scholarly journals Techniques for Thermal Conductivity Measurements in Antarctica

1982 ◽  
Vol 3 ◽  
pp. 96-102 ◽  
Author(s):  
Richard E. Ewing ◽  
Richard S. Falk ◽  
John F. Bolzan ◽  
Ian M. Whillans
Keyword(s):  
Thermal Properties ◽  
Mathematical Problem ◽  
Numerical Procedure ◽  
Measurement Procedure ◽  
Physical Experiment ◽  
Insufficient Data ◽  
Conductivity Measurements ◽  
Numerical Techniques ◽  
Accurate Knowledge ◽  
Well Posed

An accurate knowledge of the thermal properties of firn and ice within a glacier is essential for any reliable mathematical model of heat transfer. This paper considers the problem of determining the thermal properties of firn at Dome C, Antarctica, for use in such a model.First, the difficulties in accurately determining thermal properties are discussed. Then a physical experiment which can be performed under field conditions, but which will yield a well-posed mathematical problem for determining the unknown properties, is presented. Next, two different numerical techniques for solving the mathematical problem are discussed. Finally, some numerical approximations and error estimates are presented for the results of applying our numerical procedure to data from Dome C. Although insufficient data were obtained to test our methods fully, we have established a measurement procedure and a method of analysis which appear to be promising.

scholarly journals Techniques for Thermal Conductivity Measurements in Antarctica

1982 ◽  
Vol 3 ◽  
pp. 96-102 ◽  
Author(s):  
Richard E. Ewing ◽  
Richard S. Falk ◽  
John F. Bolzan ◽  
Ian M. Whillans
Keyword(s):  
Thermal Properties ◽  
Mathematical Problem ◽  
Numerical Procedure ◽  
Measurement Procedure ◽  
Physical Experiment ◽  
Insufficient Data ◽  
Conductivity Measurements ◽  
Numerical Techniques ◽  
Accurate Knowledge ◽  
Well Posed

An accurate knowledge of the thermal properties of firn and ice within a glacier is essential for any reliable mathematical model of heat transfer. This paper considers the problem of determining the thermal properties of firn at Dome C, Antarctica, for use in such a model.First, the difficulties in accurately determining thermal properties are discussed. Then a physical experiment which can be performed under field conditions, but which will yield a well-posed mathematical problem for determining the unknown properties, is presented. Next, two different numerical techniques for solving the mathematical problem are discussed. Finally, some numerical approximations and error estimates are presented for the results of applying our numerical procedure to data from Dome C. Although insufficient data were obtained to test our methods fully, we have established a measurement procedure and a method of analysis which appear to be promising.

Effects of Glycerol on the Thermal Properties of Phosphate Buffered Saline and Porcine Liver at Subzero Temperatures

2007 ◽  
Author(s):  
Jeung H. Choi ◽  
John C. Bischof
Keyword(s):  
Phase Transition ◽  
Thermal Properties ◽  
Property Values ◽  
Insufficient Data ◽  
Porcine Liver ◽  
Water Ice ◽  
Subzero Temperatures ◽  
Temperature Ranges ◽  
Phase Change Phenomena ◽  
Phosphate Buffered Saline

Improvements in the prediction of thermal behavior during cryosurgery and cryopreservation can help improve the outcome of these cryobiological applications. The accuracy of the models depends on numerous factors including the kinetics and energy release during phase change phenomena and knowledge of thermal properties. Furthermore, connecting the thermal properties to crystalline, amorphous, and other phases adds an important mechanistic dimension that can also improve and direct an outcome. However, insufficient data for thermal properties in the subzero domain result in reliance on property estimations based usually upon tabulated water-ice data or weight averaged values from known materials primarily in temperature ranges above −40 °C [1]. This study focused on expanding the thermal properties database for both solutions and tissues. Results for Phosphate Buffered Saline (PBS) and porcine liver with glycerol at subzero temperatures (−150 ∼ 0 °C) are reported. The shifting of thermal property values due to sample crystallization, amorphous phase transition, and melting is discussed.

