Optimisation of low energy cooling through phase variation between adjacent piezoelectric fan blades

Piezoelectric fans are highly efficient and low energy air-movers. The technology may be applied to reduce the power requirements of thermal management systems in a range of power electronics. The understanding of piezoelectric fan arrays, in which multiple blades are beneficially coupled, is of paramount importance for the research field. In the present research, a numerical model consisting of two piezoelectric fan blades is developed and validated against previous experimental work. The model is used to investigate the effect of phase variation, phi, between two adjacent piezoelectric fan blades in face-to-face orientation, operating within a channel. When phi not equal 0 degrees, 180 degrees, an asymmetrical flow domain is observed. Considering an incremental increase of phase variation from phi = 0 degrees, the skewness of the downstream velocity profile is increased heavily when phi <= 60 degrees, whilst the magnitude of the average downstream velocity is only enhanced when phi >= 75 degrees. The generated skew is attributed to the dominance of one vortex over another between the adjacent blade faces during their opening period. At peak skewness (phi = 75 degrees), the vortex behind the phase leading blade is 101% larger than its counterpart. Evenly matched vortices between the two blades are optimal for generating peak mass transfer. This is observed when the blades are in counter-phase, phi = 180 degrees. Conclusions in the present study build upon and are in good agreement with those previously published. (C) 2019 Elsevier Ltd. All rights reserved.