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On heat transfer and flow characteristics of jets impinging onto a concave surface with varying jet arrangements

  • Dandan Qiu
  • Chenglong WangEmail author
  • Lei Luo
  • Songtao Wang
  • Zhiqi Zhao
  • Zhongqi Wang
Article
  • 28 Downloads

Abstract

The increase in hot gas temperature is helpful for the turbine efficiency improvement and energy-saving. The significantly curved leading edge suffers the highest thermal load in a turbine blade. Jet impingement is one of the popular heat transfer enhancement methods, which has been widely used in blade leading edge. In this study, the flow structure and heat transfer characteristics of jets impinging onto a curved surface with varying jet arrangements and Reynolds number (10,000–40,000) are numerically investigated. The relative jet-to-target spacing equals 1, and relative surface curvature equals 10. An array jets arrangement is provided as baseline. Concerning three array cases, jet holes are positioned in inline and staggered patterns with changing jet-to-jet spacing. In this work, streamlines of different sections, limiting streamlines near target wall and vortex, are obtained. Local Nusselt number contour, local Nusselt number curves and surface-averaged Nusselt number are also presented. Local heat transfer characteristics are analyzed with fluid flow. It is also shown that the heat transfer uniformity of both inline and staggered cases is significantly enhanced by comparing with an array jets case. The whole curved surface-averaged Nusselt number increases with increasing jet-to-jet streamwise spacing at inline arrangement.

Keywords

Heat transfer Fluid flow Jet impingement Concave 

List of symbols

\(d_{\text{jet}}\)

Jet diameter, \({\text{mm}}\)

\(D\)

Target wall diameter, \({\text{mm}}\)

\(D_{1}\)

Upper surface diameter, \({\text{mm}}\)

\(f\)

Friction factor

\(f_{\text{s}}\)

Friction factor for an array jet

\(h\)

Heat transfer coefficient, \({\text{W}}\, {{\text{m}}^{-2} \;{\text{K}^{-1}}}\)

\(l\)

Flow length, \({\text{mm}}\)

\(L\)

Jet-to-jet spacing between middle and adjacent side jets at Y direction, \({\text{mm}}\)

\({\text{Nu}}\)

Nusselt number

\({\text{Nu}}_{\text{ave}}\)

Averaged Nusselt number

\({\text{Nu}}_{{{\text{ave}},{\text{s}}}}\)

Averaged Nusselt number for an array jet

P

Jet-to-jet spacing for the same line jets at Y direction, \({\text{mm}}\)

\(P_{i}\)

Inlet mass flow average total pressure, \({\text{Pa}}\)

\(P_{\text{o}}\)

Outlet mass flow average total pressure, \({\text{Pa}}\)

\(q\)

Heat flux, \({\text{W}} {\text{m}}^{-2}\)

\({\text{Re}}\)

Jet Reynolds number

\(S\)

Streamwise direction along the concave target surface

\(T_{\text{i}}\)

Jet inlet temperature, \({\text{K}}\)

\(T_{\text{w}}\)

Impingement wall temperature, \({\text{K}}\)

\(U_{\text{i}}\)

Jet inlet velocity, \({\text{m}}\, {\text{s}^{-1}}\)

\(Z\)

Jet-to-impingement surface spacing, \({\text{mm}}\)

\(\theta\)

Degree between the middle array jets and side arrays, \(^\circ\)

\(\lambda\)

Fluid thermal conductivity, \({\text{W}}\, {{\text{m}^{-1}}\;{\text{K}^{-1}}}\)

\(\mu\)

Fluid dynamic viscosity, \({\text{Pa}}\;{\text{s}}\)

\(\rho\)

Fluid density, kg m−3

Notes

Acknowledgements

The author acknowledges the financial support provided by the Natural Science Foundation of China (No. 51706051), China Postdoctoral Science Foundation funded Project (No. 2017M620116), Heilongjiang Postdoctoral Fund (No. LBH-Z17066) and the Fundamental Research Funds for the Central Universities (Grant No. HIT.NSRIF.2019061).

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Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2019

Authors and Affiliations

  • Dandan Qiu
    • 1
  • Chenglong Wang
    • 2
    Email author
  • Lei Luo
    • 1
  • Songtao Wang
    • 1
  • Zhiqi Zhao
    • 1
  • Zhongqi Wang
    • 1
  1. 1.School of Energy Science and EngineeringHarbin Institute of TechnologyHarbinChina
  2. 2.Science and Technology on Scramjet LaboratoryNational University of Defense TechnologyChangshaChina

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