Analysis and Experiments on the Characteristics of Airflow and the Air Cleanliness Protection Region under Fan Filter Units in Cleanrooms

Abstract

Cleanrooms often utilize large amounts of supply air to achieve a required cleanliness level. To reduce the overall supply air volume, critical processes demanding the highest cleanliness requirements are suggested to be placed directly beneath the air outlet of fan filter units (FFUs). In order to determine an appropriate supply air volume, it is necessary to quantitatively analyze the particulate concentration distribution downstream of FFUs with various characteristics to determine an adequate but not excessive supply air volume. Three FFU sizes and four supply air velocities were used in this experiment, and the resulting airstream velocities, jet diffusion widths, and characteristics of particulate concentration distribution were obtained. Fitting expressions were statistically acquired based on the respective experimental data sets, which can be used to predict the airflow velocity value at any point in an FFU flow region and the width of the air cleanliness protection range.