the pulse tube becomes smaller, that could help the pulse tube to make a good performance.

Justification of mathematical models of variable heat supply during grain drying

The article presents the results of studies of the efficiency of drying grain by reducing the specific energy consumption, allowing improving the quality of the resulting products and in-creasing the productivity of drying. The achievement of the results was a mathematical model, which was based on the general laws of heat and mass transfer, reflecting the specific features of the research. It is not that most continuous dryers for bulk materials have several zones with different parameters of the input and output-drying substance, which carry out drying under variable dynamic conditions.

Computer Intelligent Numerical Simulation of TIG Welding Using Platy Tungsten Electrode

In order to reveal the law of arc plasma flow and heat transfer in the process of flat tungsten electrode TIG welding as auxiliary heat source for hardfacing of cast iron surface. According to the free burning TIG arc using platy tungsten electrode, A three dimensional (3D) model for tungsten inert gas welding using platy tungsten electrode has been developed. The whole region of platy tungsten TIG arc, namely, platy tungsten cathode, arc plasma and anode surface is treated in a unified numerical model. By using fluent software to do the second development of equations source and solve these equations, the distribution of temperature, velocity and current density are obtained. The simulation results show that the current of flat tungsten electrode is more dispersed, and the heat generation of arc is more dispersed, which leads to the decrease of arc temperature; The current density on the cathode is much higher than that on the anode.

Research on Key Technologies for Improving the Electro catalytic Performance and Physical Properties of Lithium Batteries in Electric Vehicles

Aiming at the uneven heat generation in various parts of the electric vehicle lithium battery pack during the discharge process, the heat generation mechanism is studied, and the lithium battery catalytic performance model is established to obtain the current density and heat generation rate distribution law of the lithium battery cell on the cell. The thermal model can simulate the thermal behavior of the battery under application conditions. Study the laws of battery heat production, heat transfer, and heat dissipation, and calculate the temperature changes inside and on the battery and the temperature field information in real time to provide a basis for the design and optimization of the battery and battery pack thermal management system. The simulation results show that the established model can predict the heating distribution and temperature field of the internal layered structure of the lithium-ion battery, which is helpful for the subsequent analysis of key influencing factors.

Research on Server Installation Direction Based on Newton's Heat Transfer Law

Nowadays, the storage of Seabed Data Center has become a new data storage technology, which has attracted much attention all over the world. Firstly, through the study of Newton's heat transfer law, it is analyzed that the premise of heat dissipation is the temperature difference inside and outside the solid container. On the basis of meeting this condition, the maximum installable quantity caused by the different arrangement of different servers in the container is calculated. The results show that when the server is placed in a horizontal form inside the container, the maximum number of 330 servers of the same type can be placed at the same time, while when it is placed in a vertical manner, the number of servers is only 269. From the comparison of the above conclusions, it can be seen that the horizontal installation method is more suitable for the internal heat dissipation of the server.

Determination of temperature distribution on windings of oil transformer based on the laws of heat transfer

Object of research: development of a technology for determining the temperature of the winding of a power oil transformer, in particular, the analysis of thermal processes in the winding of a power transformer during short-term overloads, taking into account the influence of the environment.
 Investigated problem: temperature distribution in the winding of a power oil transformer taking into account short-term load surges in the problem of assessing the residual life of the insulation of the transformer winding by temperature aging. The calculation of the temperature distribution in the winding was carried out using the passport data and characteristics of the power oil transformer, including the winding, transformer oil, load currents.
 Main scientific results: a mathematical model was calculated, with the help of which the results of temperature distribution in the transformer winding were obtained during short-term load surges or constant work with an increased load. According to the presented model, the analysis of the cooling time of the transformer winding after short-term overloads is carried out. Comparing the results obtained on the simulation model with the known results of experimental studies of the temperature distribution in the winding of a power transformer, the adequacy of the mathematical model is proved. It is shown that the use of the laws of heat transfer in a homogeneous plate to analyze the temperature distribution in the transformer winding is not wrong, but requires clarifications and simplifications.
 The area of practical use of the research results: enterprises of the machine-building industry and energy companies specializing in the production and operation of transformer equipment. Innovative technological product: simulation model of heat distribution in a transformer winding, which can take into account the load of the transformer, the effect of the environment on the insulation of the transformer windings.
 An innovative technological product: a method for diagnosing the duration of the non-failure operation of a transformer, which makes it possible to ensure trouble-free operation and save money for the repair of transformer equipment.
 Scope of application of the innovative technological product: design and development of diagnostic systems for windings of power oil transformers