Extremal temperature fields and stresses of a spherical shell under local heating

1970 ◽  
Vol 6 (12) ◽  
pp. 1334-1339
Author(s):  
Ya. I. Burak ◽  
Yu. D. Zozulyak
Keyword(s):  
Spherical Shell ◽  
Local Heating ◽  
Temperature Fields ◽  
Extremal Temperature

scholarly journals Convection regimes induced by local boundary heating in a liquid–gas system

2019 ◽  
Vol 873 ◽  
pp. 441-458 ◽  
Author(s):  
Victoria B. Bekezhanova ◽  
A. S. Ovcharova
Keyword(s):  
Gas Flow ◽  
Stokes Equations ◽  
Local Heating ◽  
Fluid Motion ◽  
Lower Boundary ◽  
Conjugate Problem ◽  
Temperature Fields ◽  
Layer System ◽  
Local Boundary ◽  
The Impact

In the framework of the complete formulation of the conjugate problem, the liquid–gas flow structure arising upon local heating using thermal sources is investigated numerically. The two-layer system is confined by solid impermeable walls. The Navier–Stokes equations in the Boussinesq approximation in the ‘streamfunction–vorticity’ variables are used to describe the media motion. The dynamic conditions at the interface are formulated in terms of the tangential and normal velocities, while the temperature conditions at the external boundaries of the system take into account the presence of local heaters. The influence of the number of heaters and heating modes on the dynamics and character of the appearing convective regimes is analysed. The steady and commutated heating modes for one and two heaters arranged at the lower boundary are investigated. The heating initiates convective and thermocapillary mechanisms causing the fluid motion. Transient regimes with the successive formation of two-vortex, quadruple-vortex and two-vortex flows are observed before the stabilization of the system in the uniform heating mode. A stable thermocapillary deflection appears at the interface above the heater. The commutated mode of heating entails oscillations of the interface with a change in the deflection form and the formation of travelling vortices in the fluids. The impact of particular mechanisms on the flow patterns is analysed. The paper presents typical distributions of the velocity and temperature fields in the system and the position of the interface for the considered cases.

Analysis and Design of Small Scale Pipe Forge Welding Process

2013 ◽  
Author(s):  
Junyan Liu ◽  
Ganesan S. Marimuthu ◽  
Per Thomas Moe
Keyword(s):  
High Speed ◽  
Pipe Wall ◽  
Local Heating ◽  
Welding Process ◽  
Axial Direction ◽  
Temperature Fields ◽  
Small Scale ◽  
Electromagnetic Modeling ◽  
Analysis And Design ◽  
Welding Machine

Shielded Active Gas Forge Welding is a high speed welding method for joining inter alia steel pipeline and casing. The process consists of a heating step, in which the bevels of the sections to be joined are heated locally to temperatures exceeding 1000 °C, and a subsequent forging step in which joining takes place by the application of a high axial force. In order to make possible cost-effective welding qualification and research a small scale forge welding machine has been developed. Down-scaling of the forge welding process should be carefully assessed in order to establish the limits of the process. In this paper two aspects of the forge welding process have been studied in detail by the use of finite element modeling and experiments: a) coupled thermal and electromagnetic modeling of heating and b) coupled thermo-mechanical modeling of forging. Special attention is given to the study of the limits of buckling of the pipe wall during forging. A high thermal gradient in the axial direction in the pipe wall facilitates local plastic deformation during forging and proper fusion of welds. For elongated temperature fields buckling is more likely to occur since the effective stiffness of the wall section is reduced. The limits of buckling depend on the wall thickness and diameter of section to be joined. While the forge welding process works very well for virtually all types of full scale pipeline and casing sections, buckling has been observed when joining very thin-walled small scale pipes. For welding of stainless steel small scale pipes local heating proves challenging. These challenges may be overcome by innovative welding machine design, and by carefully assessing welding process limitations. Certain physical limitations must still be considered.

scholarly journals Entropy Generation Analysis of Natural Convection in Square Enclosures with Two Isoflux Heat Sources

2017 ◽  
Vol 7 (2) ◽  
pp. 1486-1495
Author(s):  
S. Z. Nejad ◽  
M. M. Keshtkar
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Local Heating ◽  
Heat Sinks ◽  
Temperature Fields ◽  
Entropy Generation Rate ◽  
Heat Sources ◽  
Minimum Entropy ◽  
Adiabatic Flow ◽  
Heater Length

This study investigates entropy generation resulting from natural convective heat transfer in square enclosures with local heating of the bottom and symmetrical cooling of the sidewalls. This analysis tends to optimize heat transfer of two pieces of semiconductor in a square electronic package. In this simulation, heaters are modeled as isoflux heat sources and sidewalls of the enclosure are isothermal heat sinks. The top wall and the non-heated portions of the bottom wall are adiabatic. Flow and temperature fields are obtained by numerical simulation of conservation equations of mass, momentum and energy in laminar, steady and two dimensional flows. With constant heat energy into the cavity, effect of Rayleigh number, heater length, heater strength ratios and heater position is evaluated on flow and temperature fields and local entropy generation. The results show that a minimum entropy generation rate is obtained under the same condition in which a minimum peak heater temperature is obtained.

