Browsing by Author "Lor, WB"

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Effect of interface thermal resistance on heat transfer in a composite medium using the thermal wave model
(2000-03-01)
Lor, WB
;
Chu, HS
;
機械工程學系
;
Department of Mechanical Engineering
This study analyzes how interface resistance affects heat transfer in a two-layered composite media under an incident pulse energy exerting on the exterior surface of one layer by using the hyperbolic heat conduction equation. The incident energy is absorbed and a pulse width temperature wave is generated within the skin depth of the first layer, which subsequently emanates to the second layer. Reflection and transmission occur when the initial pulse wave impacts the contact surface of the dissimilar material. In addition, the radiation-boundary-condition model based on Acoustic Mismatch Model or Diffuse Mismatch Model is used to predict the interface resistance. Analysis results indicate that the reflection-transmission combination phenomena strongly depend on the interface condition. Moreover, the thermal resistance restricts the energy transmission across the interface, creating a temperature difference at the interface and ultimately alerting the reflected wave feature. Our results further demonstrate that the critical thermal resistance magnitude to approach the perfect contact condition varies with the two-layered properties ratio and the absorption skin depth. (C) 1999 Elsevier Science Ltd. All rights reserved.
Effect of interface thermal resistance on thermal wave phenomena in a two-layer composite media
(1999)
Lor, WB
;
Chu, HS
;
機械工程學系
;
Department of Mechanical Engineering
This article numerically analyzes the heat conduction in a two layers composite media under an initial temperature pulse emanating from the exterior surface of one layer. The thermal wave model, which allows for both a transient heat flux and a finite speed of propagation, predicts significantly different results with those predicted by the Fourier's diffusion model at small time scale. The differences between the two heat transfer models diminish with increasing time. The thermal wave model further demonstrates that the internal reflection and transmission occur at the contact surface of the dissimilar material. To consider the thermal resistance at the contact interface, an interfacial-layer model (ILM) and a radiation heat flux model at the interface based on acoustic mismatch model (AMM) or diffuse mismatch model (DMM) are employed. Analysis results indicate that the thermal boundary resistance significantly influences the wave pattern and strength. The reflection-transmission-combination phenomena strongly varies with the two layers properties ratio, skin depth, and the interface condition.
Hyperbolic heat conduction in thin-film high T-c superconductors with interface thermal resistance
(1999-09-01)
Lor, WB
;
Chu, HS
;
機械工程學系
;
Department of Mechanical Engineering
This article numerically analyzes the hyperbolic heat conduction problem in the film and substrate composites under an imposed surface heat flux on the exterior film surface. The radiation heat flux model is employed to take account of the interface thermal resistance. The reflection and transmission occur at the contact surface of the dissimilar material which depends on the substrate properties and interface conditions. The interface resistance restricts the energy transmission across the interface and alerts the reflected and transmitted waves' strength. Neglecting the interface thermal resistance causes the temperature distribution in the film to be greatly underestimated. Moreover, the hyperbolic equation predicts significantly different results with those predicted by the parabolic equation at small time scales. The discrepancies between the solutions in an investigation of superconductor Y-Ba-Cu-O film depositions on several commonly used substrates are examined. (C) 1999 Elsevier Science Ltd. All rights reserved.
Propagation of thermal waves in a composite medium with interface thermal boundary resistance
(1999-11-26)
Lor, WB
;
Chu, HS
;
機械工程學系
;
Department of Mechanical Engineering
This article numerically analyzes the hyperbolic heat conduction problem in a two-layer composite medium under an initial temperature pulse emanating from the exterior surface of one layer. Reflection and transmission occur when the initial pulse wave impacts the contact surface of the dissimilar material. An interfacial layer with low conductivity and narrow thickness exists at the interface, which is employed to model the thermal boundary resistance at the contact surface, Analysis results indicate Bat the interface resistance significantly influences the wave pattern and strength. The presentation of the wave nature in Be interfacial layer deforms the initial ware feature and induces secondary wavelets behind the reflected and transmitted wave. In addition, the piecewise secondary wavelets become smooth when the interfacial width is very thin. Also examined herein is the effect of conductivity and thickness width of the interfacial layer coupled with variation of Be two-layer properties ratio on the reflection-transmission-combination phenomena.