Quasi-Steady-State Temperature Distribution in Periodically Contacting Finite Regions

1981 ◽  
Vol 103 (4) ◽  
pp. 739-744 ◽  
Author(s):  
B. Vick ◽  
M. N. O¨zis¸ik
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Steady State ◽  
Temperature Distribution ◽  
Interface Temperature ◽  
Quasi Steady State ◽  
Exact Analytical Solutions ◽  
One Dimensional ◽  
Steady State Temperature ◽  
Regular Cycle

Heat transfer across two surfaces which make and break contact periodically according to a continuous regular cycle is investigated theoretically and exact analytical solutions are developed for the quasi-steady-state temperature distribution for a two-region, one-dimensional, periodically contacting model. The effects of the Biot number, the thermal conductivity and thermal diffusivity of the materials and the duration of contact and break periods on the interface temperature and the temperature distribution within the solids are illustrated with representative temperature charts.

Thermodynamic technique for the quantification of regional blood flow

1980 ◽  
Vol 238 (5) ◽  
pp. H682-H696
Author(s):  
T. Adams ◽  
S. R. Heisey ◽  
M. C. Smith ◽  
M. A. Steinmetz ◽  
J. C. Hartman ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Analysis ◽  
Blood Flow ◽  
Steady State ◽  
Regional Blood Flow ◽  
Local Blood Flow ◽  
Metabolic Heat ◽  
Steady State Temperature ◽  
Thermal Steady State

A method is described to quantify regional blood flow by thermal analysis. A weak temperature field is established in a tissue and for a thermal steady state, unidirectional heat flux and the associated temperature gradient are measured simultaneously across a small fixed segment of the tissue. This information is evaluated with probe calibrations for homogeneous isotropic fluids, with data from ancillary measurements in the nonperfused tissue and with values of specific heat and density of blood to express local blood flow in heat transfer [effective thermal conductivity (W. degrees C-1 . cm-1 x 10(-3) and/or in perfusion (ml . min-1 . cm-3)] terms. The technique measures local perfusion in small tissue volumes and is usable in acute or chronic experiments. Its accuracy is not a function of the absolute steady-state temperature of the tissue or of its metabolic heat production.

Steady-state heat sink analysis for two-terminal microwave oscillator devices with temperature dependent thermal conductivity

1993 ◽  
Vol 441 (1911) ◽  
pp. 181-189 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Steady State ◽  
Temperature Distribution ◽  
Temperature Rise ◽  
Heat Sink ◽  
Maximum Temperature ◽  
Microwave Oscillators ◽  
Steady State Temperature ◽  
Steady State Heat

A theoretical analysis to calculate the steady-state temperature distribution within a cylindrical heat sink configuration, where the thermal conductivity is dependent on the temperature, is outlined. The analysis applies to any heat sink arrangement that can be treated as one or more homogeneous solid cylinders mounted on a semi-infinite heat sink, where the heat flux incident on both faces of each cylinder is uniform over a given centralized circular region. The model is used to analyse the temperature distribution within the heat sink configurations used commonly to package two-terminal semiconductor devices that are operated as sources of electromagnetic radiation in microwave oscillators. Results are presented that show how the maximum temperature rise within commercially available heat sink packages, depends on the input heat flux and the dimensions and thermal conductivity of the materials. Furthermore, results that show how the temperature rise varies across the interfaces of given heat sink configurations, similar to those used commercially, are given also.

Nonlinear effects of variable conductivities in thermistor-related problems: an explicit example

1990 ◽  
Vol 1 (3) ◽  
pp. 245-257
Author(s):  
J. H. Young ◽  
G. Tenti
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Temperature Distribution ◽  
Surface Temperature ◽  
Nonlinear Partial Differential Equations ◽  
Electrical Potential ◽  
Nonlinear Effects ◽  
Electrical Current ◽  
Electrical Heating ◽  
One Dimensional

The coupled nonlinear partial differential equations obeyed by the electrical potential and temperature distribution for a medium undergoing steady state electrical heating are applied to a one-dimensional rod having its surface temperature held constant as current is conducted along its length due to a potential difference maintained between its ends. Extension is given to the previously discussed class of solutions by the inclusion of a thermal conductivity which varies linearly with temperature. The resulting electrical current and resistance are found to be significantly influenced by the thermal conductivity of the medium. Molybdenum is identified as a material exemplifying such a thermal conductivity and the general effects are then numerically illustrated.