scholarly journals Characterisation of Ex Vivo Liver Thermal Properties for Electromagnetic-Based Hyperthermic Therapies

Sensors ◽  
2020 ◽  
Vol 20 (10) ◽  
pp. 3004 ◽  
Author(s):  
Nuno P. Silva ◽  
Anna Bottiglieri ◽  
Raquel C. Conceição ◽  
Martin O’Halloran ◽  
Laura Farina
Keyword(s):  
Thermal Properties ◽  
Ex Vivo ◽  
Tissue Perfusion ◽  
Heating Process ◽  
Volumetric Heat Capacity ◽  
Accurate Knowledge ◽  
Different Temperatures ◽  
Treatment Plans ◽  
Specific Tissue ◽  
Tissue Target

Electromagnetic-based hyperthermic therapies induce a controlled increase of temperature in a specific tissue target in order to increase the tissue perfusion or metabolism, or even to induce cell necrosis. These therapies require accurate knowledge of dielectric and thermal properties to optimise treatment plans. While dielectric properties have been well investigated, only a few studies have been conducted with the aim of understanding the changes of thermal properties as a function of temperature; i.e., thermal conductivity, volumetric heat capacity and thermal diffusivity. In this study, we experimentally investigate the thermal properties of ex vivo ovine liver in the hyperthermic temperature range, from 25 °C to 97 °C. A significant increase in thermal properties is observed only above 90 °C. An analytical model is developed to model the thermal properties as a function of temperature. Thermal properties are also investigated during the natural cooling of the heated tissue. A reversible phenomenon of the thermal properties is observed; during the cooling, thermal properties followed the same behaviour observed in the heating process. Additionally, tissue density and water content are evaluated at different temperatures. Density does not change with temperature; mass and volume losses change proportionally due to water vaporisation. A 30% water loss was observed above 90 °C.

Transient Heat Conduction in a Rod of Finite Length With Variable Thermal Properties

1960 ◽  
Vol 27 (4) ◽  
pp. 617-622 ◽  
Author(s):  
W. H. Chu ◽  
H. N. Abramson
Keyword(s):  
Thermal Properties ◽  
Heat Conduction ◽  
Finite Length ◽  
Thermophysical Properties ◽  
Numerical Procedure ◽  
Transient Heat Conduction ◽  
Theoretical Solution ◽  
Rod Of Finite Length

This paper presents a theoretical solution for transient heat conduction in a rod of finite length with variable thermal properties. A numerical procedure is developed and the results of one example are presented and compared with the corresponding solution for the case of constant properties. Application to the problem of determination of thermophysical properties is discussed briefly.

Dynamik des Zerfalls von Inversionswänden in einem nematischen flüssigen Kristall / Dynamics of the Annihilation of Inversion Walls in a Nernatic Liquid Crystal

1974 ◽  
Vol 29 (9) ◽  
pp. 1356-1366 ◽  
Author(s):  
G. Heppke ◽  
F. Schneider
Keyword(s):  
Magnetic Field ◽  
Liquid Crystal ◽  
Electric Conductivity ◽  
Dynamic Behaviour ◽  
Numerical Procedure ◽  
Experimental Results ◽  
Conductivity Measurements

Inversion walls are generated by rotating the direction of a magnetic field by 180° with respect to the director in the homeotropically aligned nematic layer. A numerical procedure based on the Leslie-Ericksen theory allows for the calculation of the dynamic behaviour of the inversion walls. Experimental results obtained with MBBA by electric conductivity measurements show satisfying agreement with theory.

