Heat Conduction In Bodies Research Articles

Study of Transversely Isotropic Visco-Beam with Memory-Dependent Derivative

Based on the modified Moore–Gibson–Thompson (MGT) model, transversely isotropic visco-thermoelastic material is investigated for frequency shift and thermoelastic damping. The Green–Naghdi (GN) III theory of thermoelasticity with two temperatures is used to express the equations that govern heat conduction in deformable bodies based on the difference between conductive and dynamic temperature acceleration. A mathematical model for a simply supported scale beam is formed in a closed form using Euler Bernoulli (EB) beam theory. We have figured out the lateral deflection, conductive temperature, frequency shift, and thermoelastic damping. To calculate the numerical values of various physical quantities, a MATLAB program has been developed. Graphical representations of the memory-dependent derivative’s influence have been made.

Numerical modeling of heat conduction in bodies with cracks

All structural materials contain certain microdefects. Various elements of aircraft and spacecraft made from these materials are subjected to high mechanical loads and thermal effects during operation, which, in turn, can lead to the evolution of defects and total fracture of individual parts of the mechanism. Therefore, a quantitative and qualitative estimation of the stress and temperature fields in different bodies with complex configuration of external loading and temperature disturbances is needed. This paper presents a technique for numerical modeling of the temperature field in a medium weakened by a large system of partially heat penetrable cracks, including the possibility of considering it as an infinite periodic system. The method is based on a numerical algorithm, which uses the expansion of the solution into a finite series. Every term of this series is a certain analytical solution of the heat conduction theory obtained by the authors. To verify the method, the numerical results were compared with the well-known analytical solutions both for a configuration with finite number of cracks and for the periodic system. Also the heat flux intensity factors for a doubly periodic system were determined.

Inclusion of unsteady heat conduction in regular bodies subject to uniform surface heat flux in a heat transfer course

The present study is concerned with the analysis of unsteady heat conduction in regular bodies (large plane wall, long cylinder, and sphere) with constant initial temperature, prescribed surface heat flux and thermal properties of the solid that are invariant with temperature. Surprisingly, this important topic is absent in textbooks on heat transfer. The exact evaluation of the dimensionless surface temperatures varying with the dimensionless time in the regular bodies over the entire dimensionless time domain [Formula: see text] is carried out with a symbolic algebra code. Thereafter, regression analysis is applied to the data gathered for the dimensionless surface temperatures varying with the dimensionless time of the regular bodies inside the dimensionless “small time” time sub-domains [Formula: see text]. The dimensionless threshold time [Formula: see text] is a decisive parameter that establishes the borderline between the “small time” sub-domain [Formula: see text] and the “large time” sub-domain [Formula: see text] comprising the entire dimensionless time domain [Formula: see text]. Based on regression analysis, compact asymptotes are constructed for the dimensionless surface temperatures varying with the dimensionless time inside the dimensionless “small time” sub-domain [Formula: see text]. At the end, agreements with the dimensionless exact, analytical surface temperature distributions (the baseline solutions) valid for the dimensionless time sub-domain [Formula: see text]. are considered of excellent quality.

Why only a man turned out to be the owner of mind?

It is considered that the main distinguishing feature of Homo sapiens from other living beings is the presence of his mind. There are many hypotheses regarding the origin of the human mind. The complexity of the problem lies in the fact that it is impossible to experimentally test any of the existing hypotheses. Perhaps we will never fully know how the human mind arose, but it is necessary to strive for this. Here we discuss the possible causes of the origin of a large brain in modern man, implying that the mind is ultimately a product of the human brain. We believe that in order for such a large brain to arise, profound and possibly unique changes in the genome and in the human body had to occur, which did not take place in other higher primates. The role of the evolution of the karyotype and heterochromatin part of the genome in the immediate ancestors of Homo s. sapiens, which led to an increase in the level of heat conductivity of their bodies changed the existing mechanisms of thermoregulation and led to the appearance of hairless skin, which, together, led to a sharp increase in the size of the brain, with the ensuing consequences, is discussed. We believe that the increase of the human brain size was not the result of drastically changes of the structural genes. Most likely it was the consequence of more ordinary events, such as evolution of karyotype, constitutive heterochromatin in chromosomes, human body heat conductivity, skin and thermoregulation. An experimental test is proposed to test the hypothesis put forward.

Objective equations of heat conduction in deformable bodies

The paper is devoted to the modeling of heat conduction in deformable media. The constitutive functions are in the form of rate equations which generalize the Maxwell–Cattaneo law. The purpose is to establish equations compatible with a finite speed, thermodynamically consistent, and objective. Both Lagrangian and Eulerian versions of the models are investigated. It follows that the time derivative of the Lagrangian description is associated with the Truesdell derivative of the Eulerian description. In a generic rate equation in the Eulerian description the stress turns out to be affected by the heat flux. The stress is unaffected if the derivative is the corotational one. Next, in accordance with recent literature, a time fractional derivative is also considered for the rate equation. As to wave propagation of jump discontinuities it follows that the time-fractional derivative is continuous even for discontinuities of the time derivative thus maintaining the paradox of infinite speed of propagation.

