Principle Of Heat Conduction Research Articles

Thermal transport of confined water molecules in quasi-one-dimensional nanotubes

Dimensions and molecular structures play pivotal roles in the principle of heat conduction. The dimensional characteristics of a solution within nanoscale systems depend on the degrees of confinement. However, the influence of such variations on heat transfer remains inadequately understood. Here, we perform quasi-one-dimensional non-equilibrium molecular dynamics simulations to calculate the thermal conductivity of water molecules confined in carbon nanotubes. The structure of water molecules is determined depending on the nanotube radius, forming a single-file, a single-layer, and a double-layer structure, corresponding to an increasing radius order. We reveal that the thermal conductivity of liquid water has a sublinear dependency on nanotube length exclusively when water molecules form a single file. A stronger confinement leads to behavioral and structural characteristics closely resembling a one-dimensional nature. Moreover, single-layer-structured water molecules exhibit enhanced thermal conductivity. We elucidate that this is due to the increase in the local water density and the absence of transitions to another layer, which typically occurs in systems with double-layer water structures within relatively large radius nanotubes.

Principle, Fabrication and Applications of Micro-Nano Fluid Dynamics

A new generation of efficient heat transfer and cooling technologies has been studied by researchers since the 1990s due to the rise of nanotechnology. In 1995, Professor S.U.S. The idea of 'nanofluids' was first proposed by Choi from the Aragon National Laboratory in the United States, which combines nanotechnology with traditional thermal engineering in an innovative way. Enhanced heat transfer is a field where nanofluid technology has broad application prospects and potential significant economic value, and is known as the 'future cooling and heat dissipation technology'. The theme of this article is the principles, preparation processes, and application fields of micro-nano fluids. The research on nanofluids still needs to be carried out. Due to their unique thermal conductivity properties, they can theoretically be widely used in fields such as industry, energy, aerospace, automobiles, air conditioning and refrigeration, electronics, etc. The aim of this study is to examine the heat conduction principle of nanofluids, the basic preparation process, and some applications of nanofluids in the field of enhanced heat conduction.

Processing Method of Soil Temperature Time Series and Its Application in Geothermal Heat Flow

Nowadays, geothermal resources have become one of the important means for mankind to solve global energy problems and environmental problems, and the exploration and development of geothermal resources are of great significance for sustainable development. However, in view of the complex geological background of the plateau region, the number of heat flow measurement points in this area is small or even blank, thus becoming an important factor limiting the exploration of geothermal resources in this region. In this article, a new model based on Fourier analysis and heat conduction principle is established to process and analyze the long-term monitoring data of soil temperature and eliminate the influence of temperature change on soil temperature as far as possible, so as to improve the calculation accuracy of soil conduction heat dissipation. The experimental results show that the fluctuation range of soil temperature at 20 cm before the correction was large, and the fluctuation range was 2.58°C–14.284°C, which was because the soil here was closer to the land surface and was affected too much by the temperature fluctuation, and as the soil depth deepened, the temperature fluctuation slowly became smaller, and the fluctuation range was 6.67°C–11.15°C at 50 cm, but the effect of temperature fluctuation was still obvious. Also, the fluctuation range was basically reduced within 0.3°C after temperature correction. In this method, the thermal diffusion coefficients of the soil at different depths can be obtained, and the calculated temperatures at the corresponding depths can also be obtained, which can be used to infer the approximate ground temperature gradient of the measured area. This study aims to develop a convenient and fast model for processing soil temperature time series and to provide technical support for developing geothermal resources in highland areas or assessing the geothermal potential of the region.

