Experimental Evidence of the Thermal Cloak Based on the Path Design of the Heat Flux

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
Xiao He ◽  
Tianzhi Yang ◽  
Linzhi Wu
Keyword(s):  
Heat Flux ◽  
Experimental Evidence ◽  
Thermal Protection ◽  
Large Degree ◽  
New Method ◽  
Material Parameters ◽  
Path Design ◽  
New Strategy ◽  
Transient Thermal ◽  
Blue Print

We recently showed theoretically that the infinite singularity of the thermal cloak designed by transformation thermodynamics could be eliminated by a new method—the path design of the heat flux without any approximation. In this paper, we present the experimental evidence of such a new strategy of thermal cloak, that is, a truly singularity-free thermal cloak. We fabricate such a transient thermal cloak device without using extreme material parameters. The experimental results show fully controlled, transient cloaking behavior, which are perfectly consistent with the theoretical derivations and simulated results. Since one can flexibly design the path of heat flux in the cloak, it has the large degree-of-freedom to construct thermal cloaks with the specific distributions of material parameters. The new method provides a new blue print for the transient thermal protection of a specific target.

Cylindrical Thermal Cloak Based on the Path Design of Heat Flux

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Linzhi Wu
Keyword(s):  
Heat Flux ◽  
Thermal Protection ◽  
Transient Behavior ◽  
Large Degree ◽  
Comsol Multiphysics ◽  
Material Parameters ◽  
Path Design ◽  
Transient Thermal ◽  
Blue Print ◽  
Dynamic Diffusion

When heat flux flows in a given medium, its path will solely be determined. This implies that material parameters determined by the predesigned path of heat flux will guide heat to flow along the designed path. Based on this idea, we develop a new method for the design of the cylindrical thermal cloak which can make heat flux detour the cloaked object. For the inhomogeneous anisotropic medium, we derive the relation between the path trajectory of heat flux and material parameters and obtain two differential equations and one boundary condition which are used to determine material parameters in the cylindrical cloak. The transient behavior on the flow of heat flux is simulated by Comsol Multiphysics and the transient thermal protection of the cylindrical cloak for the cloaked object is examined. The effect of the product of density and specific heat on the dynamic diffusion process of heat flux is analyzed. Since one can flexibly design the path of heat flux in the cloak, it has the large degree of freedom to construct thermal cloaks with the specific distributions of material parameters. The present method provides a new blue print for the transient thermal protection of a specific target.

scholarly journals Effects of operating and material parameters on the thermal characteristics of a wet clutch

2021 ◽  
Vol 13 (7) ◽  
pp. 168781402110341
Author(s):  
Zhigang Zhang ◽  
Ling Zou ◽  
Hang Liu ◽  
Yonglong Chen ◽  
Benzhu Zhang
Keyword(s):  
Heat Flux ◽  
Applied Pressure ◽  
Thermal Characteristics ◽  
Thermal Models ◽  
Material Parameters ◽  
Heat Transfer Theory ◽  
Friction Disk ◽  
Viscous Shear ◽  
Wet Clutch ◽  
Transient Thermal

Based on the frictional mechanism of a wet clutch, frictional models of wet clutch engagement were established using the modified Reynolds equation and the elastic contact model between frictional pairs. Then, the heat flux models for the viscous shear and asperity friction were built, and the two-dimensional transient thermal models for the separator plate, friction disk, and ATF heat convection model were deduced based on the heat transfer theory and conservation law of energy. Finally, the Runge–Kutta numerical method was used to solve the frictional and thermal models. The average temperature of the separator plate, friction disk, and ATF were calculated. The effects of operating and material parameters, such as applied pressure, initial angular velocity, friction lining permeability, surface combined roughness RMS, equivalent elastic modulus, and ATF flow, on the thermal characteristics of friction pairs and ATF during engagement, were studied. The simulation results show that the temperature characteristics of the separator plate, friction disk, and ATF depend mainly on the viscous shear and asperity friction heat flux, and that the operating and material parameters of the wet clutch also have significant impacts on the overall variation trend of the thermal characteristics of the separator plate, friction disk, and ATF.

