An investigation into flow and heat transfer of an ultrasonic micro-blower device for electronics cooling applications

Abstract

Due to copyright restrictions, the access to the full text of this article is only available via subscription.As compact electronics increase in functionality, new electronics cooling approaches must be more effective, and they must be lower in form factor. In this paper, we investigated the cooling performance of a miniature ultrasonic micro-blower impinging upon a vertical heater. We studied the temperature response at different operating conditions, determining the optimal thermal conditions. We further examined the local flow field using the particle image velocimetry (PIV) technique at the same operating conditions, providing explanations for the heat transfer response in terms of the fluid dynamics. Heat transfer measurements show that the maximum cooling performance occurs at a jet-to-surface spacing ratio of 15 < H/D < 30, and the performance slowly decays when the jet is located further away. The preferred operating frequency of the piezoelectric cooling device occurs at an ultrasonic frequency of over 20 kHz, meaning that this device can function outside the human hearing range. The PIV results demonstrate that the jet profile in the near field deviates significantly from a traditional turbulent free jet. In the far field, it nearly matches the self-similar, fully-developed jet profile. The jet cooling performance is sensitive to the frequency, with the thermal performance dropping by a factor of six when varying by less than 1 kHz from the peak. At the optimal heat transfer condition, the coefficient of performance is measured at approximately three, which is lower than that of some synthetic jets.TÜBİTA

Analytical and experimental study of a valveless piezoelectric micropump with high flowrate and pressure load

“…The flexure connection structures between the central plate and the fixed surrounding part determine the working frequency of the actuator. The width and thickness of the flexure connection structures are optimized to obtain a working frequency just above 22 kHz, which is higher than the maximum sound frequency that humans can hear 22 . However, the working frequency should not be too high, as the loss from vibrations increases with increasing vibration frequency.…”

Schlieren Flow Visualization and Analysis of Synthetic Jets

“…Year Frequency Jet Type Study Type (Hz) Kercher et al [6] 2003 1-1000 synthetic Travnicek and Tesar [8] 2003 106-692 synthetic smoke Smith and Swift [1] 2003 synthetic and Schlieren continuous Pavlova et al [9] 2006 420-1200 synthetic Arik [10] 2008 4500 synthetic Chaudhari et al [11] 2009 100-350 synthetic Bazdidi-Tehrani et al [12] 2011 16-400 synthetic Biden et al [13] 2012 unforced jet POD in crossflow Biden et al [14] 2012 forced jet POD in crossflow Ghaffari et al [15] 2016 20,000 ultrasonic microblower Ghadi et al [16] 2016 pulsed smoke impinging jet Albright and Solovitz [17] 2016 variable-diameter synthetic jet Firdaus et al [18] 2018 300-700 synthetic Solovitz et al [19] 2018 350-2000 synthetic PIV Viggiano et al [20] 2018 variable-density POD and PIV jet Kristo et al [21] 2021 crossflow jets POD and PIV Present work 2021 20-100 synthetic POD, smoke, Schlieren Pavlova et al [9] found that high-frequency jets removed heat more effectively, but that lower-frequency jets were better for larger separation distances. Many authors found that the optimal frequency for heat transfer was the resonance frequency for the device or the diaphragm [11,18,19].…”

“…Many authors found that the optimal frequency for heat transfer was the resonance frequency for the device or the diaphragm [11,18,19]. Recent work has pushed devices to frequencies with lower acoustic impact [15] and explored the option of variable diameters [17]. In all these applications, there is a need for the optimization of the synthetic jet using low-cost visualization methods that can be applied in industry.…”

Flow topology and heat transfer analysis of slotted and axisymmetric synthetic impinging jets

“…Experimental and numerical studies have been devoted to analyze the di↵erences on flow topology between the slotted and axisymmetric configurations. The former has been the subject of many scientific numerical and experimental studies (see for instance [18][19][20]), while the latter seems to be preferred in industrial applications [21][22][23][24]. In spite of this, to the authors' knowledge few numerical works have been focused on the comparison of both synthetic jets.…”