The Role of Human Skin Color and Body Heat Conductivity in Adaptation to Hot and Cold Climates

As is known Homo s. sapiens is the only living creature that has managed to inhabit the whole of the Earth, while remaining a single tropical biological species. The case is really unique considering that all this happened in an unprecedentedly short (by evolutionary scale) period of time, if the beginning of this process is considered to be its exit outside of East Africa about 30 000 - 50 000 years ago. However, science does not know everything about how all this happened to a species that itself emerged relatively recently (130 000 - 200 000 year ago) and nevertheless managed to do what other species failed to do. One of the important questions that arises when comprehending this phenomenon is reduced to the following: what features of a human him to make such an unprecedented breakthrough in the settlement of the planet? In particular, what biological advantages or prerequisites did the ancestors of modern man possess when they decided to leave Africa? Usually, such advantages include its large neocortex with a high-functioning mind, high physiological plasticity, perfect system of physiological thermoregulation, the structural features of the upper limbs, unique sexual and reproductive behavior, etc., etc. Without disputing the importance of these well-studied advantages, we would like to add to this list two more that could play an important role in the settlement of all climatogeographic zones of Africa and Eurasia by man: variability of the skin color and the level of heat conductivity of his body. We believe that the skin color and the heat-conducting ability of the human body are involved in his adaptation to heat and cold climates through thermoregulation systems. After all, the skin is the largest human organ that is in direct contact with the ambient temperature.

Use of a Simple Homemade Apparatus to Teach Basic Thermal Concepts – Six Qualitative Demonstrations/Experiments

Understanding thermal concepts constitutes one of the most important challenges in teaching science as these concepts are central to the principals of science and allow students to build connections among scientific disciplines. From an early age, students’ interaction with daily phenomena and real situations comes to shape their conceptions of thermal concepts, which continues to guide them throughout their education. Conceptions that are sometimes different from the scientific norm. This article presents six qualitative experiments/demonstrations using a low-cost, easy to make apparatus that introduces students to thermal concepts such as heat conduction in solid bodies and thermal expansion. These are appropriate for high school or college students enrolled in non-major science courses (e.g., departments of primary education) and can easily be performed by elementary or middle school students, but care must be taken when dealing with tealight candle flames.

Analytical Solutions of Heat Conduction Problems for Anisotropic Solid Body

Exact analytical solutions of heat conduction problems in anisotropic twodimensional solid bodies are presented in this study. Timedependent and steadystate problems are considered. A linear coordinate transformation is introduced which reduces the anisotropic heat conduction problem to an equivalent isotropic one. The solution of the anisotropic heat conduction problem is expressed in terms of solutions of the corresponding isotropic heat conduction problem. The connection of data of the applied linear coordinate transformation and the thermal material properties of anisotropic solid body is analysed. All result of the paper is based on the Fourier’s theory of heat conduction in solid bodies. Examples illustrate the applications of the developed method

A steady-state heat conduction problem of a nonhomogeneous conical body

Numerous studies and textbooks deal with the steady-state thermal conduction of radially nonhomogeneous circular cylinder. In contrast, there are relatively few studies on the thermal conduction problems of conical solid bodies. This study is intended as a modest contribution to the solution of thermal conductance problems of nonhomogeneous conical bodies. A one-dimensional steady-state heat conduction in nonhomogeneous conical body is considered. The thermal conductivity of the hollow conical body in a suitable chosen spherical coordinate system depends on the polar angle but is independent of the radial coordinate and azimuthal angle coordinate. A functionally graded type of material inhomogeneity is considered. All results of the paper are based on Fourier’s theory of heat conduction in solid bodies.

Exact Analytical Solutions for a Nonstationary Linear Inverse Problem of Heat Conduction for Bodies of One-Dimensional Geometry with Boundary Conditions on One Surface, as Well as on Two Surfaces for a Plane Body, a Cold Cylinder and a Hollow Sphere, Obtained in a Closed Recurrent Form

Exact Analytical Solutions for a Nonstationary Linear Inverse Problem of Heat Conduction for Bodies of One-Dimensional Geometry with Boundary Conditions on One Surface, as Well as on Two Surfaces for a Plane Body, a Cold Cylinder and a Hollow Sphere, Obtained in a Closed Recurrent Form

