scholarly journals Sensitivity analysis of temperature in heated soft tissues with respect to time delays

2021 ◽  
Author(s):  
E. Majchrzak ◽  
G. Kałuża
Keyword(s):  
Heat Flux ◽  
Sensitivity Analysis ◽  
Soft Tissues ◽  
Initial Conditions ◽  
External Heat ◽  
Phase Lag ◽  
Thermalization Time ◽  
Temperature Changes ◽  
Tissue Region ◽  
External Heat Flux

AbstractAxisymmetric tissue region heated by an external heat flux is considered. The mathematical model is based on the dual-phase lag equation supplemented by appropriate boundary and initial conditions. This equation, in relation to the Pennes’ equation, has two additional parameters, namely the relaxation time and the thermalization time. The aim of this research is to estimate the temperature changes due to changes of these parameters. To achieve this, sensitivity analysis methods are used. The basic problem and additional ones related to the sensitivity functions are solved using the implicit scheme of the finite difference method. The performed computations show that the temperature changes caused by changes in the relaxation and thermalization times are larger for higher values of the external heat flux and shorter times of its action.

Modeling of Laser-Soft Tissue Interactions Using the Dual-Phase Lag Equation: Sensitivity Analysis with Respect to Selected Tissue Parameters

2017 ◽  
Vol 379 ◽  
pp. 108-123
Author(s):  
Ewa Majchrzak ◽  
Marek Jasiński ◽  
Łukasz Turchan
Keyword(s):  
Sensitivity Analysis ◽  
Soft Tissue ◽  
Laser Irradiation ◽  
Soft Tissues ◽  
Initial Conditions ◽  
Internal Heat ◽  
Bioheat Transfer ◽  
Phase Lag ◽  
Dual Phase ◽  
Coupled Equations

Thermal processes occurring in soft tissues are subjected to laser irradiation are analyzed. The transient bioheat transfer is described by the generalized dual-phase lag model. This model consists of two coupled equations concerning the tissue and blood temperatures supplemented by the appropriate boundary and initial conditions. The efficiency of the internal heat source connected to the laser irradiation results from the solution of the diffusion equation. This approach is acceptable when the scattering dominates over the absorption for wavelengths between 650 and 1300 nm, and just such a situation occurs in the case of soft tissues. Sensitivity analysis with respect to the parameters occurring in the mathematical model is done using the direct approach (differentiation of the basic equations and the boundary-initial conditions with respect to the parameter considered), especially the absorption coefficient and scattering coefficient of the soft tissue are considered. At the stage of numerical modeling the basic problem and additional problems connected with the sensitivity functions are solved using the finite difference method. In the final part the conclusions and examples of computations are presented.

The Application of IRAs Optimizing Design in Vacuum Thermal Test

2013 ◽  
Vol 390 ◽  
pp. 708-713
Author(s):  
Yu Wei Sun ◽  
Xiao Ning Yang
Keyword(s):  
Heat Flux ◽  
Heated Surface ◽  
Design Guidelines ◽  
External Heat ◽  
Simulation Test ◽  
Thermal Tests ◽  
Typical Structure ◽  
Infra Red ◽  
Optimizing Design ◽  
External Heat Flux

The thermal vacuum environment simulation test is indispensible for the development of spacecrafts. And the simulation of the external heat flux exerted onto the spacecraft is one of the determining elements of the simulation test. In China, the infra-red simulation is a common method that used as simulation equipment of the external heat flux. The planar infra-red arrays is the most typical structure elements for planar spacecraft surface, but the margin effect of infra-red arrays influences the flux uniformity on heated surface severely. Based on Monte Carlo theory, some optimizing design guidelines had been drawn about planar infra-red arrays in past investigation. This paper introduces some testing and experiment that could confirm these guidelines, and these guidelines had been applied in some vacuum thermal tests of spacecrafts successfully.

Experimental study of commercial flame-retardant polycarbonate under external heat flux

2017 ◽  
Vol 131 (2) ◽  
pp. 1463-1470 ◽  
Author(s):  
Xuelin Zhang ◽  
Teng Zhang ◽  
Changhai Li ◽  
Hongshuang Wang ◽  
Xiao Chen ◽  
...  
Keyword(s):  
Experimental Study ◽  
Heat Flux ◽  
Flame Retardant ◽  
External Heat ◽  
External Heat Flux

Effectiveness-NTU Relationship for a Counterflow Heat Exchanger Subjected to an External Heat Transfer

2004 ◽  
Vol 127 (9) ◽  
pp. 1071-1073 ◽  
Author(s):  
Gregory F. Nellis ◽  
John M. Pfotenhauer
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Exchanger ◽  
Numerical Model ◽  
Analytical Solution ◽  
Convenient Method ◽  
Process Engineering ◽  
External Heat ◽  
External Heat Transfer ◽  
External Heat Flux

This paper presents the analytical solution for the effectiveness of a counterflow heat exchanger subjected to a uniformly distributed, external heat flux. The solution is verified against conventional ε-NTU relations in the limit of zero external heat flux. This situation is of interest in applications such as cryogenic and process engineering, and the analytical solution provides a convenient method for treating differential elements of a heat exchanger in a numerical model.

scholarly journals Initiation Parameters of Granulated Synthetic Polymers

2021 ◽  
Vol 29 (48) ◽  
pp. 114-122
Author(s):  
Peter Rantuch ◽  
Jozef Martinka ◽  
Tomáš Štefko ◽  
Igor Wachter
Keyword(s):  
Heat Flux ◽  
Polymeric Materials ◽  
Synthetic Polymers ◽  
Flow Time ◽  
External Heat ◽  
Small Thickness ◽  
Gaseous Products ◽  
Product Method ◽  
Different Shapes ◽  
External Heat Flux

Abstract Polymeric materials, which are currently very often used in various industries, are often transported and stored in the form of granules before processing. This method has several advantages, but in most studies the test samples are modified to different shapes and dimensions. This paper is therefore focused on the initiation of selected granular plastics. Samples of five polymeric materials were exposed to an external heat flux from 20 kW.m−2 to 40 kW.m−2. A spark initiator was used to ignite the released gaseous products of thermal decomposition of the polymer sample. FTP (flow-time product) method was applied to the obtained parameter - time to ignition, from which other initiation parameters were determined. The critical heat flux was determined in the range of 5.0 kW.m−2 - 11.8 kW.m−2. Despite the relatively small thickness (4 mm), the samples behaved as thermally thick. During the measurement, thin surface layer melted, and the rest of the polymer remained in its original granulated form. Ignition temperatures were calculated according to the Stefan-Boltzmann’s law between 273 °C - 402 °C.

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