Investigation of fan law accuracy for small scale electronic cooling blowers

摘要

The trend for notebook computers is towards thinner and lighter systems. These systems requirethinner and more effective cooling solutions including thinner blowers. In this paper, theaccuracy of the fan scaling laws was numerically investigated as blower size is reduced to verythin form factors. Fan laws were originally derived for relatively large fans and blowers, withmuch higher Reynolds numbers than seen in these very small and thin blowers. The validity offan laws in devices at these small scales is currently uncertain. Numerical simulations wereperformed for three blowers with the dimensions of 20×20×3 mm, 40×40×6 mm, and60×60×9 mm, where the first two numbers represent the footprint of the blower and the third isthe height along the axis of rotation. Blower simulation results for the largest configuration(60×60×9 mm), which is typical for current notebook designs, are compared to experimentaldata, and good agreement between the model and the measurements is observed. Theexperimental results for this largest case are scaled down using the fan laws and compared to thenumerical results for the smaller geometries. Good agreement between the simulation and thescaled experimental results are observed, and the fan laws are determined to be accurate for theselow Reynolds number small scale blowers. The acoustic fan scaling laws are used to compareairflow performance for the different blower sizes at the same acoustic noise condition. Inaddition to the fan scaling study, an investigation was conducted on the acoustic impact of mounting a notebook scale blower on an acoustic plenum, and a significant acousticamplification was observed in the lower frequency range.