Exact Analytical Solutions for a Nonstationary Linear Inverse Problem of Heat Conduction for Bodies of One-Dimensional Geometry with Boundary Conditions on One Surface, as Well as on Two Surfaces for a Plane Body, a Cold Cylinder and a Hollow Sphere, Obtained in a Closed Recurrent Form

Exact Analytical Solutions for a Nonstationary Linear Inverse Problem of Heat Conduction for Bodies of One-Dimensional Geometry with Boundary Conditions on One Surface, as Well as on Two Surfaces for a Plane Body, a Cold Cylinder and a Hollow Sphere, Obtained in a Closed Recurrent Form

On the characterization and stability of plane waves under hyperbolic two-temperature generalized thermoelasticity

The propagation and stability (Whitham’s criteria) of harmonic plane waves are described in the context of the hyperbolic two-temperature generalized thermoelasticity in which heat conduction in deformable bodies depends upon the difference between the double derivative of conductive and dynamic temperature. The exact dispersion relation solutions for the longitudinal plane wave are derived analytically. Several characterizations of the wave field, like phase velocity, specific loss, penetration depth, amplitude coefficient factor, and phase shift are examined for the low as well as high frequency asymptotic expansions. For the validity of analytical findings and to study the effect of varying hyperbolic two-temperature parameter on different characterizations, the numerical computation of a particular example is illustrated and displayed graphically. The results of some earlier works have been deduced and discussed from the present investigation as speciallimiting cases.

Thermoelastic interactions on hyperbolic two-temperature generalized thermoelasticity in an infinite medium with a cylindrical cavity

The thermoelastic interactions in an infinite elastic medium with a cylindrical cavity are described in the context of the hyperbolic two-temperature generalized thermoelasticity theory (recently proposed by Youssef and El-Bary, 2018) in which heat conduction in deformable bodies depends upon the difference between the acceleration of conductive temperature and the acceleration of dynamic temperature. The boundary of the cavity is assumed to be stress-free and is subjected to a thermal shock. The problem is formulated to compare between classical generalized thermoelastic model and hyperbolic two-temperature thermoelastic model, on the basis of Lord-Shulman model and hyperbolic two-temperature Lord-Shulman model in a unified way. The Laplace transform method and decoupling of the coupled differential equations are used to solve the problem. Explicit expressions for displacement, stresses and temperature fields are approximated for small-time. Numerical values are displayed graphically for different models and comparison is presented for the illustration of the problem.

Computation of spatio-temporal temperatures in simple bodies with thermal radiation cooling by means of the numerical method of lines (NMOL)

Abstract The objective of the present study is to examine an approximate numerical solution of unsteady heat conduction in simple bodies (wall, cylinder and sphere) with thermal radiation cooling to a nearby sink environment. The finite difference method to be employed is the N umerical M ethod O f L ines (NMOL), instead of the traditional finite difference methods. One component of NMOL discretizes the spatial derivatives of first and second order in the one–dimensional heat conduction equation using two-point and three-point central finite-difference approximations; both involve truncation errors of second order. This step generates an adjoint system of n ordinary differential equations of first order, which consists in n−1 ordinary differential equations of first order at the interior lines and one nonlinear ordinary differential equation of first order at the surface line. Another component of NMOL deals with the numerical solution of the adjoint system of n ordinary differential equations of first order along with the initial condition with the potent fourth order Runge-Kutta algorithm. The two controlling parameters are the radiation-conduction parameter NRC and the dimensionless sink temperature ϕs. The numerically-computed temperature distributions are channeled through the center, surface and mean temperature distributions for suitable combinations of NRC and ϕs.

The Numerical Method of Lines facilitates the instruction of unsteady heat conduction in simple solid bodies with convective surfaces

The present study on engineering education addresses the Method of Lines and its variant the Numerical Method of Lines as a reliable avenue for the numerical analysis of one-dimensional unsteady heat conduction in walls, cylinders, and spheres involving surface convection interaction with a nearby fluid. The Method of Lines transforms the one-dimensional unsteady heat conduction equation in the spatial and time variables x, t into an adjoint system of first-order ordinary differential equations in the time variable t. Subsequently, the adjoint system of first-order ordinary differential equations is channeled through the Numerical Method of Lines and the powerful fourth-order Runge–Kutta algorithm. The numerical solution of the adjoint system of first-order ordinary differential equations can be carried out by heat transfer students employing appropriate routines embedded in the computer codes Maple, Mathematica, Matlab, and Polymath. For comparison, the baseline solutions used are the exact, analytical temperature distributions that are available in the heat conduction literature.