On the stability of a plane deflagration wave

1959 ◽  
Vol 253 (1274) ◽  
pp. 380-389 ◽  
Keyword(s):  
Steady State ◽  
Temperature Distribution ◽  
Explicit Solution ◽  
Lewis Number ◽  
One Dimensional ◽  
Steady State Temperature ◽  
Deflagration Wave ◽  
The Stability ◽  
Suitable Approximation ◽  
Small Disturbances

The stability of a one-dimensional deflagration wave to small disturbances was investigated. By introducing a suitable approximation to the steady-state temperature distribution and after assuming that the Lewis number of the unperturbed flow is unity, it is possible to obtain an explicit solution to the disturbance equation. It is demonstrated that within the framework of the present analysis the deflagration wave appears to be stable.

scholarly journals Isostasy, LAB and some properties of asthenosphere in chosen regions of Poland

2019 ◽  
Author(s):  
Leszek Czechowski
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Temperature Distribution ◽  
Density Distribution ◽  
Depth Range ◽  
Continental Lithosphere ◽  
Isostatic Compensation ◽  
Average Value ◽  
Steady State Temperature

We use programs from the package LABWA2015 to determine position of Lithosphere-Asthenosphere Boundary (LAB) and some properties of lower lithosphere in chosen sites in Poland. Seismic, topographic, thermal and petrological data are used together with assumption about isostasy. Moreover we investigate the role of assumption about the steady state temperature distribution. We have found that sometimes this assumption for continental lithosphere can be unjustified but usually does not lead to significant errors. We have found also that in chosen sites, the thermal LAB is in the depth range 85-95 km. The average value of thermal conductivity of mantle is ~4 W m-1 K-1. Just below MOHO, a level of approximate isostatic compensation is found. More precise compensation is found in the asthenosphere at ~110 km but its position is sensitive to the density distribution.

scholarly journals Conjugate heat transfer performance of stepped lid-driven cavity with Al2O3/water nanofluid under forced and mixed convection

2021 ◽  
Vol 3 (6) ◽  
Author(s):  
Naveen Janjanam ◽  
Rajesh Nimmagadda ◽  
Lazarus Godson Asirvatham ◽  
R. Harish ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Mixed Convection ◽  
Conjugate Heat Transfer ◽  
Heat Transfer Performance ◽  
Pure Water ◽  
Interface Temperature ◽  
Transfer Model ◽  
Transfer Performance ◽  
Driven Cavity

AbstractTwo-dimensional conjugate heat transfer performance of stepped lid-driven cavity was numerically investigated in the present study under forced and mixed convection in laminar regime. Pure water and Aluminium oxide (Al2O3)/water nanofluid with three different nanoparticle volume concentrations were considered. All the numerical simulations were performed in ANSYS FLUENT using homogeneous heat transfer model for Reynolds number, Re = 100 to 500 and Grashof number, Gr = 5000, 13,000 and 20,000. Effective thermal conductivity of the Al2O3/water nanofluid was evaluated by considering the Brownian motion of nanoparticles which results in 20.56% higher value for 3 vol.% Al2O3/water nanofluid in comparison with the lowest thermal conductivity value obtained in the present study. A solid region made up of silicon is present underneath the fluid region of the cavity in three geometrical configurations (forward step, backward step and no step) which results in conjugate heat transfer. For higher Re values (Re = 500), no much difference in the average Nusselt number (Nuavg) is observed between forced and mixed convection. Whereas, for Re = 100 and Gr = 20,000, Nuavg value of mixed convection is 24% higher than that of forced convection. Out of all the three configurations, at Re = 100, forward step with mixed convection results in higher heat transfer performance as the obtained interface temperature is lower than all other cases. Moreover, at Re = 500, 3 vol.% Al2O3/water nanofluid enhances the heat transfer performance by 23.63% in comparison with pure water for mixed convection with Gr = 20,000 in forward step.

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