IMPACT OF MEASUREMENTS TECHNIQUES ON HEAT TRANSFER CHARACTERISTICS IN AIR JET ARRAYS

Assim Hameed Yousif Al Daraje, Afrah Awad, Mohamed Gogazeh, Hanan Afeef Mohammad Khamees
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Abstract

Air impact processes have diverse applications in engineering, including backflow welding, textile drying, and gas turbine blade and combustion liner cooling. This research examines the influence of experimental methodologies and measurement tools on convective heat transfer in adjustable air jet assemblies. The experiment involves the use of heated targets made of thin stainless steel foil with constant heat flux boundary conditions. Thermography measures target surface temperatures by analyzing how internal passage cross-flow affects convective heat transfer via outflow adjustments. The experiments involve two arrays of jet nozzles: inline and staggering, each comprising 44 impingement jet nozzles arranged in 4 rows with 11 jet holes in each row. The study presents unsteady time average local and spatial Nusselt numbers as functions of jet Reynolds number (4630-14000) and explores their dependence on the jet nozzle diameter. Cross-flow levels significantly affect spatial and local Nusselt numbers in both local and span-wise averaged values, regardless of the Reynolds number. Strong cross-flow (single configuration) distributes flow causing turbulence and uneven heat distribution, reducing Nusselt numbers. In contrast, moderate cross-flow (double configuration) improves heat transfer and increases Nusselt numbers. The study emphasizes the crucial role of experimental techniques in heat transfer evaluation and demonstrates agreement with prior studies within a standard error below 5%.
测量技术对空气喷射阵列传热特性的影响
空气冲击过程在工程领域有多种应用,包括回流焊接、纺织品干燥以及燃气轮机叶片和燃烧衬垫冷却。本研究探讨了实验方法和测量工具对可调空气喷射组件中对流传热的影响。实验中使用了由薄不锈钢箔制成的加热目标,其边界条件为恒定热通量。热成像技术通过分析内部通道横流如何通过流出调节影响对流传热来测量目标表面温度。实验涉及两个喷射喷嘴阵列:直列式和交错式,每个阵列由 44 个撞击式喷射喷嘴组成,每排 11 个喷射孔,按 4 行排列。研究以射流雷诺数(4630-14000)的函数形式呈现了非稳定时间平均局部和空间努塞尔特数,并探讨了它们与射流喷嘴直径的关系。无论雷诺数如何,横流水平都会对局部和跨度平均值的空间和局部努塞尔特数产生重大影响。强横流(单一配置)会使流体分布造成湍流和热量分布不均,从而降低努塞尔特数。与此相反,适度的交叉流(双配置)改善了传热,提高了努塞尔特数。该研究强调了实验技术在传热评估中的关键作用,并证明了与之前研究的一致性,标准误差低于 5%。
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来源期刊
CiteScore
0.70
自引率
0.00%
发文量
74
审稿时长
50 weeks
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