Cell thermoregulation hypothesis: its origin, material basis, mechanisms and meaning

The accumulated knowledge about the chromosome structure, redundant DNA and an interphase nucleus inevitably raises, at least, two questions: (1) Why are there so much non-coding DNAs in chromosomes of higher eukaryotes and (2) what is the role of their organization in interphase nucleus on cellular function? These questions in cell biology are attracting increased attention as the genomes of higher eukaryotes are being sequenced. Based on investigations of chromosomal heterochromatin regions variability in human populations, condensed chromatin (CC), interphase nucleus and redundant non-coding DNAs in the genome, an attempt is made to justify the view of possible participation of CC in cell thermoregulation. CC, being the densest domains in a cell, apparently conducts heat between the cytoplasm and nucleus when there is a difference in temperature between them. Keywords: Cell Thermoregulation; Condensed Chromatin; Q-heterochromatin; C-heterochromatin; Human Body Heat Conductivity; Human Adaptation

Cell Thermoregulation: Reality or just a logical Construction?

The existence of biological thermoregulation at the molecular and organism (physiological organ-based system of thermoregulation) levels is well known. The possibility of thermoregulation at the level of individual cells is discussed. By cell thermoregulation (CT) is meant the elimination of the temperature difference between the nucleus and cytoplasm, when, for one reason or another, the level of thermal energy in the nucleus becomes higher than of the cytoplasm. The CT hypothesis can shed light on some scattered facts and observations, known in different areas of biology and medicine, but without rational explanation. It is assumed that CT originated from the evolution of ncDNAs in the eukaryotic genome, and its material basis is condensed chromatin. Although the CT hypothesis has not yet been directly experimentally confirmed, nevertheless, its existence can be determined by indirect methods at the organism level. Keywords: Cell thermoregulation; Condensed chromatin; Chromosomal heterochromatin regions; Human body heat conductivity

New Galerkin-vector theory and efficient numerical method for analyzing steady-state heat conduction in inhomogeneous bodies subjected to a surface heat flux

This paper reports a new semi-analytical model, together with core analytical solutions, for solving steady-state heat-conduction problems involving materials of a semi-infinite matrix embedded with arbitrarily distributed inhomogeneities, and a novel fast computing algorithm for model construction. The thermal field is analyzed as the summation of the solution to the homogeneous matrix and the variations caused by the inhomogeneities. The former is obtained through the route of discrete convolution and FFT/Influence coefficients/Green’s function, and the surface heat flux via the conjugate gradient method (CGM). The eigentemperature gradient of the latter is tackled with the numerical equivalent inclusion method (EIM) based on the new analytical formulas for the disturbed temperature and heat flux from the Galerkin vectors. The influences of inhomogeneity shape, location, and heat-conduction properties are studied, and the thermal fields affected by multi-inhomogeneities in a layered form and with a regular or a random distribution are investigated.

Chromosomal Q-heterochromatin Variability and Sport

In the process of studying the variability of chromosomal Q-heterochromatin regions (Q-HRs) in human populations living permanently in different climatogeographic conditions of Eurasia and Africa, as well as in newcomers, who have successfully adapted to some extreme natural conditions, the data were obtained that, perhaps, the amount of this genetic material in the genome may be important for some sports. In particular, it turned out that in the genome of mountaineers the number of chromosomal Q-HRs was significantly lower than in the control sample and was close to that of the high-altitude natives. The same results were obtained in a comparative study of newcomers who have been working in the extreme climatic conditions of the Far North of West Siberia. We believe that these observations can be explained by cell thermoregulation (??) the level of which depends on the number of chromosomal Q-HRs. The essence of ?? is elimination of the temperature difference between the nucleus and cytoplasm. The effect of CT can be indirectly assessed by the level of the body heat conductivity (BHC). An individual with high BHC cannot make much progress in mountaineering and water sports due to the fact that their body cools rapidly. However, this individual can be more successful in sports which require effective heat-loss. Keywords: Chromosomal Q-heterochromatin; Cell thermoregulation; Body heat conductivity; Sport genetics; Marathon, Mountaineering

Human adaptation: why only genes?

Adaptation of a human to different climatic and geographical conditions has two principal features: a) only man managed to master the entire land of the Earth, while remaining a single, tropical biological species (Homo sapiens sapiens); b) in contrast to animals, human colonization of all climatic-geographical provinces, including the extreme ones (Far North and high-altitude), occurred in a very short period of time. It remains unclear how it all was managed by a human. Regarding genetic mechanisms, the main question is not clarified: did a human adapt only with the help of genes, like all other living organisms, or did he use a means inherent only in H.s.sapiens? Our nearly half a century experience of studying the genetic mechanisms of human adaptation to the high-altitude climate of the Pamir and Tien-Shan, as well as to the Far North of Eastern Siberia, argues in favor of the non-gene part of the genome. Keywords: Human adaptation; Cell thermoregulation; Hypobaric hypoxia; Chromosomal Q-heterochromatin; Human body heat conductivity