Transient Thermoelastic Analysis of a Solid Cylinder Containing a Circumferential Crack Using the C–V Heat Conduction Model

This article presents the transient thermoelastic analysis in a long solid cylinder with a circumferential crack using the C–V heat conduction theory. The outer surface of the cylinder is subjected to a sudden temperature change. The Laplace transform technique is adopted to solve the one-dimensional hyperbolic heat conduction equation, and the axial thermal stress is obtained for the un-cracked cylinder in the Laplace domain. Then this axial thermal stress with a minus sign is applied to the crack surface to form a mixed boundary value problem in the cylindrical coordinate system. A singular integral equation is derived by applying the Fourier and Hankel transforms to solve the mode I crack problem. The transient thermal stress intensity factors are obtained by solving the singular integral equation numerically. The influences of thermal relaxation time, crack geometry, and Biot's number upon transient temperature distributions, axial stress fields, and stress intensity factors are analyzed.     

Transient Response of Thermoelastic Hollow Sphere Under Thermal Shocks

The thermoelastotransient response in a hollow sphere under different thermal shocks is analyzed. Coupled thermal stress and non-Fourier heat conduction are considered in the mathematic model. The systems of heat and motion equations are successfully uncoupled before Laplace transformation, and an analytic solution is given. By means of numerical Laplace inversion, the temperature and stress distributions are presented. From the numerical results from different thermal shocks, the influence of the impact speed to the coupled thermal stress problems can be observed. A comparison of temperature and stress distribution is given between the coupled thermal stress problems and static thermoelastic problems.     

Thermodynamically consistent description of heat conduction with finite speed of heat propagation

In this work, governing equations for heat conduction with finite speed of heat propagation are derived directly from classical thermodynamics. For a one-dimensional flow of heat, the developed governing equation is linear and of parabolic type. In a three dimensional case, the system of nonlinear equations is formulated.Analytical solutions of the equations for one-dimensional flow of heat are obtained, and their analysis shows characteristic features of heat propagation with finite speed, being fully consistent with classical thermodynamics.     

Influence of wind power,plug-in electric vehicles,and heat storages on power system investments

Due to rising fuel costs, the substantial price for CO₂ emissions and decreasing wind power costs, wind power might become the least expensive source of power for an increasing number of power systems. This poses the questions of how wind power might change optimal investments in other forms of power production and what kind of means could be used to increase power system flexibility in order to incorporate the variable power production from wind power in a cost-effective manner.     

Theory of thermal resistance between solids with randomly sized and located contacts

Linear superposition method is used to determine an analytical solution of the thermal constriction resistance adapted to random contacts. The contact area is constituted of numerous disks which have different radii and are randomly distributed over a square or circular area. The developed solution is easy to use and allows to consider numerous contacts at a reasonable computing time. The disks can be distributed in entire contact surface or located in a specific region. The results are in an excellent agreement with available data in the literature for identical and regular contacts. The model is used to study the thermal constriction resistance evolution as a function of contact disorders, number and sizes of disks and relative contact size area. The results are compared to the model of regular contacts.     

A study on the new separate heat pipe refrigerator and heat pump

A new separate heat pipe refrigerator and heat pump is suggested based on the general three temperature thermal jet refrigerator and heat pump cycle. Sub-cooled hot water or other appropriate liquid heated by low grade heat sources forms the hot end and another heat pipe containing evaporator and condenser ends, adiabatic section of two-phase ejector and throttling tube is as the cold end of the separate heat pipe system. Performance relations for the thermal jet refrigerator and heat pump of such system is analyzed and a method of thermodynamic performance analysis is recommended. Primary prediction shows the feasibility of such heat pipe system for cold and warm water supply.     

Thermal stress induced by electric current in the vicinity of an elliptic inclusion in an infinite plate

We consider an elliptic inclusion embedded in an infinite plate subjected to the simultaneous effects of electric current and energy flux at infinity. Using complex variable methods, we analyze the resulting mechanical properties of the composite, in particular around the perimeter of the inclusion. In doing so, we find that thermal stress can exist even in a simply connected region as a result of Joule heating which can therefore be used to preset stress in manufactured devices. In the particular case of the elliptic inclusion, we find that the electric current has the ability to transfer thermal stress to regions of lower temperature thereby improving security and reliability of the corresponding devices.     

降低压力容器设计制造应力集中的措施

分析了压力容器应力集中的产生原因以及应力集中造成的危害,简要说明降低应力集中的几项措施。通过采用降低应力集中的措施,保证或延长了压力容器的使用寿命,从而节约了生产成本。     

Determination of nanolayer thickness for a nanofluid

Recent core–shell–medium models as a modification of the traditional effective medium theories for explaining the enhanced thermal conductivity of nanofluids are semi-empirical. Generally, the resulting thickness and conductivity of the nanolayer both have to be chosen to match the measured thermal conductivity of the nanofluid. Here, we attempt to find a more systematic procedure to determine the nanolayer thickness and the thermal conductivity profile within the nanolayer. An expression for the nanolayer thickness is derived by manipulation of the three basic heat conduction regions. Comparison of the estimated thermal conductance with known experimental data and thermal diffusion length are made.     

Compact cooler for electronics on the basis of a pulsating heat pipe

The paper presents the results of developing and investigating a compact cooler for electronics made on the basis of a closed loop pulsating heat pipe (CLPHP). The cooler is made of a copper tube 5.6 m long with OD of 2 mm and ID of 1.2 mm in the form a 3D spiral containing 17 turns. The device is equipped with a light copper radiator with a finning area of 1670 cm², which was blown by an axial fan located inside the spiral. The thermal interface of the cooler situated in the heating zone is made of a copper plate with a thermocontact surface measuring 40 × 35 mm, which was in thermal contact with all the turns of the device. The cooler overall dimensions are 105 × 100 × 60 mm, its mass is 350 g.The operation of the cooler has been investigated with water, methanol and R141b as working fluids at a uniform and concentrated supply of a heat load in different heating modes. A reliable operation of the device has been demonstrated in the range of heat loads from 5 to 250 W. A minimum thermal resistance “heat source–ambient air” equal to 0.32 °C/W was attained with water and methanol as working fluids at a uniform heat load of 250 W. With a heat load concentrated on a section of the thermal interface limited by an area of 1 cm², a minimum value of thermal resistance equal to 0.62 °C/W was attained at a heat load of 125 W when methanol was used as a working fluid.     

Two-Dimensional Problem of a Crack in Thermoelectric Materials

The two-dimensional problem of a crack in thermoelectric materials is studied in this research. The general solution is derived based on the complex variable method. For the case of a crack subjected to remote electric current and heat flow, the solutions are obtained in closed-form. The results show that the fields of heat flow, electric current, and stress exhibit traditional square-root singularity at the crack tip. The remote electric current produces both type I and II stress intensity factor. Furthermore, the stress intensity factor has a linear relationship with the heat flux, but a non-linear relationship with the electric current.     

Integrated Photoelasticity for Axisymmetric Thermal Stress Measurement Using the Stress Function

By investigating axisymmetric stress fields with integrated photoelasticity, the stress components σ_z and σ_rz can be determined directly from the experimental data. Stress components σ_r and σ_θ are usually determined using the equilibrium and compatibility equations. In this article it is shown that the stress function for an axisymmetric thermoelastic stress field can be determined on the basis of experimental data, obtained with integrated photoelasticity. Knowledge of the stress function permits one to calculate all the stress components as well as the temperature field in the test object.