Three-dimensional thermal convection in a spherical shell

1989 ◽  
Vol 206 ◽  
pp. 75-104 ◽  
Author(s):  
D. Bercovici ◽  
G. Schubert ◽  
G. A. Glatzmaier ◽  
A. Zebib
Keyword(s):  
Heat Flow ◽  
Spherical Shell ◽  
Thermal Convection ◽  
Flow Direction ◽  
Three Dimensional ◽  
Maximum Velocity ◽  
Temperature Fields ◽  
Free Boundaries ◽  
Onset Of Convection ◽  
Axisymmetric Solution

Independent pseudo-spectral and Galerkin numerical codes are used to investigate three-dimensional infinite Prandtl number thermal convection of a Boussinesq fluid in a spherical shell with constant gravity and an inner to outer radius ratio equal to 0.55. The shell is heated entirely from below and has isothermal, stress-free boundaries. Nonlinear solutions are validated by comparing results from the two codes for an axisymmetric solution at Rayleigh number Ra = 14250 and three fully three-dimensional solutions at Ra = 2000, 3500 and 7000 (the onset of convection occurs at Ra = 712). In addition, the solutions are compared with the predictions of a slightly nonlinear analytic theory. The axisymmetric solution is equatorially symmetric and has two convection cells with upwelling at the poles. Two dominant planforms of convection exist for the three-dimensional solutions: a cubic pattern with six upwelling cylindrical plumes, and a tetrahedral pattern with four upwelling plumes. The cubic and tetrahedral patterns persist for Ra at least up to 70000. Time dependence does not occur for these solutions for Ra [les ] 70000, although for Ra > 35000 the solutions have a slow asymptotic approach to steady state. The horizontal and vertical structure of the velocity and temperature fields, and the global and three-dimensional heat flow characteristics of the various solutions are investigated for the two patterns up to Ra = 70000. For both patterns at all Ra, the maximum velocity and temperature anomalies are greater in the upwelling regions than in the downwelling ones and heat flow through the upwelling regions is almost an order of magnitude greater than the mean heat flow. The preferred mode of upwelling is cylindrical plumes which change their basic shape with depth. Downwelling occurs in the form of connected two-dimensional sheets that break up into a network of broad plumes in the lower part of the spherical shell. Finally, the stability of the two patterns to reversal of flow direction is tested and it is found that reversed solutions exist only for the tetrahedral pattern at low Ra.

Use of Renewable Energy for Local Heating of Piglets

2021 ◽  
Vol 3 (44) ◽  
pp. 104-110
Author(s):  
Stanislav S. Trunov ◽  
◽  
Dmitriy A. Tikhomirov ◽  
Aleksey V. Khimenko ◽  
Aleksey V. Kuz’michev ◽  
...  
Keyword(s):  
Thermal Energy ◽  
Local Heating ◽  
Thermoelectric Module ◽  
Heat Removal ◽  
Heat Pipes ◽  
Cold Season ◽  
Temperature Fields ◽  
Thermoelectric Modules ◽  
Suckling Piglets ◽  
Heat Released

The analysis of technologies and technical means of creating a temperature regime in the piglet location zone, where two different temperature fields must be created in the cold season: one for breeding pigs, the other for suckling piglets. The article considers the question of the use of thermoelectric modules and heat pipes as a source of thermal energy in local heating installations for suckling piglets. (Research purpose) There are proposed the functional and technological scheme of the installation for local heating of young animals with the use of thermoelectric modules and heat pipes. (Materials and methods) In the developed scheme, the thermal energy of the hot circuit of thermoelectric modules is used to heat the site on which the piglets are located. (Results and discussion) The heat of the cold circuit of the thermoelectric module assimilates the thermal energy of the removed ventilation air. For the effective operation of a thermoelectric installation for local heating of piglets, it is necessary that the cooling circuit, which absorbs thermal energy from the environment, be involved in some technological process for heat removal, for example, the heated ventilation air being removed. This leads to a significant increase in the efficiency of thermoelectric modules. At the same time, the installation will operate in the heat pump mode, since the amount of heat released in the heat exchanger of the hot circuit of the thermoelectric assembly exceeds the amount of electricity consumed from the network. (Conclusions) The article presents the sample of a thermoelectric installation was developed and its laboratory tests. The article describes the energy efficiency of the use of thermoelectric modules as energy converters in thermal technological processes.

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