Convective heat transfer on a flat surface induced by a vertically-oriented piezoelectric fan in the presence of cross flow

Convective heat transfer on a flat surface induced by a vertically-oriented piezoelectric fan in... Experimental tests are carried out to investigate the convective heat transfer performances on a flat surface around the vibration envelope of a vertically-oriented piezoelectric fan in the presence of cross flow. Distinct behaviors of convective heat transfer are illustrated under the present conditions of piezoelectric-fan excitation voltage (U = 50, 150, 250 V) or characteristic velocity (u PF = 0.83, 1.67, 2.34 m/s) fan tip-to-heated surface gap (G = 3, 5, 7 mm) and cross flow velocity (u CH = 0.94, 1.56 m/s). In addition, three-dimensional flow field simulations are conducted to illustrate the instantaneous flow fields around the vibrating fan. By comparing with the pure piezoelectric fan, the vortex induced by the vibrating fan is pushed downward by the cross flow and a series of vortices are displayed down the vibrating fan. It is confirmed that the presence of cross flow is contributive to the improvement of convective heat transfer in the rear zone downstream fan vibration envelope. The impingement role of streaming flow induced by piezoelectric fan is reduced by the presence of cross flow in the fan vibration envelope. On the other hand, the oscillating movement of the piezoelectric fan promotes the disturbance intensity of cross flow passing through the fan vibration envelope. These two aspects make the conjugated convective heat transfer in the vicinity of fan vibration envelope complicated. In general, the convective heat transfer in the vicinity of fan vibration envelope is mostly improved by the combined action of fan-excited steaming flow and cross flow in the situation where the piezoelectric fan is placed very close to the heated surface. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Heat and Mass Transfer Springer Journals

Convective heat transfer on a flat surface induced by a vertically-oriented piezoelectric fan in the presence of cross flow

Convective heat transfer on a flat surface induced by a vertically-oriented piezoelectric fan in the presence of cross flow

Heat Mass Transfer (2017) 53:2745–2768 DOI 10.1007/s00231-017-2019-2 ORIGINAL Convective heat transfer on a flat surface induced by a vertically‑oriented piezoelectric fan in the presence of cross flow 1 1 1 Xin‑Jun Li · Jing‑zhou Zhang · Xiao‑ming Tan Received: 29 September 2016 / Accepted: 13 March 2017 / Published online: 22 March 2017 © Springer-Verlag Berlin Heidelberg 2017 Abstract Experimental tests are carried out to investigate steaming flow and cross flow in the situation where the pie - the convective heat transfer performances on a flat surface zoelectric fan is placed very close to the heated surface. around the vibration envelope of a vertically-oriented pie- zoelectric fan in the presence of cross flow. Distinct behav - List of symbols A Vibration amplitude of fan-tip (m) iors of convective heat transfer are illustrated under the present conditions of piezoelectric-fan excitation voltage A Peak to peak amplitude of fan-tip (m) pp D Hydraulic diameter (m) (U = 50, 150, 250 V) or characteristic velocity (u = 0.83, PF 1.67, 2.34 m/s) fan tip-to-heated surface gap (G = 3, 5, f Vibrating frequency (Hz) G Fan tip-to-surface distance (m) 7 mm) and cross flow velocity ( u = 0.94, 1.56 m/s). In CH addition, three-dimensional flow field simulations are con - h Convective heat transfer coefficient [W/(m K)] H Inner height of channel (m) ducted to illustrate the instantaneous flow fields around the vibrating fan. By comparing with the pure piezoelec- k Thermal conductivity [W/(m K)] L Exposed length of fan (m) tric fan, the vortex induced by the vibrating fan is pushed downward by the cross flow and a series of vortices are L PZT length (m) L Streamwise distance for average displayed down the vibrating fan. It is confirmed that the presence of cross flow is contributive to the improvement L Lateral distance for average Nu Nusselt number of convective heat transfer in the rear zone downstream fan vibration...
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Publisher
Springer Berlin Heidelberg
Copyright
Copyright © 2017 by Springer-Verlag Berlin Heidelberg
Subject
Engineering; Engineering Thermodynamics, Heat and Mass Transfer; Industrial Chemistry/Chemical Engineering; Thermodynamics
ISSN
0947-7411
eISSN
1432-1181
D.O.I.
10.1007/s00231-017-2019-2
Publisher site
See Article on Publisher Site

Abstract

Experimental tests are carried out to investigate the convective heat transfer performances on a flat surface around the vibration envelope of a vertically-oriented piezoelectric fan in the presence of cross flow. Distinct behaviors of convective heat transfer are illustrated under the present conditions of piezoelectric-fan excitation voltage (U = 50, 150, 250 V) or characteristic velocity (u PF = 0.83, 1.67, 2.34 m/s) fan tip-to-heated surface gap (G = 3, 5, 7 mm) and cross flow velocity (u CH = 0.94, 1.56 m/s). In addition, three-dimensional flow field simulations are conducted to illustrate the instantaneous flow fields around the vibrating fan. By comparing with the pure piezoelectric fan, the vortex induced by the vibrating fan is pushed downward by the cross flow and a series of vortices are displayed down the vibrating fan. It is confirmed that the presence of cross flow is contributive to the improvement of convective heat transfer in the rear zone downstream fan vibration envelope. The impingement role of streaming flow induced by piezoelectric fan is reduced by the presence of cross flow in the fan vibration envelope. On the other hand, the oscillating movement of the piezoelectric fan promotes the disturbance intensity of cross flow passing through the fan vibration envelope. These two aspects make the conjugated convective heat transfer in the vicinity of fan vibration envelope complicated. In general, the convective heat transfer in the vicinity of fan vibration envelope is mostly improved by the combined action of fan-excited steaming flow and cross flow in the situation where the piezoelectric fan is placed very close to the heated surface.

Journal

Heat and Mass TransferSpringer Journals

Published: Mar 22, 2017

References

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