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<p>Optimizing convective heat transfer in compact thermal management systems require improved understanding of how vortex dynamics, confinement, and near-wall transport interact in air-based internal forced convection. This study develops a non-intrusive experimental framework that combines two-color laser-induced phosphorescence (2cLIP) with particle image velocimetry (PIV) to obtain simultaneous, high-resolution velocity and temperature fields in a confined square-duct flow with a thermally active bottom wall. Experiments were performed with and without cylindrical and square vortex generators to investigate vortex-induced mixing and heat transfer mechanisms. The coupled diagnostics enable direct evaluation of correlations between velocity and temperature fluctuations through second-order statistics. For the cylindrical vortex generator, the average heat transfer enhancement over the flat plate was approximately 25% and 13% at a Reynolds number of <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\text {Re}_{D_\text {h}}=883\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mtext>Re</mtext> <msub> <mi>D</mi> <mtext>h</mtext> </msub> </msub> <mo>=</mo> <mn>883</mn> </mrow> </math></EquationSource> </InlineEquation> and 1100, for input power to the bottom wall at <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(P_\text {plate}=6.67\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>P</mi> <mtext>plate</mtext> </msub> <mo>=</mo> <mn>6.67</mn> </mrow> </math></EquationSource> </InlineEquation> W. Increased streamwise and wall-normal velocity fluctuations intensified wake mixing, while the wall-normal turbulent heat-flux component, <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\overline{v'T'}\)</EquationSource> <EquationSource Format="MATHML"><math> <mover> <mrow> <msup> <mi>v</mi> <mo>′</mo> </msup> <msup> <mi>T</mi> <mo>′</mo> </msup> </mrow> <mo>¯</mo> </mover> </math></EquationSource> </InlineEquation> revealed a coherent and growing region of enhanced convective transport within <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(0.5 \le (x/H_\text {duct}) \le 1.8\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0.5</mn> <mo>≤</mo> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">/</mo> <msub> <mi>H</mi> <mtext>duct</mtext> </msub> <mo stretchy="false">)</mo> <mo>≤</mo> <mn>1.8</mn> </mrow> </math></EquationSource> </InlineEquation>. This structure was more spatially concentrated in the near wake of the vortex generator with greater influence into the duct core for the cylindrical geometry, and more diffusely distributed downstream for the square geometry, with limited influence into the duct core.</p>

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Simultaneous investigation of flow and thermal fields during vortex-induced heat transfer enhancement from a thermally active bottom wall of a square duct

  • 期刊论文

  • 发表日期：

    2026年7月14日

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  • Aakhash Sundaresan,
  • Atul Srivastava,
  • Callum Atkinson

摘要

Optimizing convective heat transfer in compact thermal management systems require improved understanding of how vortex dynamics, confinement, and near-wall transport interact in air-based internal forced convection. This study develops a non-intrusive experimental framework that combines two-color laser-induced phosphorescence (2cLIP) with particle image velocimetry (PIV) to obtain simultaneous, high-resolution velocity and temperature fields in a confined square-duct flow with a thermally active bottom wall. Experiments were performed with and without cylindrical and square vortex generators to investigate vortex-induced mixing and heat transfer mechanisms. The coupled diagnostics enable direct evaluation of correlations between velocity and temperature fluctuations through second-order statistics. For the cylindrical vortex generator, the average heat transfer enhancement over the flat plate was approximately 25% and 13% at a Reynolds number of \(\text {Re}_{D_\text {h}}=883\) Re D h = 883 and 1100, for input power to the bottom wall at \(P_\text {plate}=6.67\) P plate = 6.67 W. Increased streamwise and wall-normal velocity fluctuations intensified wake mixing, while the wall-normal turbulent heat-flux component, \(\overline{v'T'}\) v ′ T ′ ¯ revealed a coherent and growing region of enhanced convective transport within \(0.5 \le (x/H_\text {duct}) \le 1.8\) 0.5 ≤ ( x / H duct ) ≤ 1.8 . This structure was more spatially concentrated in the near wake of the vortex generator with greater influence into the duct core for the cylindrical geometry, and more diffusely distributed downstream for the square geometry, with limited influence into the duct core.