scholarly journals A Parametrical Study on Convective Heat Transfer between High-Temperature Gas and Regenerative Cooling Panel

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1784
Author(s):  
Jiangyu Hu ◽  
Ning Wang ◽  
Jin Zhou ◽  
Yu Pan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
High Temperature ◽  
Thermal Protection ◽  
Flow Direction ◽  
Heated Surface ◽  
Heat Transfer Process ◽  
Cocurrent Flow ◽  
Regenerative Cooling ◽  
High Temperature Gas

Thermal protection is still one of the key challenges for successful scramjet operations. In this study, the three-dimensional coupled heat transfer between high-temperature gas and regenerative cooling panel with kerosene of supercritical pressure flowing in the cooling channels was numerically investigated to reveal the fundamental characteristics of regenerative cooling as well as its influencing factors. The SST k-ω turbulence model with low-Reynolds-number correction provided by the pressure-based solver of Fluent 19.2 is adopted for simulation. It was found that the heat flux of the gas heated surface is in the order of 106 W/m2, and it declines along the flow direction of gas due to the development of boundary layer. Compared with cocurrent flow, the temperature peak of the gas heated surface in counter flow is much higher. The temperature and heat flux of the gas heated surface both rises with the static pressure and total temperature of gas. The heat flux of the gas heated surface increases with the mass flow rate of kerosene, and it hardly changes with the pressure of kerosene. Results herein could help to understand the real heat transfer process of regenerative cooling and guide the design of thermal protection systems.

scholarly journals Method Development for Estimating Sensible Heat Flux over the Tibetan Plateau from CMA Data

2009 ◽  
Vol 48 (12) ◽  
pp. 2474-2486 ◽  
Author(s):  
Kun Yang ◽  
Jun Qin ◽  
Xiaofeng Guo ◽  
Degang Zhou ◽  
Yaoming Ma
Keyword(s):  
Heat Flux ◽  
Tibetan Plateau ◽  
Method Development ◽  
Sensible Heat Flux ◽  
Atmospheric Stability ◽  
Surface Energy Budget ◽  
New Method ◽  
The Tibetan Plateau ◽  
Sensible Heat ◽  
Hourly Data

Abstract To clarify the thermal forcing of the Tibetan Plateau, long-term coarse-temporal-resolution data from the China Meteorological Administration have been widely used to estimate surface sensible heat flux by bulk methods in many previous studies; however, these estimates have seldom been evaluated against observations. This study at first evaluates three widely used bulk schemes against Tibet instrumental flux data. The evaluation shows that large uncertainties exist in the heat flux estimated by these schemes; in particular, upward heat fluxes in winter may be significantly underestimated, because diurnal variations of atmospheric stability were not taken into account. To improve the estimate, a new method is developed to disaggregate coarse-resolution meteorological data to hourly according to statistical relationships derived from high-resolution experimental data, and then sensible heat flux is estimated from the hourly data by a well-validated flux scheme. Evaluations against heat flux observations in summer and against net radiation observations in winter indicate that the new method performs much better than previous schemes, and therefore it provides a robust basis for quantifying the Tibetan surface energy budget.

