Thermal Rectification Under Transient Conditions: The Role of Thermal Capacitance and Thermal Conductivity

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Francisco A. Herrera ◽  
Tengfei Luo ◽  
David B. Go
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Temperature Dependent ◽  
Unusual Behavior ◽  
Transient Conditions ◽  
Thermal Rectification ◽  
Practical Applications ◽  
Thermal Capacitance ◽  
Temperature Dependent Thermal Conductivity

A thermal rectifier transmits heat asymmetrically, transmitting heat in one direction and acting as an insulator in the opposite direction. For conduction at steady-state, thermal rectification can occur naturally in systems where the thermal conductivity of the material(s) varies in space and with temperature. However, in practical applications, rectification may often need to be controlled or understood under transient conditions. Using a bulk composite, specifically a two-slab composite, as a model system, we analyze transient rectifying behavior. We find that under some conditions transient rectification can be several times larger than steady-state rectification. Further, both the thermal diffusivity of the system and the temperature-dependent thermal conductivity or thermal capacitance play an important role in affecting the transient rectifying behavior of the system, with the nonlinearity of the system leading to unusual behavior where rectification is maximized.

scholarly journals A Linear Approach Suitable for a Class of Steady-State Heat Transfer Problems with Temperature-Dependent Thermal Conductivity

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
R. M. S. Gama ◽  
R. Pazetto
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Steady State ◽  
Robin Boundary Conditions ◽  
Temperature Dependent ◽  
Steady State Heat ◽  
Steady State Heat Transfer ◽  
Transfer Problems ◽  
Robin Boundary ◽  
Temperature Dependent Thermal Conductivity

This work presents an useful tool for constructing the solution of steady-state heat transfer problems, with temperature-dependent thermal conductivity, by means of the solution of Poisson equations. Specifically, it will be presented a procedure for constructing the solution of a nonlinear second-order partial differential equation, subjected to Robin boundary conditions, by means of a sequence whose elements are obtained from the solution of very simple linear partial differential equations, also subjected to Robin boundary conditions. In addition, an a priori upper bound estimate for the solution is presented too. Some examples, involving temperature-dependent thermal conductivity, are presented, illustrating the use of numerical approximations.

Role of Collective and Localized Modes on the Temperature-Dependent Thermal Conductivity in Polycrystalline C60 Fullerite Compacts

1997 ◽  
Vol 11 (23) ◽  
pp. 1031-1035 ◽  
Author(s):  
S. P. Tewari ◽  
Poonam Silotia ◽  
Kakoli Bera
Keyword(s):  
Thermal Conductivity ◽  
Relaxation Times ◽  
Collective Modes ◽  
Total Thermal Conductivity ◽  
Phonon Modes ◽  
Temperature Dependent ◽  
Localized Modes ◽  
Diffusive Modes ◽  
Temperature Dependent Thermal Conductivity

Recently observed thermal conductivity of polycrystalline C 60 fullerite compacts has been explained on the basis of a suggested dynamical model of the fullerites which takes into account the collective acoustic phonon modes with frequency dependent relaxation time and localized libronic and orientational diffusive modes with constant relaxation times, in the temperature range 0.7–300 K. Though the bulk of the conduction is via collective modes, the localized modes, too, contribute significantly to the total thermal conductivity.

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