Effect of the Nozzle Geometry on Flow Field and Heat Transfer in Annular Jet Impingement

Ying Zhong, Chao Zhou and Yipeng Shi
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Ying Zhong: College of Engineering, Peking University, Beijing 100871, China
Chao Zhou: College of Engineering, Peking University, Beijing 100871, China
Yipeng Shi: College of Engineering, Peking University, Beijing 100871, China

Energies, 2022, vol. 15, issue 12, 1-22

Abstract: The effects of nozzle shape modifications on the flow phenomena and heat transfer characteristics in annular jet impingement are investigated numerically. The numerical simulations are conducted applying the shear stress transport (SST) k − ω model in the ANSYS CFX. Two modified nozzles: the converging nozzle and the diverging nozzle, are investigated in this study, and the straight nozzle serves as the base case. The geometric parameters and settings are based on an annular jet ejected from an axial fan used for electronic cooling: the Reynolds number R e = 20,000 and the blockage ratio B r = 0.35 in the computation, and the target plate is placed at three representative separation distances: H = 0.5 , 2 , and 4. Compared with the base nozzle, the converging nozzle can accelerate the cooling flow and promote turbulence to enhance local and overall heat transfer (about 20 % ) over the target surface. In addition, the converging nozzle reduces the sizes of the recirculation zones, and this promotes the convective heat transfer transport near the axis. The diverging nozzle experiences a similar flow pattern and thermal field as the base nozzle, while the diverging nozzle achieves a slightly lower heat transfer with a pronounced pressure drop reduction. In addition, given that the value of the Nusselt number over the target plate is dependent on the Reynolds number, the simulations are also performed at R e = 5000 and 40,000 to establish the correlations between the Nusselt number and the Reynolds number as N u ∝ R e m . The value of m varies depending on the nozzle shapes and the separation distances.

Keywords: jet impingement; annular jet; nozzle shape modification; heat transfer enhancement; pressure loss (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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