Anisotropic Thermal Conductivity of Nanoporous Silica Film

2004 ◽  
Vol 51 (1) ◽  
pp. 20-27 ◽  
Author(s):  
B.-Y. Tsui ◽  
C.-C. Yang ◽  
K.-L. Fang
RSC Advances ◽  
2021 ◽  
Vol 11 (39) ◽  
pp. 24456-24465
Author(s):  
Rapaka S. C. Bose ◽  
K. Ramesh

Polycrystalline p-type Sb1.5Bi0.5Te3 (SBT) and n-type Bi2Te2.7Se0.3 (BTS) compounds possessing layered crystal structure show anisotropic electronic and thermal transport properties.


Author(s):  
Carol Bryant ◽  
James L. Rutledge

Abstract Increasing interest in the use of ceramic matrix composites (CMCs) for gas turbine engine hot gas path components requires a thorough examination of the thermal behavior one may expect of such components. Their highly anisotropic thermal conductivity is a substantial departure from traditional metallic components and can influence the temperature distribution in surprising ways. With the ultimate surface temperature dependent upon the internal cooling scheme, including cooling from within the film cooling holes themselves, as well as the external film cooling, the relative influence of these contributions to cooling can be affected by the directionality of the thermal conductivity. Conjugate heat transfer computational simulations were performed to evaluate the effect of anisotropy in the leading edge region of a turbine component. The leading edge region is modeled as a fully film-cooled half cylinder with a flat afterbody. The anisotropic directionality of the thermal conductivity is shown to have a significant effect on the temperature distribution over the surface of the leading edge. While structural considerations with CMC components are often paramount, designers should be aware of the thermal ramifications associated with the selection of the CMC layup.


Author(s):  
Carol E. Bryant ◽  
James L. Rutledge

Abstract Ceramic matrix composites (CMCs) show promise as higher temperature capable alternatives to traditional metallic components in gas turbine engine hot gas paths. However, CMC components will still require both internal and external cooling, such as film cooling. The overall cooling effectiveness is determined not only by the design of coolant flow, but also by the conduction through the materiel itself. CMCs have anisotropic thermal conductivity, giving rise to heat flow that differs somewhat relative to what we have come to expect from experience with traditional metallic components. Conjugate heat transfer computational fluid dynamics (CFD) simulations were performed in order to isolate the effect anisotropic thermal conductivity has on a cooling architecture consisting of both internal and external cooling. Results show the specific locations and unique effects of anisotropic thermal conduction on overall effectiveness. Thermal conductivity anisotropy is shown to have a significant effect on the resulting overall effectiveness. As CMCs begin to make their way into gas turbine engines, care must be taken to ensure that anisotropy is characterized properly and considered in the thermal analysis.


2000 ◽  
Author(s):  
Theodorian Borca-Tasciuc ◽  
Weili Liu ◽  
Jianlin Liu ◽  
Kang L. Wang ◽  
Gang Chen

Abstract In this work, we present experimental results on the in-plane and cross-plane thermal conductivity characterization of a Si/Ge quantum-dots superlattice structure. The quantum-dots superlattice was grown by molecular-beam-epitaxy and self-organization. The anisotropic thermal conductivity measurements are performed by a differential two-wire 3ω method. The measured in-plane and cross-plane thermal conductivity values show a different temperature behavior. The results are compared and explained with heat transport models in superlattices.


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