Temperature Gradients in Skirt Supports of Hot Vessels

1963 ◽  
Vol 85 (2) ◽  
pp. 219-223 ◽  
Author(s):  
D. J. Bergman
Keyword(s):  
Steady State ◽  
Temperature Gradient ◽  
Temperature Curve ◽  
Neutral Axis ◽  
Temperature Gradients ◽  
Radius Of Curvature ◽  
Maximum Gradient ◽  
Axial Tension ◽  
Steady State Temperature ◽  
Tension And Compression

A discussion of the variables involved in the temperature gradient along a skirt support for a hot vessel is presented. A method is presented for reasonably approximating the maximum gradient since the temperature curve is rarely linear. For guidance in applying the formula and to illustrate the effect of some of the variables, several basic cases are calculated, using three different skirt support thicknesses and considering bare, fireproofed, and insulated types of skirts. Having a formula for a steady-state temperature along the length of a skirt, it is possible by means of mathematical manipulations to obtain the value of the radius of curvature of the neutral axis at any point. Using this, it is then possible to calculate the axial tension and compression stresses on the inside and outside of a free skirt wall.

Suppression of photorefractive damage with aid of steady-state temperature gradient in nominally pure LiNbO3 crystals

2008 ◽  
Vol 104 (11) ◽  
pp. 114104 ◽  
Author(s):  
S. M. Kostritskii ◽  
O. G. Sevostyanov ◽  
M. Aillerie ◽  
P. Bourson
Keyword(s):  
Steady State ◽  
Temperature Gradient ◽  
Steady State Temperature

Steady State Temperature Gradients in a Non-Blinking Human Eye Prepared for Surgery

2013 ◽  
Author(s):  
Amanie N. Abdelmessih
Keyword(s):  
Steady State ◽  
Laser Surgery ◽  
Room Temperature ◽  
Contact Lenses ◽  
High Heat ◽  
Temperature Gradients ◽  
Human Eye ◽  
Steady State Temperature ◽  
Heat Effects ◽  
Exact Temperature

LASER surgery on the human eye is intended to reduce a person’s dependency on glasses or contact lenses. Any type of Laser surgery has heat effects on the eye. In laser surgery specific parts of the eye are exposed to concentrated high heat doses, too high heat at a certain spot results in permanent medical damage to the specific exposed eye cells. Precise temperature monitoring of the live interior of the human eye is not possible with the current technology. Published modeling assumes that the human eyeball is at a constant temperature, mostly at 37 °C. Understanding the exact temperature gradients in the prepared open human eyeball in room temperature before surgery is a first step in better understanding the heat effects of either laser surgery on specific treated spots of the cornea, or the effects of insertion of synthetic lenses in the human eye, or treating the retina with laser. In this article the anatomy of the human eyeball, dimensions, and properties are considered in constructing a finite element steady state thermal model of the normal open human eye for an adult, in preparation for surgery under normal room conditions. Also, room boundary conditions are used. Based on the model, the temperature gradients in the open eye are reported.

scholarly journals Spatial temperature mapping within polymer nanocomposites undergoing ultrafast photothermal heating via gold nanorods

Nanoscale ◽  
2014 ◽  
Vol 6 (24) ◽  
pp. 15236-15247 ◽  
Author(s):  
Somsubhra Maity ◽  
Wei-Chen Wu ◽  
Chao Xu ◽  
Joseph B. Tracy ◽  
Kenan Gundogdu ◽  
...  
Keyword(s):  
Steady State ◽  
Temperature Gradient ◽  
Polymer Nanocomposites ◽  
Gold Nanorods ◽  
Direct Detection ◽  
Polymer Melt ◽  
Polarized Fluorescence ◽  
Temperature Mapping ◽  
Photothermal Heating ◽  
Steady State Temperature

Polarized fluorescence temperature measurements combined with direct detection of nanorod rotation within the polymer melt regions reveal the steady-state temperature gradient on the nanoscale.

scholarly journals Issues of conventional model of transfer of latent heat in soil

