阀体孔板
材料科学
机械
传热
停滞点
合成射流
努塞尔数
粒子图像测速
孔板
湍流
热力学
光学
物理
雷诺数
机械工程
电气工程
工程类
执行机构
作者
Lei Wang,Li-Hao Feng,Yi Xu,Yang Xu,Jin-Jun Wang
标识
DOI:10.1016/j.ijheatmasstransfer.2022.122760
摘要
• Unsteady temperature information of noncircular impinging synthetic jets is first obtained by thermographic phosphor thermometry. • Square orifice displays better stagnation cooling performance through deeper penetration of the wall shear layer. • Secondary structures lead to AR = 5 rectangular orifice producing a double-peak heat transfer feature in the major-axis direction. • First reported double-peak distribution of wall temperature for rectangular impinging synthetic jets. • AR = 5 rectangular orifice achieves optimal cooling performance with the maximum time-averaged cooling area. This study investigates the flow characteristics and unsteady heat transfer of noncircular synthetic jets impinging on a heated plate. Thermographic phosphor thermometry and time-resolved particle image velocimetry are used to acquire quantitative wall temperature and flow field information, respectively. At a constant orifice-to-wall distance ( H / D e = 7.5), five orifice configurations (circular, square, elliptic with aspect ratio (AR) of 3, and rectangular with ARs of 3 and 5) are examined at a wall temperature of 80 °C. The orifice configuration has a significant effect on the heat transfer and vortex behavior of the impinging synthetic jets. The square orifice displays better stagnation cooling performance with 42% increase in the maximum stagnation cooling coefficient relative to the circular case due to the larger impinging velocity and deeper penetration into the wall shear layer. Axis-switching of the vortex rings is detected for both the elliptic and rectangular orifices before they impinge onto the wall. The axis-switching enhances the near-wall mixing and turbulent kinetic energy in the elliptic and rectangular orifices, and thus heat transfer compared with the circular case. Additionally, stronger vortices and deeper penetration into the wall shear layer are observed in the major-axis plane than in the minor-axis plane, leading to enhanced heat transfer in the major-axis direction. In particular, the rectangular orifice with an AR of 5 induces strong secondary structures in the trailing jet following the primary vortex ring, and these are responsible for the double-peak distribution of wall temperature in the major-axis direction. This is the first time a double-peak temperature distribution has been reported for noncircular impinging synthetic jets. The rectangular orifice with an AR of 5 also yields a larger cross-stream velocity in the minor-axis direction, indicating a stronger wall jet. Thus, among the cases considered in this study, the rectangular orifice with AR = 5 achieves the optimal cooling performance and the maximum time-averaged cooling area reaches more than 14 times the jet orifice area.
科研通智能强力驱动
Strongly Powered by AbleSci AI