一种增强型旋流和环形喷射冲击加热平板及其传热特性
An augmented swirling and round jet impinging on a heated flat plate and its heat transfer characteristics
AI总结：
本文提出了一种增强旋流环形喷射的几何机制，通过不同分割比研究其传热特性，发现优化距离和分割比可显著提升传热效率。
摘要：
本文提出了一种生成增强旋流和环形喷射的几何机制，该机制包含一个轴向入口和三个切向入口。引入了分割比参数，用于描述通过这些入口的气流比例。在四个不同的分割比（SR 1,2,3,4）下，流体形成直径为30mm的单一增强喷射，通过3D RANS数值模拟预测冲击传热。还对传统环形喷射和由自制几何叶片旋流器生成的喷射进行了计算，研究了雷诺数（Re = 6000至15000）和喷射-平板距离（H = 1.5D至4D）下的流动结构。通过计算比较了所有喷射的流动结构，并讨论了粒子图像测速（PIV）流动可视化结果。对所有喷射的冲击传热特性进行了数值分析。研究表明，在较小的喷射-平板距离H=1.5D时，增强喷射和叶片旋流器喷射的传热性能优于传统环形喷射。相比之下，传统环形喷射在H=4D时传热最大。通过比较研究发现，使用所提增强喷射在优化距离H=1.5D和分割比SR=4时，平均努塞尔数（Nu_avg）比传统环形喷射提高了88%，比叶片旋流器喷射提高了101%。同样，所提增强喷射在SR=4时预测的滞止努塞尔数（Nu_stg）比传统环形喷射提高了189%。
英文摘要：
A geometrical mechanism that generates augmented swirling and round jets is being proposed. The proposed geometry has an axial inlet port and three tangential inlet ports, each of diameter 10mm. A parameter called Split ratio, defined as the percentage of airflow split through these inlet ports, is introduced for the augmented jet. Flow at four different split ratios(SR 1,2,3, and 4) results in a single augmented jet of swirling and round jets of diameter D = 30mm, for which impingement heat transfer is predicted using 3D RANS numerical simulations. Also, computations for conventional round jets and swirling jets generated by an in-house geometrical vane swirler of 45, 60 and 30 degree vane angles each of jet diameter D = 30 mm are performed for the Reynolds number (Re = 6000 to 15,000) and at a jet-plate distance (H = 1.5D to 4D). A comparative study of the flow structures for all the jets using computations is done, followed by a limited discussion on Particle Image velocimetry (PIV) flow visualization results. An impingement heat transfer analysis for all the jets is studied numerically. It is inferred that at a smaller jet-plate distance H =1.5D, the augmented jet and vane swirler jets showed an improved heat transfer from the impingement surface (heated flat plate). In contrast, the conventional round jets showed maximum heat transfer at H = 4D. From the comparative study, the impingement heat transfer characteristics using the proposed augmented jet are better at an optimized jet-plate distance H=1.5D and at a split ratio (SR 4), with an enhancement in the average Nusselt number (Nu avg) of 88% than the conventional round jet and 101% than the vane-swirler jet counterpart. Similarly, an enhancement in the stagnation Nusselt number (Nu stg) of 189% than the round jet is predicted for the proposed augmented jet at SR-4.
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