基于合成双射流的Al_(2)O_(3)纳米流体散热数值研究

Numerical investigation on heat dissipation of Al_(2)O_(3) nanofluid based on dual synthetic jets

使用Al2O3纳米流体对基于合成双射流激励器的通道强化换热进行了数值研究,分析了不同体积分数的纳米流体对通道冷却性能的影响。激励器工作后,膜片往复振动,在射流口产生了交替吸入与喷出的射流并冲击基板,装置的冷却性能大大提高。同时,纳米颗粒的加入增大了流体的导热系数,流体传热性能有所提高,但同时也增加了进出口压降。引入了综合性能评价因子KFOM和整体传热增强度KDTE,发现随着纳米流体体积分数的增加,KFOM和KDTE也增大,这表明使用纳米流体后,整体装置的冷却性能有一定程度的提升。此外,分析了激励器频率和等效振幅对散热的影响,结果表明:频率对装置整体散热性能影响较小;随着等效振幅增大,射流速度增大,芯片温度降低,装置整体冷却性能更好;激励器工作后也同样影响纳米颗粒在通道内的分布情况,每一时刻下纳米颗粒的分布都不尽相同,且聚集在基板底部的纳米颗粒将会增强换热效果,这也是影响整个装置散热性能的重要因素。

In the present paper,the enhancement of heat transfer based on dual synthetic jets actuator(DSJA)in a channel with Al2O3 nanofluid is numerically studied,and the effects of nanofluid volume fraction on the cooling performance is analyzed.The reciprocating vibration of the actuator’s diaphragm produces alternately inhaled and ejected jets impacting the substrate at the jet port,improving the cooling performance of the device significantly.Meanwhile,nanoparticles increase the thermal conductivity of the fluid,thereby improving the heat transfer performance,but the pressure drops at the inlet and outlet are increased.It is found that the figure of merit(FOM)and degree of thermal enhancement(DTE)values increase with the nanofluid volume fraction,indicating the improvement of the cooling performance to a certain extent by using nanofluids.Moreover,this paper also analyzes the influence of the frequency and equivalent amplitude of the actuator on heat dissipation.The results show that the frequency barely affects the overall heat dissipation performance of the device.By comparison,as the equivalent amplitude increases,the magnitude of the jet velocity increases,the chip temperature decreases,and the cooling performance of the device is better.The working actuator also affects the distribution of nanoparticles in the channel,manifested by the temporally varying distributions of nanoparticles.Those nanoparticles gathered at the substrate bottom will enhance the heat transfer,an essential factor affecting the heat dissipation of the device.