An experimental study on the influences of air change rate and free area ratio of raised-floor on cleanroom particle concentrations

Control of indoor contaminants is a common practice in cleanroom facilities using ventilation systems with higher airflow rate. However, it is arbitrarily postulated that the ventilation systems are often over designed and are inevitably energy intensive. Several cleanroom required airflow rate model based on simplified theoretical basis have been proposed [9-14], but have not been thoroughly verified. This study presents an experimental investigation on the effect of room air change rate (hereafter referred as ACH) and free area ratio of raised-floor (hereafter referred as beta) on particle concentration, conducted in a full-scale, non-unidirectional, raised-floor cleanroom equipped with a mini-environment facility. Four different ACHs (60, 81, 103 and 146 h(-1)) were evaluated with four varied beta (24%, 30%, 36% and 48%) and challenge particles at 100,000 counts/ft(3) (for particles with 0.1 mu m in diameter). Experimental results demonstrate that the increase of ACH and beta resulted in the decrease of particle concentration. Besides, the influence of beta on particle concentration is more significant at low ACM cases compared to those at high ACH cases. The experimental data in this study can be a validation base for the previous proposed cleanroom required airflow rate models. (C) 2011 Elsevier Ltd. All rights reserved.