An experimental and numerical study on heat transfer enhancement of a heat sink fin by synthetic jet impingement
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ORIGINAL
An experimental and numerical study on heat transfer enhancement of a heat sink fin by synthetic jet impingement Longzhong Huang 1 & Taiho Yeom 2 & Terrence Simon 1
&
Tianhong Cui 1
Received: 6 October 2019 / Accepted: 22 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Compared to traditional continuous jets, synthetic jets (jets with oscillatory flow such that the time-average velocity is zero) have specific advantages, such as lower power requirement, simpler structure and the ability to produce an unsteady turbulent flow that is known to be effective in augmenting heat transfer. This study presents experimental and computational results that document heat transfer coefficients associated with impinging a synthetic jet flow onto the tip region of a longitudinal fin used in an electronics cooling system. The effects of different parameters, such as amplitude and frequency of diaphragm movement and jetto-cooled-surface spacing, are recorded. The computational results show a good match with experimental results. In the experiments, an actual-scale (1 mm jet orifice) system is introduced and, for finer spatial resolution and improved control over geometric and operational conditions, a large-scale mock-up (44 mm jet orifice) is applied in a dynamically-similar way, then tested. Results of the experiments at the two scales, combined with the computational results, describe fin heat transfer coefficients on and near the jet impingement stagnation point. A linear relationship for heat transfer coefficient versus frequency of diaphragm movement is shown. Heat transfer coefficient values as high as 650 W/m2K are obtained with high-frequency diaphragm movement. Cases with different orifice shapes show how jet impingement cooling performance changes with orifice shape. Keywords Synthetic jet . Forced convection . Electronics cooling . Heat transfer enhancement
Nomenclature A heat transfer area (m2). Am diaphragm amplitude (mm). d diameter of circular orifice (m). dh hydraulic diameter of orifice (m). f frequency of diaphragm movement (Hz). havg average heat transfer coefficient (W/m2K). k thermal conductivity (W/mK). L length of the fin (m). Nu average Nusselt number. q heat power input (W). R radius of the fin tip (m). Re Reynolds number. * Terrence Simon [email protected] 1
Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
2
Department of Mechanical Engineering, University of Mississippi, University, MS 38677, USA
St Strouhal number. Ts surface temperature (°C). Tair Temperature of ambient air (°C). U time-average speed of jet (m/s). Umax spatially-averaged peak jet velocity (m/s). W width of the fin (m). z distance between orifice and fin tip (m). Greek symbols μ dynamic viscosity of fluid (N∙s/m2). ν kinematic viscosity of fluid (m2/s). ρ density of fluid (kg/m3). ω angular velocity (rad/s). Subscripts avg. average. max maximum.
1 Introduction Thermal management of electronic devices has become a progressively serious issue f
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