Additive manufacturing (AM) surfaces offer the possibility of novel cooling channel geometries for high temperature applications. AM processes can optimize the internal geometry of cooling channels, which is generally constrained by limitations of conventional machining processes. The AM process gives rise to surface textures that depend on the build and scan orientations that also potentially contribute to heat-transfer characteristics and provide additional considerations for optimization. The motivation behind this research work is to explore the correlation between AM roughness characteristics (build-orientations, density of spatter deposits and their sizes, amplitudes/wavelengths, etc) and the resulting effect on heat transfer and pressure drop across cooling channels. In this study, the actual AM surfaces with different build angles were fabricated using Laser powder bed fusion (LPBF) and the roughness data of these surfaces were acquired. These measured surface topographies were used for developing simplified surfaces for the purposes of CFD simulations. Modeled AM surfaces with different build orientations were used to analyze the effect of built orientation and spatter deposits in terms of heat transfer for different flow conditions. The CFD simulations also informed the design of the experimental set-up for the validation of computational results. For the comparison, a reference smooth surface is machined from forged Inconel-625 for experiments and CFD simulations were also carried out for the validation. Results from CFD simulations show that the surface features (such as build angles and spatter deposits) significantly affect the heat transfer and fluid flow in terms of Nusselt number and pressure drop and the surface area impact on heat transfer is minimal in all the cases for both laminar and turbulent flow conditions. Under turbulent flow conditions, transverse track alignment shows the highest efficiency in terms of the Nusselt number and adding particles improves heat transfer efficiency for smooth and parallel-tracked surfaces. However, when the flow becomes laminar, reversed behavior is observed and surfaces show downside effects in terms of Nu. Also we define a performance factor that assesses the combined effects of both the thermal and the fluid flow characteristics to differentiate the performance of the AM channels.

中文翻译：

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不同构建方向的增材制造表面的 CFD 和实验研究


增材制造 (AM) 表面为高温应用提供了新颖的冷却通道几何形状的可能性。增材制造工艺可以优化冷却通道的内部几何形状，而这通常受到传统加工工艺的限制。增材制造工艺会产生取决于构建和扫描方向的表面纹理，这些纹理也可能有助于传热特性，并为优化提供额外的考虑因素。这项研究工作的动机是探索增材制造粗糙度特性（构建方向、飞溅沉积物的密度及其尺寸、振幅/波长等）与由此产生的对冷却通道传热和压降的影响之间的相关性。在这项研究中，使用激光粉末床熔合（LPBF）制造了具有不同构建角度的实际增材制造表面，并获取了这些表面的粗糙度数据。这些测量的表面形貌用于开发简化的表面，以进行 CFD 模拟。使用具有不同构建方向的建模增材制造表面来分析构建方向和飞溅沉积物在不同流动条件下的传热方面的影响。 CFD 模拟还为验证计算结果的实验​​装置设计提供了信息。为了进行比较，使用锻造 Inconel-625 加工出参考光滑表面进行实验，并进行 CFD 模拟进行验证。 CFD 模拟的结果表明，表面特征（例如构建角度和飞溅沉积物）在努塞尔数和压降方面显着影响传热和流体流动，并且在所有情况下，表面积对传热的影响都很小层流和湍流条件。在湍流条件下，横向轨道排列在努塞尔数方面表现出最高的效率，并且添加颗粒可提高光滑和平行轨道表面的传热效率。然而，当流动变成层流时，会观察到相反的行为，并且表面在 Nu 方面显示出负面影响。此外，我们还定义了一个性能因子，用于评估热特性和流体流动特性的综合影响，以区分 AM 通道的性能。