Transverse rarefaction of a layer behind the front of a longitudinal wave of nonlinear thermal conductivity and features of plasma formation inside the target cavity

1999 ◽  
Vol 19 (6) ◽  
pp. 581-600
Author(s):  
S. Yu. Gus’kov ◽  
I. Ya. Doskach
Keyword(s):  
Thermal Conductivity ◽  
Longitudinal Wave ◽  
Plasma Formation ◽  
Nonlinear Thermal Conductivity

Adaptive Thermal Conductivity Metamaterials: Enabling Active and Passive Thermal Control

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
Austin A. Phoenix ◽  
Evan Wilson
Keyword(s):  
Thermal Conductivity ◽  
Thermal Management ◽  
Passive Control ◽  
Coefficient Of Thermal Expansion ◽  
Thermal Strain ◽  
Thermal Control ◽  
Variable Thermal Conductivity ◽  
Highly Nonlinear ◽  
Wide Range ◽  
Nonlinear Thermal Conductivity

The novel adaptive thermal metamaterial developed in this paper provides a unique thermal management capability that can address the needs of future spacecraft. While advances in metamaterials have provided the ability to generate materials with a broad range of material properties, relatively little advancement has been made in the development of adaptive metamaterials. This metamaterial concept enables the development of materials with a highly nonlinear thermal conductivity as a function of temperature. Through enabling active or passive control of the metamaterials bulk effective thermal conductivity, this metamaterial that can improve the spacecraft's thermal management systems performance. This variable thermal conductivity is achieved through induced contact that results in changes in the F path length and the conductive path area. The contact can be generated internally using thermal strain from shape memory alloys, bimetal springs, and mismatches in coefficient of thermal expansion (CTE) or it can be generated externally using applied mechanical loading. The metamaterial can actively control the temperature of an interface by dynamically changing the bulk thermal conductivity controlling the instantaneous heat flux through the metamaterial. The design of thermal stability regions (regions of constant thermal conductivity versus temperature) into the nonlinear thermal conductivity as a function of temperature can provide passive thermal control. While this concept can be used in a wide range of applications, this paper focuses on the development of a metamaterial that achieves highly nonlinear thermal conductivity as a function of temperature to enable passive thermal control of spacecraft systems on orbit.

scholarly journals Nonlinear thermal conductivity in gases

2016 ◽  
Vol 57 ◽  
Author(s):  
Arvydas Juozapas Janavičius ◽  
Sigita Turskienė
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Nonlinear Equation ◽  
Diffusion Processes ◽  
Finite Velocity ◽  
Practical Applications ◽  
Different Temperatures ◽  
Gas Molecules ◽  
Diffusivity Equation ◽  
Nonlinear Thermal Conductivity

The nonlinear diffusion equation corresponds to the diffusion processes which can occur with a finite velocity. A.J. Janavičius proposed nonlinear equation which describes more exactly the diffusion of impurities in Si crystals in many interesting practical applications. The heat transfer in gases is also based on diffusion of gas molecules from hot regions to the coldest ones with a finite velocity by random Brownian motions. In this case the heat transfer can be considered using similar nonlinear thermal diffusivity equation. The approximate analytical solution of this nonlinear equation can be used for the experimental analysis of thermal conductivity coefficients using temperature profiles dependence on different temperatures and pressures in gases.  

scholarly journals On the New Nonlinear Properties of the Nonlinear Heat Conductivity Problem

2019 ◽  
Vol 9 (1) ◽  
pp. 1542-1543
Keyword(s):  
Thermal Conductivity ◽  
Exact Analytical Solution ◽  
Thermal Structure ◽  
Nonlinear Effects ◽  
Spatial Localization ◽  
Thermal Processes ◽  
Nonlinear Media ◽  
Nonlinear Properties ◽  
Characteristic Features ◽  
Nonlinear Thermal Conductivity

In this article, we discuss one problem of nonlinear thermal conductivity with double nonlinearity; an exact analytical solution has been found for it, the analysis of which allows revealing a number of characteristic features of thermal processes in nonlinear media. The following nonlinear effects have been established: the inertial effect, the finite propagation velocity of thermal disturbances, the spatial localization of heat, and the effect of the finite time of the existence of a thermal structure in an absorption medium.

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