New strength metrics for containerboards: influences of basic papermaking factors

2018 ◽  
Vol 33 (4) ◽  
pp. 592-602
Author(s):  
Amanda Mattsson ◽  
Tetsu Uesaka
Keyword(s):  
Time Dependent ◽  
New Method ◽  
Creep Tests ◽  
Material Parameters ◽  
Dependent Failures ◽  
Short Term Strength ◽  
New Material ◽  
End Use ◽  
Future Work ◽  
Operating Window

Abstract In end-use, containerboard is subjected to a variety of loading histories, such as seconds of loading/unloading, hours of vibration, days of creep load. The fundamental question is whether the commonly measured static strength represents “strength” under these conditions. Another question is, since those time-dependent failures are notoriously variable, how to describe the probabilistic aspect. This study concerns the characterisation of these different facets of “strength”. In our earlier work, we have investigated the theoretical framework for time-dependent, probabilistic failures, and identified three material parameters: (1) characteristic strength, {S_{c}}, representing short-term strength, (2) brittleness/durability parameter, ρ, and (3) reliability parameter, β. We have also developed a new method that allows us to determine all these parameters much faster than typical creep tests. Using the new method, we have started investigating effects of basic papermaking variables on the new material parameters. Among the samples tested, the parameter ρ varied from 20 to 50, and β from 0.5 to 1.0. This suggests that, even within the current papermaking practice, there is a wide operating window to tune these new material parameters. The future work is, therefore, to find specific manufacturing variables that can systematically change these new material parameters.

Heat Flux Measurement Method of Two-Phase Flow in SRM

2012 ◽  
Vol 152-154 ◽  
pp. 883-888
Author(s):  
Xiang Yu Zhang ◽  
Guo Qiang He ◽  
Pei Jin Liu ◽  
Jiang Li
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Two Phase Flow ◽  
Thermal Protection ◽  
Flux Measurement ◽  
Combustion Products ◽  
Phase Flow ◽  
Solid Rocket Motor ◽  
Two Phase ◽  
Heat Flux Measurement

Accurate information on heat transfer data of combustion products in the solid rocket motor chamber is a crucial prerequisite for the engine thermal protection. A measurement technique was well developed to acquire steady-state heat flux data of two-phase flow and was used successfully in the hostile environment. Experimental heat flux measurement has been obtained with an innovative designed instrument by simulating the flow field of complex charging configuration. The total heat flux of combustion products in the chamber was brought away by the coolant and calculated by its enthalpy rise in this device. The data could be used to analyze the heat transfer phenomena in SRMs and provide boundary condition for establishing insulation erosion model.

New method for evaluating the kinetic constant of thermal protection materials

2013 ◽  
Vol 27 (6) ◽  
pp. 1713-1719
Author(s):  
Ji-Yeul Bae ◽  
Jong Ju Yi ◽  
Sulki Park ◽  
Ju Chan Bae ◽  
Heecheol Ham ◽  
...  
Keyword(s):  
Thermal Protection ◽  
Kinetic Constant ◽  
New Method

scholarly journals Numerical Study Of Thermal Behavior Of Anisotropic Medium In Bidirectional Cylindrical Geometry

2019 ◽  
Vol 286 ◽  
pp. 08009
Author(s):  
Rabiâ Idmoussa ◽  
Nisrine Hanchi ◽  
Hamza Hamza ◽  
Jawad Lahjomri ◽  
Abdelaziz Oubarra
Keyword(s):  
Heat Flux ◽  
Heat Conduction ◽  
Thermal Behavior ◽  
Anisotropic Medium ◽  
Numerical Study ◽  
Heat Conduction Problem ◽  
Inverse Transformation ◽  
Complicated Geometry ◽  
Alternating Directions Method ◽  
Transient Thermal

In this work, we investigate the transient thermal analysis of two-dimensional cylindrical anisotropic medium subjected to a prescribed temperature at the two end sections and to a heat flux over the whole lateral surface. Due to the complexity of analytically solving the anisotropic heat conduction equation, a numerical solution has been developed. It is based on a coordinate transformation that reduces the anisotropic cylinder heat conduction problem to an equivalent isotropic one, without complicating the boundary conditions but with a more complicated geometry. The equation of heat conduction for this virtual medium is solved by the alternating directions method. The inverse transformation makes it possible to determine the thermal behavior of the anisotropic medium as a function of study parameters: diagonal and cross thermal conductivities, heat flux.

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