UNSTEADY HEAT TRANSFER ENHANCEMENT IN A 3-D RECTANGULAR DUCT USING SYNTHETIC JET ACTUATOR

2015 ◽  
Author(s):  
Mohammad Moshfeghi ◽  
Byung Ha Kang ◽  
Jaisuk Yoo ◽  
Nahmkeon Hur
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Synthetic Jet ◽  
Rectangular Duct ◽  
Transfer Enhancement ◽  
Unsteady Heat Transfer ◽  
Synthetic Jet Actuator

Experimental Heat Transfer Enhancement in Single-Phase Liquid Microchannel Cooling With Cross-Flow Synthetic Jet

2010 ◽  
Author(s):  
Ruixian Fang ◽  
Wei Jiang ◽  
Jamil Khan ◽  
Roger Dougal
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Performance ◽  
Synthetic Jet ◽  
Driving Voltage ◽  
Transfer Performance ◽  
Microchannel Flow ◽  
Transfer Enhancement ◽  
Synthetic Jet Actuator ◽  
Phase Liquid

The present study experimentally investigated a new hybrid cooling scheme by combination of a microchannel heat sink with a micro-synthetic jet actuator. The heat sink consisted of a single rectangular microchannel measured 550 μm wide, 500 μm deep and 26 mm long. The synthetic jet actuator with a 100 μm diameter orifice was placed right above the microchannel and 5 mm downstream from the channel inlet. Micro jet is synthesized from the fluid flowing through the microchannel. Periodic disturbance is generated when the synthetic jet interacts with the microchannel flow. Heat transfer performance is enhanced as local turbulence is generated and propagated downstream the microchannel. The scale and frequency of the disturbance can be controlled by changing the driving voltage and frequency of the piezoelectric driven synthetic jet actuator. The effects of synthetic jet on microchannel heat transfer performance were studied based on the microchannel flow Reynolds number, the jet operating voltage and frequency, respectively. It shows that the synthetic jet has a greater heat transfer enhancement for microchannel flow at lower Reynolds number. It also shows that the thermal effects of the synthetic jet are functions of the jet driving voltage and frequency. We obtained around 42% heat transfer enhancement for some test cases, whereas the pressure drop across the microchannel increases very slightly. The paper concludes that the synthetic jet can effectively enhance single-phase liquid microchannel heat transfer performance and would have more promising enhancements if multi-jets are applied along the microchannel.

Effects of Operating Frequency of a Synthetic Jet and Cross Flow Velocity on the Heat Transfer Enhancement in a Micro-Channel

2013 ◽  
Author(s):  
Mark E. Zschirnt ◽  
Ann Lee ◽  
Guan H. Yeoh
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Cross Flow ◽  
Synthetic Jet ◽  
Operating Frequency ◽  
Micro Channel ◽  
Transfer Enhancement ◽  
Synthetic Jet Actuator ◽  
Micro Channels

Current devices have been reported to approach 1 MW/m2 so that current heat dissipation devices will not be able to cope with increasing heat flux. It has therefore been proposed that in order to manage the ever-increasing heat rejection demands, it will be necessary to have cooling fluid flowing through micro-channels in the microchip itself. Since laminar flow is likely to result for reasonable pressure drops in these micro-channels, the heat transfer rate will need to be enhanced if this approach is to be successfully used. Synthetic jets, which are the main focus of this research, generate vortex structures which disrupt the flow. They have, therefore, been proposed as a means of providing mixing, thereby augmenting the heat transfer potential of the fluid in the micro-channel. A two-dimensional computational model has been developed to investigate the cooling effect of a synthetic jet interacting with a turbulent cross-flow in a micro-channel. Validation of the hydrodynamics feature of the flow was done by comparing numerical results against existing experimental results. A parametric study was performed on a fixed geometry by using a constant wall temperature to investigate the effect of operating frequency of the synthetic jet actuator coupling with different flow rates in the micro-channel. The operating frequencies of the jet were simulated at 1000 Hz, 1500 Hz and 2000 Hz while the cross flows vary from 0 to 10 m/s. In general, the flow structures in the micro-channel were shown to be greatly disrupted when the synthetic jet actuator was turned on. However, the heat transfer enhancement due to the operation of the synthetic jet reduces as the cross flow increases. The frequency of the diaphragm oscillation has a large influence on the distance between the adjacent vortices and therefore on the average flow rate in the micro-channel. The near wall Nusselt Number was calculated in order to compare the effects of operating frequency of the jet and flow rate in the micro-channel. The jet Reynolds number was increased by 50% when the actuator frequency was increased from 1000 Hz to 1500 Hz while the heat transfer enhancement was increased by 21%. Further increment of actuator frequency from 1000 Hz to 2000 Hz resulted in a doubled jet Reynolds number while the heat transfer enhancement was improved by 66%. The heat transfer enhancement showed greater improvement when the actuator operating at 2000 Hz.

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