A Self-Heated Thermistor Technique to Measure Effective Thermal Properties From the Tissue Surface

1987 ◽  
Vol 109 (4) ◽  
pp. 330-335 ◽  
Author(s):  
P. A. Patel ◽  
J. W. Valvano ◽  
J. A. Pearce ◽  
S. A. Prahl ◽  
C. R. Denham
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Thermal Properties ◽  
Tissue Blood Flow ◽  
Conductivity Measurements ◽  
Bioheat Equation ◽  
Tissue Conductivity ◽  
Diffusivity Measurements ◽  
Tissue Surface ◽  
Effective Thermal Properties

A microcomputer based instrument to measure effective thermal conductivity and diffusivity at the surface of a tissue has been developed. Self-heated spherical thermistors, partially embedded in an insulator, are used to simultaneously heat tissue and measure the resulting temperature rise. The temperature increase of the thermistor for a given applied power is a function of the combined thermal properties of the insulator, the thermistor, and the tissue. Once the probe is calibrated, the instrument accurately measures the thermal properties of tissue. Conductivity measurements are accurate to 2 percent and diffusivity measurements are accurate to 4 percent. A simplified bioheat equation is used which assumes the effective tissue thermal conductivity is a linear function of perfusion. Since tissue blood flow strongly affects heat transfer, the surface thermistor probe is quite sensitive to perfusion.

Computer Assisted Design of Rubber Mounting Springs

1992 ◽  
Author(s):  
T. E. Shoup ◽  
L. A. Sanchez
Keyword(s):  
Numerical Methods ◽  
Numerical Procedure ◽  
Design Procedure ◽  
Computer Assisted ◽  
Numerical Techniques ◽  
Numerical Approximations ◽  
Design Procedures ◽  
Computer Assisted Design ◽  
First Time ◽  
Digital Computers

Abstract While analysis procedures for the design of rubber mountings have existed for a number of years, the nonlinearity of these useful devices has limited the number of design procedures that are available. This paper presents a design procedure for the static deflections of rubber mountings. It is believed that this is the first time that such numerical procedures have been described in the design literature. The procedures are made possible by a combination of numerical approximations of data in the engineering literature and numerical methods for handling transcendental relationships. Such design procedures would clearly not be possible without the use of the digital computers and the numerical techniques that it facilitates. Design examples are presented to illustrate the use of the numerical procedure.

Boundary Conditions for Symmetry in Bourdon Tubes

1972 ◽  
Vol 94 (1) ◽  
pp. 67-70 ◽  
Author(s):  
R. F. Dressler
Keyword(s):  
Boundary Conditions ◽  
Original Problem ◽  
Shell Theory ◽  
Mathematical Problem ◽  
Order System ◽  
Natural Boundary ◽  
Eighth Order ◽  
Computer Calculations ◽  
Natural Boundary Conditions ◽  
Well Posed

The four natural boundary conditions are derived for a newly observed symmetry in Bourdon tube action. The problem is described by an eighth-order system of pde’s for a Donnell-type shell theory. These, together with boundary conditions for the geometric symmetry and for the free end with rigid plug, comprise a well-posed mathematical problem. It requires only one-fourth the integration domain of the problem posed without symmetry, hence reduces storage requirements in computer calculations to one-sixteenth the number for the original problem.

Simple Numerical Procedure for the Digital Computer Solution of Non-Linear Transient Heat Conduction with Changes of Phase

1966 ◽  
Vol 8 (3) ◽  
pp. 259-263 ◽  
Author(s):  
F. C. Lockwood
Keyword(s):  
Thermal Properties ◽  
Heat Conduction ◽  
Finite Difference ◽  
Numerical Procedure ◽  
Transient Heat Conduction ◽  
Temperature Dependent ◽  
Computer Solution ◽  
Integral Transformations ◽  
Finite Difference Technique ◽  
Explicit Finite Difference

A practical numerical method is described for the solution of transient heat conduction where the thermal properties are temperature dependent and changes of phase occur. The procedure involves the use of the explicit finite difference technique, for which a stability criterion is given, in conjunction with two integral transformations.

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