Action Of Heat Flux Research Articles

Transient Thermoelastic Analysis of a Cylinder Having a Varied Coefficient of Thermal Expansion

This paper is concerned with the mathematical modeling of transient thermal elastic problem involving a layered cylinder with a varied coefficient of thermal expansion and powered by a heat flux from an external surfaces. All material's properties are the same for each cylinder's layers, besides the coefficient of linear thermal expansion which is varied and corresponds to hardened and unhardened layers. An obtained solution is a transient state of a heat transfer for the one-dimensional temperature change under the action of heat flux in continuous time. Cumbersome analytical solutions are converted into simple approximation. They are used to solve the inverse problems of the thermal stressed state–determining the time of action of the heat flux to achieve the specified maximum temperature or stress. Some numerical results for the stress distributions are shown in figures.

INTERMITTENT GRINDING TEMPERATURE MODELING FOR GRINDING SYSTEM STATE MONITORING

A dry and wet intermittent grinding temperature mathematical model for the thermal macro- or micro-cycle was developed and studied. The heating stage corresponds to the wheel cutting segment passage time through the every contact zone point. The cooling stage corresponds to the passage time of the grinding wheel groove (or pore) through the point mentioned. The dry intermit-tent grinding temperature field is formed by temperature field superposition during the indicated both heating and cooling cycle stag-es under the action of heat flux on each point of the surface being ground. While during wet intermittent grinding with grinding fluid through the grooves (or pores) of the intermittent grinding wheel, the temperature field formed at the heating stage is the initial con-dition for determining the temperature field at the forced cooling stage. Based on the obtained model of the intermittent grinding temperature field the geometrical parameters of the discontinuous (slotted, segmented, high porous) grinding wheel are found and determined for the grinding with intermittent grinding wheel as follows: the number of cutting sections on the wheel and the duty factor of the period of heat flux pulses. The wet intermittent grinding temperature field is also formed by summing (stitching) the temperature fields. However, the heat exchange of the surface being ground with the cooling medium, which periodically acts on this surface during the cooling stage, is taken into account in each macro- or micro-cycle of heat flux in intermittent grinding.The pre-sented article is the result of current work carried out as part of the scientific school of Professor A.V. Yakimov who was the founder of intermittent grinding technology and automation of grinding operations.

Investigation of the liquid metal flow in a vertical rectangular channel applied to the tokamak reactor cooling system

For realization of this project, large-scale studies of heat transfer and hydrodynamics of the flow in the channels, simulating conditions close to real are required. These conditions are primarily the flow of an electrically conducting fluid in a magnetic field and thermo-gravitational convection, emergering due to strong heat fluxes. Recently in our research group in MPEI-JIHT RAS, obtaining experimental data has become possible due to creation of model stands to identify patterns of MHD flow in a magnetic field under the action of heat flux. It is necessary simple algebraic models, resulting the main parameters of the flow and not requiring large computational resources. Besides that, obtaining experimental data will be used for validation and verification of computational codes. This project examines the influence of thermo-gravitational convection on the upward flow of a liquid metal in a rectangular channel (aspect ratio 1:3). This configuration matches to the Russian-Indian project of cooling the ITER blanket. Currently, the participants of the project are creating of a model including the influence of magnetic field on the flow. This work is dedicated to the creation of a model including the influence of thermo-gravitational convection without influence of magnetic field.

Elastic ellipsoidal heat-conducting inclusion in a body under the action of a heat flux applied at infinity

We find the exact analytic solution of the system of four singular integrodifferential equations obtained as a result of reduction of the three-dimensional thermoelastic problem for a body containing a heatconducting elastic ellipsoidal inclusion. It is assumed that the body is subjected to the action of a uniform heat flux applied at infinity in the direction perpendicular to the median plane of the inclusion. As a result, we deduce the relations for the stress concentration near the inclusion, the level of stresses inside the inclusion, and the corresponding stress intensity factors K II and K III. The influence of the configuration of the inclusion on the stress concentration and intensity is analyzed for some special cases of the problem.

Effect of artificial perturbations on the formation of structures in a nonisothermal liquid film

The effect of artificial perturbations on the formation of structures in a nonisothermal liquid film flowing down a vertical plate with a 150 × 150 mm heater has been experimentally studied. The action of heat flux on the wave flow leads to the formation of periodic flowing rivulets separated by thin film regions. Artificial perturbations in a certain interval of wavelengths produce a change in the number of rivulets formed on the heater surface. The “most dangerous” wavelength of artificial perturbations altering the flow structure is determined.

Nonstationary heat conduction over a blunt body with surface mass exchange placed in a supersonic flow

Interaction of a high-temperature gas with a heat-reflecting coating is accompanied by many interrelated processes. The need for thermal protection arises when an unprotected structure is bound to inevitably fail under the action of heat fluxes. It seems that heat fluxes on the order of 2.5 × 10 5 W/m2, which corresponds to equilibrium surface temperatures exceeding 1500 K, set the upper operating temperature limit for unprotected refractory metals. However, this limit is to some extent conditional, since mechanical and corrosion effects may often aggravate the thermal action, causing the structure to fail at much lower temperatures.

Experimental study of the wave flow of a liquid film on a heated surface

The wave flow of a water film over the surface of a vertical plate with a 150×150-mm heater has been experimentally studied. The action of heat flux on the wave flow of the liquid film is manifested by the formation of periodic flowing rivulets separated by thin film regions. The thickness of the film between rivulets was measured using a fiber optical reflection probe. As the heat flux grows, the average film thickness h continuously decreases. However, when the thickness reaches h≈0.5 h0, where h0 is the value given by the Nusselt formula for a laminar liquid film, the film exhibits spontaneous rupture. It was found that, as the local flow rate decreases, the wave amplitude in the region between rivulets drops more rapidly than expected according to the laws of “cold hydrodynamics.”

Thermal stresses in ablative composite thin-walled structures under intensive heat flow

In the present paper a theory on thin-walled shells made of ablative composite materials is developed. This theory is destined for calculation of thermostresses in thin-walled composite structures subjected to intensive action of heat fluxes. The main peculiarity of ablative shells is the appearance of essential transversal stresses that lead to cracking the shells of laminated composites. The example of numerical calculation of thermostresses in a cylindrical thin-walled ablative composite shell under one-sided intensive action of heat flux is given.

Failure of composite materials at high temperatures and finite strains

Elastomeric composite materials that are serviceable at high temperatures and finite strains are often used to protect load-bearing members of structures against the action of heat fluxes. Methods for the calculation of strain of elastomeric materials with finite strains at normal temperatures have been set forth previously. For the case of small strains, a model of strain and strength of polymeric materials can be used to predict their serviceability at high temperatures when thermal breakdown processes take place in the plates. In the present work, this model is extended to the case of finite strains.