Ozge ALTUN, Y. Erhan BOKE, Soner ALANYALI

Numerical modeling of thermal conductivity of air-plasma-sprayed zirconia with different porosity levels

Gözenekli seramik kaplamanın efektif ısı iletim katsayısı gözeneklilik oranına ve gözeneklerin dağılımına bağlıolarak değişmektedir. Bu nedenle ısı transferi çözümlemelerinde gerçek mikroyapının kullanılması önemli bir roloynamaktadır. Bu çalışmada gerçek mikroyapı resimleri kullanılarak atmosferik plasma spray (APS) kaplamanınefektif ısı iletim katsayısı CFD modeli ile literatürde bulunan Maxwell-Eucken ve EMT analitik ifadeleri kullanılarakhesaplanmıştır. CFD modellemeleri Fluent 6.1.22 kodu kullanılarak yapılmıştır. Numuneler kaplama parametrelerinindeğiştirilmesi ile beş farklı gözeneklilikte elde edilmiştir. Numunelerin gözenekliliği 9% - 31% arasındadeğişmektedir. Analitik ve sonlu hacimler metodundan elde edilen ısı iletim katsayısı değerleri literatürde yer alandeneysel sonuçlar ile karşılaştırılmıştır. Nümerik olarak elde edilen efektif ısı iletim katsayısı değerleri deneyselçalışmalar ile uyum sağlamaktadır. Bu çalışma gözenekli seramik malzemenin efektif ısı iletim katsayısının gerçekmikroyapı resimlerinin kullanılarak elde edilmesinde CFD analizinin kullanılabileceğini göstermektedir. Bu sayede,bu model yüksek maliyetli ve zaman alıcı deneylerden önce ön değer elde etmek amacıyla kullanılabilir.

Faklı gözeneklilik oranlarındaki atmosferik plazma spray zirkonyanın ısı iletim katsayısının nümerik modellemesi

The effective thermal conductivity of a porous ceramic coating depends on porosity and the distribution ofpores. Due to these aspects, the structure of a ceramic coating plays an important role in the analysis of heat transfer.In this study, using real microstructural images, effective thermal conductivities of air plasma sprayed (APS) zirconiacoatings have been calculated via CFD modeling as well as using Maxwell-Eucken and the EMT models. CFDstudies were carried out using FLUENT 6.1.22 code. Samples were produced having five different porosities bychanging the coating parameters. The porosities of the samples were in the interval of 9% - 31%. Results obtainedfrom analytical and finite volume methods have been compared to experimental thermal conductivity data given inthe literature. The numerically calculated effective thermal conductivities are in good agreement with thosedetermined experimentally. This study demonstrates that CFD analysis can be used to predict the effective thermalconductivity of porous ceramic coatings using real digital images. By virtue of this, the model can be used to obtainpreliminary values instead of high cost and time-consuming experiments.

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