Thermoelectric generators

As the world is changing and developing with every passing day, the requirements of power are also increasing. There is a shift in utilizing the electrical energy as much as possible and for this reason, many countries have already made policies for completely ruling out the machines which don’t run on electricity. Apart from electricity, there are other forms of energy that can be used to convert that form into a more desirable form. For example, in a plant where the smoke comes out of the chimneys or in a car, the smoke carries a large amount of thermal energy with it. This energy is nothing but a waste and reduction in the efficiency of the systems. If somehow, this energy could be recovered, the efficiency can be increased. Thermoelectric generators serve for this purpose. Thermos electric generators get the heat and using the principle of heat conduction and p and n type materials, the heat can be directly converted into the electricity. There are many materials available in the market for p and n type but in our case, we chose silicon germanium which is also one of the most commonly used. First of all, a single module of thermoelectric generator will be made using p and n type material, as well as using conductive material and some ceramic substance. Then, the entire assembly will be made and this assembly will be exported to Ansys where custom materials will be added and applied on to the geometry. After performing analysis on full model, a comparative study will be presented in which the effect of material of conductive plate on to the voltage difference will be studied

Research on Thermal Characteristics of IGCT Based on Structure Function

According to the principle of heat conduction during the operation of semiconductor devices, a GCT package model of IGCT devices is established. Perform transient simulation and use structure function analysis software for analysis. Based on the thermal resistance and heat capacity curve obtained by the structure function analysis method, the factors that may affect the thermal characteristics of the device are analyzed from the two angles of the thickness of the molybdenum disk and the thickness of the copper cathode. Thermal analysis of the 1μm micro-gap on the surface of the molybdenum disk and suggestions for improvement were put forward. The research results show that the structure function method is a non-destructive analysis method that can obtain the thermal resistance and heat capacity of each layer inside the device with high accuracy. The application of this method can analyze the internal microstructure changes of the device, and provide convenience for the research and evaluation of the thermal characteristics of the device.

Study on Mechanism of Glass Molding Process for Fingerprint Lock Glass Plates

Curved glass is widely used in 3C industry, and the market demand is increasing gradually. Glass molding process (GMP) is a high-precision, high-efficiency 3D glass touch panel processing technology. In this study, the processing parameters of fingerprint lock glass panels were deeply analyzed. This paper first introduces the molding process of the glass panel, discusses the glass forming device, and explains the heat conduction principle of the glass. Firstly, it introduces the forming process of the glass panel, discusses the glass forming device, and explains the heat conduction principle of the glass. Secondly, the simulation model of a fingerprint lock glass plate was simulated by MSC. Marc software. The stress relaxation model and structure relaxation model are used in the model, and the heat transfer characteristics of glass mold are combined to accurately predict the forming process of glass components. The effects of molding temperature, heating rate, holding time, molding pressure, cooling rate and other process parameters on product quality characteristics (residual stress and shape deviation) were analyzed through simulation experiments. The results show that, in a certain range, the residual stress is inversely proportional to the bending temperature and heating rate, and is directly proportional to the cooling rate, while the shape deviation decreases with the increase of temperature and heating rate. When the cooling rate decreases, the shape deviation first decreases and then increases. Furthermore, a verification experiment is designed to verify the reliability of the simulation results by measuring and calculating the surface roughness of the formed products.

Research forecasting model to solve the problem of marketing needs of enterprises

This essay focuses on the temperature variation law of the center of the target board soldering area at a certain position when the reflow oven starts working as the core discussion. Using the principle of heat conduction, Fourier's law to solve the problem of temperature values and temperature change laws in the center of the soldering area of the target circuit board at different locations under set conditions. As in the actual process, the temperature change in the center of the soldering area is limited to certain conditions, we can use the target planning, prediction methods, to build a model to solve the maximum problem. At the same time we need to consider the quality of the target circuit board, the use of neural networks, genetic algorithms to establish optimization models for target optimization, and ultimately the optimal furnace temperature curve.

A domain of influence in the Moore–Gibson–Thompson theory of dipolar bodies

We establish a domain of influence theorem for the mixed initial-boundary value problem in the context of the Moore–Gibson–Thompson theory of thermoelasticity for dipolar bodies. Based on the data of the mixed problem, we define, for a finite time t>0, a bounded domain and prove that the displacements and the temperature decrease to zero, outside of the domain . The main result is obtained with the help of two auxiliary results, namely two integral inequalities. We managed to prove that this type of influence domain can be built even if it is considered in a much more complex context. Thus, compared to the classical context in which this concept appeared, we took into account the heat conduction principle from the Moore–Gibson–Thompson theory, we considered the thermal effect and we analyzed the effect of the dipolar structure of the environment.