2017 ◽  
Vol 31 (2) ◽  
pp. 303-306
Author(s):  
Iwao Sakaguchi ◽  
Hidetoshi Mochizuki ◽  
Arata Katayama ◽  
Toshihiko Momose ◽  
Haruyuki Fujimaki
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Temperature Gradient ◽  
Latent Heat ◽  
Conventional Model ◽  
Solute Content ◽  
Steady State Condition ◽  
Steady State Temperature ◽  
Vapour Flux ◽  
Temperature Water

Abstract Upper limit of experimental coefficient between the measured transfer of latent heat and the estimated vapour flux in the frame of the conventional model of latent heat transfer in soil was examined by analysing the measured latent heat transfer and temperature gradient in soil under steady-state temperature gradient. To exclude the temperature gradient as an uncertainty factor from the experimental coefficient, the temperature gradients of overall soil and soil pore were included into the vapour fluxes in the atmosphere. The estimated experimental coefficient did not exceed unity, which indicated that both the latent heat transfer and the vapour fluxes in the soil were smaller than those in the atmosphere. The gap that appeared between the experimental coefficient and the product of the tortuosity factor and air-filled porosity implied the existence of an unidentified parameter relevant to characteristic of the circulation of water in soil which is the main mechanism of latent heat transfer in soil. By quantifying this characteristic with simultaneous measurements of the latent heat transfer, distributions of temperature, water content and solute content in various soils under the steady-state condition, the conventional model would be modified, or an alternative model being independent of the conventional model would be developed.

Thermal Stresses in Bodies Exhibiting Temperature-Dependent Elastic Properties

1952 ◽  
Vol 19 (3) ◽  
pp. 350-354
Author(s):  
H. H. Hilton
Keyword(s):  
Temperature Gradient ◽  
Elastic Properties ◽  
Plane Stress ◽  
Material Properties ◽  
Thermal Stresses ◽  
Temperature Gradients ◽  
Temperature Dependent ◽  
Steady State Temperature ◽  
Specific Temperature ◽  
Walled Cylinder

Abstract Expressions are derived for thermal stresses and strains due to a steady-state temperature gradient in a thick-walled cylinder and a circular thin plate, made of a material having temperature-dependent elastic properties. Two numerical examples are computed for specific temperature gradients and temperature-dependent elastic properties, which yield results showing that the maximum thermal stresses are appreciably lower and the maximum thermal strains are larger than the corresponding values obtained for temperature-independent properties. The validity of the thermal plane-stress assumptions is investigated and it is shown that such solutions, regardless of whether the material properties are temperature-dependent or constant, are only approximations. The smaller the temperature gradient the more closely are the plane-stress assumptions satisfied.

Synthesis of chalcogenide and pnictide crystals in salt melts using a steady-state temperature gradient

2016 ◽  
Vol 61 (4) ◽  
pp. 682-691 ◽  
Author(s):  
D. A. Chareev ◽  
O. S. Volkova ◽  
N. V. Geringer ◽  
A. V. Koshelev ◽  
A. N. Nekrasov ◽  
...  
Keyword(s):  
Steady State ◽  
Temperature Gradient ◽  
Salt Melts ◽  
Steady State Temperature

Methodology of studying the mechanical properties of composite materials (reinforced concrete)

2018 ◽  
Vol 84 (12) ◽  
pp. 61-67
Author(s):  
V. A. Eryshev
Keyword(s):  
Mechanical Properties ◽  
Reinforced Concrete ◽  
Experimental Studies ◽  
Analytical Relationship ◽  
Hardened Concrete ◽  
Deformation Model ◽  
Joint Work ◽  
Concrete Shrinkage ◽  
Axial Tension ◽  
Tension And Compression

