Effects of the stroke length and nozzle-to-plate distance on synthetic jet impingement heat transfer

Abstract

This study focuses on the combined effect of the nozzle-to-plate distance and of the stroke length on the cooling performances of impinging synthetic jets.Infrared thermography is used as temperature transducer in conjunction with the heated thin foil heat transfer sensor to measure time-and phase-averaged convective heat transfer. All the experiments have been performed at a fixed Reynolds number equal to 5,250, while different values of the dimensionless

Application of Optical Flow Analysis to Shadowgraph Images of Impinging Jet

“…Hence, shadowgraph images were used for analysis. Figure 6(a) shows that, in the shear layer of the free jet, a vortex due to the KH instability [16] is generated of the shear layer at around x/D = 2.0. This vortex develops into a coherent structure as it approaches the wall (Figure 6(b) and Figure 6(c)), and then its traveling direction is changed along the wall in the impinging jet region (Figure 6(d)).…”

“…In general, the flow field is roughly divided into three areas: i) a free jet region [13], ii) an impingement or stagnation region [14], and iii) a wall jet region [15]. In the free jet region, primary vortices with counterclockwise rotation are formed by the Kelvin-Helmholtz [KH] instability [16] of the shear layer and advect along the shear layer. In the wall jet region, secondary vortices with clockwise rotation are formed near the wall.…”

Evaluation of anisotropic tangential conduction in printed-circuit-board heated-thin-foil heat flux sensors

“…This latter term is typically negligible although, when performing experiments with relatively low values of the Nusselt number, it can have a significant impact, e.g. up to 17% of ′′ [17]. Within this context, a recent work by Sarkar et al [18] reports that non-uniformities of the convective heat transfer coefficient (and thus temperature) require local corrections.…”

Cooling performance improvement of impingement hybrid synthetic jets in a confined space with the aid of a fluid diode

“…Ingenious cooling schemes are absolutely essential to achieving effective thermal management of electronic devices to keep their temperatures within a suitable range. A promising cooling technology, called an impingement synthetic air jet, has gradually attracted widespread attention [4][5][6][7], due to its obvious advantages as follows compared with conventional cooling methods, such as natural convection, fan, steady jet: (1) a synthetic jet exhibits higher heat transfer capacity, which can be 4.5-10 times [8], 1.2-1.4 times [9] and 1.4 times [10] higher than those of natural convection, fan and steady jet, respectively; (2) it has no rotating parts, which are conducive to noise reduction, low energy consumption, stability, safety and reliability; (3) it does not need fluid pipe and complex pumping, offering a compact structure and ease of integration. Based on the above advantages, an impingement synthetic air jet is considered to be a more efficient manner for cooling of electronic devices, especially in limited space.…”