Jet impingement heat transfer (JIHT) is a technique deployed in various cooling/heating applications. The heat transfer (HT) and flow structure of a confined circular air impinging jet on a flat plate with a circular row of novel droplet roughness elements are numerically investigated utilizing the RNG k-ε turbulence model. The effects of Reynolds number in the range between 7,000 and 35,000, the location of the droplet roughness elements (DREs) relative-to-jet diameter (<InlineEquation ID="IEq1"> <EquationSource Format="TEX">$s/d$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>s</mi> <mo stretchy="false">/</mo> <mi>d</mi> </mrow> </math></EquationSource> </InlineEquation>) of 1.5, 2, 2.5, and 3 and confinement plate height (<InlineEquation ID="IEq2"> <EquationSource Format="TEX">$H/d$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>H</mi> <mo stretchy="false">/</mo> <mi>d</mi> </mrow> </math></EquationSource> </InlineEquation>) of 0.25, 0.5, 1, and 1.5 are studied. The distribution of surface temperature, local Nusselt number (<InlineEquation ID="IEq3"> <EquationSource Format="TEX">$\it {\text{Nu}}$</EquationSource> <EquationSource Format="MATHML"><math> <mtext mathvariant="italic">Nu</mtext> </math></EquationSource> </InlineEquation>), average Nusselt number (<InlineEquation ID="IEq4"> <EquationSource Format="TEX">$\it {\text{Nu}}_{{{\text{avg}}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext mathvariant="italic">Nu</mtext> <mtext mathvariant="italic">avg</mtext> </msub> </math></EquationSource> </InlineEquation>), average Nusselt number ratio (<InlineEquation ID="IEq5"> <EquationSource Format="TEX">$0\it {\text{Nu}}_{{{\text{avg}}/phantom{i}{\text{.r}}}}$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0</mn> <msub> <mtext mathvariant="italic">Nu</mtext> <mrow> <mtext mathvariant="italic">avg</mtext> <mo stretchy="false">/</mo> <mi mathvariant="italic">phantom</mi> <mi mathvariant="italic">i</mi> <mtext mathvariant="italic">.r</mtext> </mrow> </msub> </mrow> </math></EquationSource> </InlineEquation>), velocity distribution, streamline contours, turbulence kinetic energy (TKE), and static pressure (<InlineEquation ID="IEq6"> <EquationSource Format="TEX">$p$</EquationSource> <EquationSource Format="MATHML"><math> <mi>p</mi> </math></EquationSource> </InlineEquation>) drop are discussed. In addition, the performance evaluation criterion (<InlineEquation ID="IEq7"> <EquationSource Format="TEX">$\it {\text{PEC}}$</EquationSource> <EquationSource Format="MATHML"><math> <mtext mathvariant="italic">PEC</mtext> </math></EquationSource> </InlineEquation>) is assessed to evaluate the overall performance of the confined jet impingement. The results show that the presence of droplet roughness elements considerably influences the rates of heat transfer. At <InlineEquation ID="IEq8"> <EquationSource Format="TEX">$s/d$</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>s</mi> <mo stretchy="false">/</mo> <mi>d</mi> </mrow> </math></EquationSource> </InlineEquation> = 1.5, H/d = 0.5, and Re = 35,000, the <InlineEquation ID="IEq9"> <EquationSource Format="TEX">$\it {\text{Nu}}_{{{\text{avg}}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext mathvariant="italic">Nu</mtext> <mtext mathvariant="italic">avg</mtext> </msub> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq10"> <EquationSource Format="TEX">$\it {\text{Nu}}_{{{\text{avg}}/phantom{i}{\text{.r}}}}$</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext mathvariant="italic">Nu</mtext> <mrow> <mtext mathvariant="italic">avg</mtext> <mo stretchy="false">/</mo> <mi mathvariant="italic">phantom</mi> <mi mathvariant="italic">i</mi> <mtext mathvariant="italic">.r</mtext> </mrow> </msub> </math></EquationSource> </InlineEquation>, and <InlineEquation ID="IEq11"> <EquationSource Format="TEX">$\it {\text{PEC}}$</EquationSource> <EquationSource Format="MATHML"><math> <mtext mathvariant="italic">PEC</mtext> </math></EquationSource> </InlineEquation> equal 127, 2.45, and 2.88, respectively. As well, DREs significantly reduce the recirculation zone downstream of the roughness elements.

Effect of droplet roughness elements on heat transfer and fluid flow over a plate subjected to a confined air jet

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2026年8月3日

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Mustafa Abdelfattah,
Ahmed Sowayan,
Mohamed A. Aziz,
Sabbah Ataya,
Hussein M. Maghrabie

摘要

Jet impingement heat transfer (JIHT) is a technique deployed in various cooling/heating applications. The heat transfer (HT) and flow structure of a confined circular air impinging jet on a flat plate with a circular row of novel droplet roughness elements are numerically investigated utilizing the RNG k-ε turbulence model. The effects of Reynolds number in the range between 7,000 and 35,000, the location of the droplet roughness elements (DREs) relative-to-jet diameter ( $s/d$ $s / d$ ) of 1.5, 2, 2.5, and 3 and confinement plate height ( $H/d$ $H / d$ ) of 0.25, 0.5, 1, and 1.5 are studied. The distribution of surface temperature, local Nusselt number ( $\it {\text{Nu}}$ $Nu$ ), average Nusselt number ( $\it {\text{Nu}}_{{{\text{avg}}}}$ ${Nu}_{avg}$ ), average Nusselt number ratio ( $0\it {\text{Nu}}_{{{\text{avg}}/phantom{i}{\text{.r}}}}$ $0 {Nu}_{avg / phantom i .r}$ ), velocity distribution, streamline contours, turbulence kinetic energy (TKE), and static pressure ( $p$ $p$ ) drop are discussed. In addition, the performance evaluation criterion ( $\it {\text{PEC}}$ $PEC$ ) is assessed to evaluate the overall performance of the confined jet impingement. The results show that the presence of droplet roughness elements considerably influences the rates of heat transfer. At $s/d$ $s / d$ = 1.5, H/d = 0.5, and Re = 35,000, the $\it {\text{Nu}}_{{{\text{avg}}}}$ ${Nu}_{avg}$ , $\it {\text{Nu}}_{{{\text{avg}}/phantom{i}{\text{.r}}}}$ ${Nu}_{avg / phantom i .r}$ _, and $\it {\text{PEC}}$ $PEC$ equal 127, 2.45, and 2.88, respectively. As well, DREs significantly reduce the recirculation zone downstream of the roughness elements.