Deepak Jagannatha

Analysis of a Synthetic Jet-Based Electronic Cooling Module

This article presents a numerical study of an electronic cooling module using a periodic jet flow at an orifice with net zero mass flux, known as a synthetic jet. The two-dimensional time-dependant numerical simulation models the unsteady synthetic jet behavior, the flow within the cavity and the diaphragm movement while accounting for fluid turbulence using the shear-stress-transport (SST) k-ω turbulence model. Computations are performed for a selected range of parameters and the boundary conditions to obtain the heat and fluid flow characteristics of the entire synthetic jet module. The numerical simulation aptly predicts the sequential formation of the synthetic jet and its intrinsic vortex shedding process while accurately illustrating the flow within the cavity. It is indicated that the thermal performance of the synthetic jet is highly dependant on the oscillating diaphragm amplitude and frequency. At the heated surface, this jet impingement mechanism produces a very intense localized periodic cooling effect that reaches a peak with a time lag relative to the top displacement position of the diaphragm. The overall heat transfer rate of the synthetic jet module is about 30% better than an equivalent continuous jet. When compared to pure natural convection the enhancement varies from 20 to 120 times in the range of parameters studied. The study clearly identifies the outstanding thermal potential of the synthetic jet module for intense electronic cooling applications and its ability to operate without additional fluid circuits.

Performance analysis of a synthetic jet-microchannel hybrid heat sink for electronic cooling

This paper proposes a novel concept for enhancing the heat removal potential in a microchannel-based heat sinks and presents a study of its thermal performance. This technique utilises a jet mechanism that injects into the heat sinks flow passage a strong periodic fluid jet without any net mass outflow through the discharge orifice, hence termed “synthetic jet”. The flow within this microchannel-synthetic jet hybrid heat sink is modelled as a 2-dimensional finite volume simulation with unsteady Reynolds-averaged Navier-Stokes equations while using the Shear-Stress-Transport (SST) k-ω turbulence model to account for fluid turbulence. For a range of conditions, the characteristics of this periodically interrupted micro fluid flow are identified while evaluating its convective heat transfer rates. The results indicate that this pulsed jet micro-heat sink can deliver heat removal rates 4.3 times higher than an equivalent heat sink without jet mechanism. The thermal enhancement is first seen to grow gently and then rather rapidly beyond a certain flow condition to reach a steady value. The proposed strategy has the unique intrinsic ability to deliver unprecedented thermal performance in micro-heat sinks without additional fluid circuits or pressure drop. The technique has application potential in miniature electronic devices where intense localised cooling is desired over a base heat load.

Thermal performance evaluation of a synthetic jet heat sink for electronic cooling

This paper presents a performance investigation on a highly effective heat removal technique for heat sinks in electronic cooling applications. This arrangement utilises a pulsating fluid jet mechanism known as synthetic jet, which is characterised by zero net fluid discharge through the jet orifice. The study uses an experimental rig comprising a high-frequency pulsating air jet that impinges on a heated surface to emulate the heat sink operation attached to an electronic device. The cooling characteristics of this jet are examined for a range of parametric conditions, including jet-impinging distance while evaluating the heat removal rates. The results indicate that the pulsating jet produces outstanding cooling performance at the heated surface with significant dependency of it on the jet-impinging distance. The study also assesses the interaction of a cross-flow fluid stream on the pulsed jet operation. It is observed that the cross-flow somewhat impedes the pulsed jet thermal performance. However, the pulsed jet, with or without cross flow, delivers an overall cooling ability that supersedes the standard flow-through heat sink performance. This technique provides highly enhanced surface cooling potential without incurring increased fluid pressure drop or requiring additional fluid circuit, which are significant advantages for high-powered heat sink design.

Synthetic Jet-Based Hybrid Heat Sink for Electronic Cooling

Modern lifestyle is increasingly dependant on a myriad of microelectronic devices such as televisions, computers, mobile phones and navigation systems. When operating, these devices produce significant levels of internal heat that needs to be readily dissipated to the ambient to prevent excessive temperatures and resulting thermal failure. With inadequate cooling, internal heat builds up within electronic packages to raise microchip temperatures above permitted thermal thresholds causing irreparable damage to semiconductor material. Devices would then develop unreliable operation or undergo complete thermal breakdown from overheating with reduced working life. In electronic industry, 55 percent of failures are attributed to overheating of internal components. Therefore, effective dissipation of internally generated heat has always been a major technical consideration for microelectronic circuitry design in preventing overheating and subsequent device failure. In recent years, the modern microelectronic industry has shown a dramatic growth in microprocessor operating power, circuit component density and functional complexity across the whole spectrum of electronic devices from small handheld units to powerful microprocessors, as evidenced by Figs. 1 and 2.