The mechanical properties of a complex composite material formed by steel and hardened concrete, are studied. A technique of operative quality control of new credible concrete and reinforcement, both in laboratory and field conditions is developed for determination of the strength and strain characteristics of materials, as well as cohesion forces determining their joint operation under load. The design of the mobile unit is presented. The unit provides a possibility of changing the direction of loading and testing the reinforced element of the given shape both for tension and compression. Moreover, the nomenclature of testing equipment and the number of molds for manufacturing concrete samples substantially decrease. Using the values of forcing resulting in concrete cracking when the joint work of concrete and reinforcement is disrupted the values of the inherent stresses and strains attributed to the concrete shrinkage are determined. An analytical relationship between the forces and deformations of the reinforced concrete sample with central reinforcement is derived for axial tension and compression, with allowance for strains and stresses in the reinforcement and concrete resulted from concrete shrinkage. The results of experimental studies are presented, including tension diagrams and diagrams of developing axial deformations with an increase in the load under the central loading of the reinforced elements. A methodology of accounting for stresses and deformations resulted from concrete shrinkage is developed. The applicability of the derived analytical relationships between stresses and deformations on the material diagrams to calculations of the reinforced concrete structures in the framework of the deformation model is estimated.

scholarly journals Identification of DC Thermal Steady-State Differential Inductance of Ferrite Power Inductors

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3854
Author(s):  
Salvatore Musumeci ◽  
Luigi Solimene ◽  
Carlo Stefano Ragusa
Keyword(s):  
Steady State ◽  
Input Voltage ◽  
Switching Frequency ◽  
Ohmic Losses ◽  
Steady State Temperature ◽  
Wide Range ◽  
Average Current ◽  
Power Inductors ◽  
Saturable Inductor ◽  
Thermal Steady State

In this paper, we propose a method for the identification of the differential inductance of saturable ferrite inductors adopted in DC–DC converters, considering the influence of the operating temperature. The inductor temperature rise is caused mainly by its losses, neglecting the heating contribution by the other components forming the converter layout. When the ohmic losses caused by the average current represent the principal portion of the inductor power losses, the steady-state temperature of the component can be related to the average current value. Under this assumption, usual for saturable inductors in DC–DC converters, the presented experimental setup and characterization method allow identifying a DC thermal steady-state differential inductance profile of a ferrite inductor. The curve is obtained from experimental measurements of the inductor voltage and current waveforms, at different average current values, that lead the component to operate from the linear region of the magnetization curve up to the saturation. The obtained inductance profile can be adopted to simulate the current waveform of a saturable inductor in a DC–DC converter, providing accurate results under a wide range of switching frequency, input voltage, duty cycle, and output current values.

scholarly journals The principle of minimum entropy production and snow structure

2004 ◽  
Vol 50 (170) ◽  
pp. 342-352 ◽  
Author(s):  
Perry Bartelt ◽  
Othmar Buser
Keyword(s):  
Mass Transfer ◽  
Temperature Gradient ◽  
Entropy Production ◽  
Surface Curvature ◽  
The State ◽  
Temperature Gradients ◽  
Curvature Radius ◽  
Minimum Entropy ◽  
Snow Layer ◽  
Minimum Entropy Production

AbstractAn essential problem in snow science is to predict the changing form of ice grains within a snow layer. Present theories are based on the idea that form changes are driven by mass diffusion induced by temperature gradients within the snow cover. This leads to the well-established theory of isothermal- and temperature-gradient metamorphism. Although diffusion theory treats mass transfer, it does not treat the influence of this mass transfer on the form — the curvature radius of the grains and bonds — directly. Empirical relations, based on observations, are additionally required to predict flat or rounded surfaces. In the following, we postulate that metamorphism, the change of ice surface curvature and size, is a process of thermodynamic optimization in which entropy production is minimized. That is, there exists an optimal surface curvature of the ice grains for a given thermodynamic state at which entropy production is stationary. This state is defined by differences in ice and air temperature and vapor pressure across the interfacial boundary layer. The optimal form corresponds to the state of least wasted work, the state of minimum entropy production. We show that temperature gradients produce a thermal non-equilibrium between the ice and air such that, depending on the temperature, flat surfaces are required to mimimize entropy production. When the temperatures of the ice and air are equal, larger curvature radii are found at low temperatures than at high temperatures. Thus, what is known as isothermal metamorphism corresponds to minimum entropy production at equilibrium temperatures, and so-called temperature-gradient metamorphism corresponds to minimum entropy production at none-quilibrium temperatures. The theory is in good agreement with general observations of crystal form development in dry seasonal alpine snow.

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