Research on Heat Transfer of Multi-Media Protective Clothing Based on Unsteady State

At present, the problem of heat insulation thickness of heat-resistant clothing becomes more and more serious. To solve this problem, the steady-state heat conduction principle is used to solve the optimal value critical problem in unsteady heat conduction, and the feasibility is established. The critical equilibrium time physical quantity is created for approximate representation. System steady state time. Secondly, the steady-state thermal conduction thermal resistance circuit model is combined with the nonlinear programming model for solving the optimal solution. The proportional relationship between thickness and temperature difference and critical equilibrium time is used as the constraint condition to solve the optimal material thickness in different environments.

An interior space evacuation model based on heat conduction

To effectively solve the problem of interior space crowd evacuation safety, an evacuation cellular automaton model using a heat transmission approach is established. In this model, a probabilistic formula for pedestrian movement is first given. It is combined with both field and velocity saturation using the principle of heat conduction to explain pedestrian crowding, and an iterative evacuation algorithm is presented. Finally, evacuation experiments are performed using real scenes. Key factors, such as travel distance and degree of crowding, that influence the evacuation efficiency are further studied using the established simulation experimental platform. The results show that the method has good adaptability.

The least action principle for heat conduction and its optimization application

The least action principle is used in various disciplines including linear transport processes. However, non-equilibrium thermodynamic analyses of linear transport processes involve the dot product of the thermodynamic flux and the thermodynamic force which must be the entropy production rate in the linear phenomenological law for such processes; thus, Fourier’s heat conduction law cannot be derived based on the variation of the entropy production rate. A generalized linear phenomenological law for various types of linear transport processes, including heat conduction, mass diffusion, electric conduction and fluid flow in porous medium is introduced here where the dot product of a generalized flux and a generalized force is taken as the action to give the generalized linear phenomenological law. For heat conduction, the entransy dissipation rate, which is the dot product of the heat flux and the negative of the temperature gradient, is taken as the action, and the variation of the entransy dissipation rate then leads to Fourier’s heat conduction law with constant thermal conductivity. Hence, the action of heat conduction process is the entransy dissipation rate rather than the entropy production rate. A nonlinear constitutive relation for the heat conduction with temperature dependent thermal conductivity is then converted to a linear problem by introducing a generalized temperature, which gives a least generalized entransy dissipation principle for nonlinear heat conduction processes. Finally, the least entransy dissipation principle is applied to optimize a one-dimensional heat conduction problem without heat-work conversion as an example where the minimum entropy generation principle is not applicable.

Thermal Conductivity and Specific Heat Capacity of Different Compositions of Yttria Stabilized Zirconia-Nickel Mixtures

Ceramic-metal composites also known as functionally gradient materials (FGM) are composite materials which are fabricated in order to have a gradual variation of constituent materials’ thermal and mechanical properties so as to have a smooth variation of the material properties in order to improve the overall performance and reduce the thermal expansion mismatch between ceramic and metal. The objective of the study is to determine the thermal properties of various percentage composition of Yttria stabilized zirconia-Nickel mixtures for application as thermal barrier coating materials in automotive turbocharger turbine volute casing. Specific heat capacity of different percentage composition of ceramic-metal powder composite were determined using DSC822 differential scanning calorimeter (Mettle Tolodo, Switzerland) at temperature ranges between 303K to 873K. While the thermal conductivity of the different percentage composition of ceramic-metal composite structures were determined using P5687 Cussons thermal conductivity apparatus (Manchester, UK) which uses one-dimensional steady-state heat conduction principle. The results have indicated that the specific heat capacity of the FGM increases sharply with an increase in temperature while the thermal conductivity of the FGM decreases with an increase in temperature. These results strongly agree with the theoretical and experimental values as well as the rule of mixtures obtainable in literature, which indicated the suitability of these FGM materials for thermal barrier coating applications.

基于热传导原理电枢平均磨损率计算

基于热传导原理电枢平均磨损率计算

A short remark on He-Lee’s variational principle for heat conduction

Tao and Chen claimed that they obtained a new constrained variational principle for heat conduction (Tao, Z. L., Chen, G. H., Thermal Science, 17 (2013), 3, pp. 951-952), however, this short note concludes that it is not new at all. It is equivalent to He-Lee 2009 variational principle.

