Investigation of a Dual-sided Multiple Fans System with a Piezoelectric Actuator
Date Issued
2015
Date
2015
Author(s)
Li, Yi-Tseng
Abstract
This thesis developed a cooling device of the dual-sided multiple fans system with a piezoelectric actuator (D-MFPA), which is able to drive eight passive vibrating fans and provide two-directional air flows by using only one piezoelectric actuator. The geometric effects of the D-MFPA and two types of the fan designs, viz. magnetic fan (MF) and composite magnetic fan (CMF) were also explored. In the investigation of the MF, the results indicated that the resonance frequency of the D-MFPA increased from 27.6 Hz to 66 Hz as the length of the carbon fiber plate (L) decreased from 55 mm to 35 mm. It also decreased the amplitude of the D-MFPA from 12.4mm to 4.8 mm. For CMF, the results showed that the resonance frequency decreased when the length of the Mylar plate (E_l) increased, and the maximum decrease was from 66 Hz to 45 Hz when L= 35 mm and E_l= 30 mm. M_MFPA and M_(D-MFPA) were defined to describe and quantify the improvement in the thermal performance as the one-sided and dual-sided multiple fans were applied for cooling, respectively. The results showed that the optimal M_(D-MFPA) of single piezoelectric fan was 1.58 for cooling one heat source. By contrast, under the same power consumption, the D-MFPA not only cooled two heat sources but also displayed better thermal performance; moreover, the CMF design in the D-MFPA system should be applied in the D-MFPA and the range of E_l/L was controlled at 0.22-0.50 to attain better thermal performance. In the investigation of the D-MFPA in LEDs thermal management, the several horizontal orientations (〖x/S〗_l) and vertical orientations (〖y/S〗_h) were examined to investigate the effects of different arrangements and further improve the thermal performance of the D-MFPA. The results indicated that M_(D-MFPA) can be improved to 3.92 under the case of 〖x/S〗_l= 0 and 〖y/S〗_h= 0.033; however, the single piezoelectric fan can only improve M_(D-MFPA) to 2.82. To improve the thermal performance of the multiple fans system by different way, this thesis also investigated the effect of the housing design on the MFPA. The results indicated that the geometry of the housing can significantly influence the thermal performance of the modular MFPA. The airflow generated from the MFPA was concentrated when Z^* decreased from 2.5 to 1.25 at Y^*=0.917 and θ= 0°; the results showed T^* (t) decreased from 0.76 to 0.67. Moreover, under the case of Z^*= 1.25 and θ= 0°, T^* (t) further decreased from 0.67 to 0.60 when Y^* decreased from 0.917 to 0.417. To optimize the thermal performance of the modular MFPA, a nozzle was applied for concentrating airflow. The results showed an optimal value of M_MFPA of 2.57 when the nozzle angle (θ) was 63.43° under the case of Z^*= 1.25, Y^*= 0.417.
Subjects
D-MFPA
composite magnetic fan
LEDs
thermal performance
optimization
dimensionless analysis
module design
nozzle angle
Type
thesis
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