Remark on a constrained variational principle for heat conduction

The heat conduction equation is re-studied by the semi-inverse method combined with separation of variables; a new variational principle for the heat conduction equation is obtained. Equivalence of the existed two in literature is shown. The significance of variable separation is confirmed once more.

Variational principles in terms of entransy for heat transfer

A variational principle for heat conduction is formulated which results in the steady state heat conduction equation established from the Fourier law. Furthermore based on the thermodynamics in terms of entransy a more general functional is defined for incompressible fluids. We show that extremizing this functional gives rise to the state described by the Navier-Stokes-Fourier equations with vanishing substantive derivatives of the temperature and velocity field. In this sense one may conclude that this variational principle is consistent with the Navier-Stokes-Fourier equations. Therefore the variational principle developed in the present work demonstrates a great advantage over the minimum entropy production principle.

Influence of Reinforcement on Temperature and Stress of Hollow Pier

This paper put circular hollow bridge pier under cold wave as an example. Based on solid heat conduction principle, we selected its border and initialized condition according with actual circumstance. Combining solid heat conduction differential equation and generalized hooke’s law which takes temperature stress into account, we have calculated the temperature and stress of concrete piers with different reinforcement ratio by ANSYS finite element software. These results indicate that the longitudinal bars and horizontal ring stirrups in concrete circular hollow pier under cold wave will increase its outer surface temperature tensile stress. Namely the reinforcements in concrete circular hollow pier not only do not prevent its outer surface cracks under the action of cold wave, but will also promote the surface cracks to produce faster. Therein, the contribution of horizontal ring stirrups to the surface cracks is greater than the longitudinal bars.

Thermal–Mechanical-Based Soft Tissue Deformation for Surgery Simulation

Soft tissue deformation is of great importance to virtual reality-based surgery simulation. This paper presents a new methodology for the modeling of soft tissue deformation. This methodology converts soft tissue deformation into thermal–mechanical interaction according to the continuum mixture theory of soft tissues, and thus heat conduction of mechanical load and non-rigid mechanics of motion are combined to govern the dynamics of soft tissue deformation. The mechanical load applied to a soft tissue to cause a deformation is distributed among mass points of the soft tissue according to the principle of heat conduction. A thermal–mechanical model and associated model construction algorithms are developed to describe the distribution of the mechanical load in the tissue. A heat flux-based method is established for derivation of internal forces from the distribution of the mechanical load. Real-time interactive deformation of virtual human organs with force feedback has been achieved by the proposed methodology for surgery simulation. The proposed methodology not only accommodates isotropic, anisotropic and inhomogeneous materials by simply modifying thermal conductivity constants, but it also accepts local and large-range deformation.

A constrained variational principle for heat conduction

The heat equation is re-studied in this Letter in view of variational theory. By the semi-inverse method, a variational principle for the heat conduction is obtained, which is first appeared in the literature. The physical understanding of the obtained variational principle still needs further explanation.

Development of an isothermal heat-conduction photocalorimeter

Assessing photostability (particularly of pharmaceuticals) is of growing importance, but hampered by a lack of reliable, rapid experimental testing protocols and instrumentation. In particular, most approaches require irradiation of the sample separately from the analytical measurement, which increases both experimental complexity and the number of assumptions that must be made when calculating stability. One technique that may obviate this is photocalorimetry, principally because the reporter of change (heat) is measured directly as a sample is irradiated. Although not a new idea, the design challenges of photocalorimeters are complex, primarily because light power is being introduced to the calorimeter which can thus both saturate the amplifiers and swamp the response of the sample. Careful instrument design is thus paramount. The aim of this work was to develop a robust, compact, and easy to use photocalorimeter with the immediate focus of developing photostability assays for pharmaceuticals. The final instrument design, arrived at through a series of iterative design modifications, is based on a twin differential heat-conduction principle and achieves an average base line deflection of -0.04+/-0.11 microW with light irradiating the sample cell. The performance capabilities of the instrument were demonstrated using a model system; the photodegradation of 2-nitrobenzaldehyde in solution.