Performance of large fan-filter units for cleanroom applications

Fan-filter units (FFUs) are widely used in clean space to re-circulate and remove particles out of the airflows directed to cleanrooms or minienvironments. Energy and aerodynamic performance of FFUs may largely influence both energy efficiency and effectiveness in contamination control in the cleanroom design, qualifications, and operation. This article presents laboratory-measured performance of seven relatively new and large FFUs, with a section size of 122-cm×122-cm, or 4-ft×4-ft. In addition, this article includes a comparison of the performance of these large FFUs with that of smaller, 122-cm×61-cm (or 4-ft×2-ft) FFUs that were previously tested. The comparison was based upon a set of performance metrics such as total pressure efficiency (TPE) and energy performance index (EPI). This article found that there were wide variations in the energy performance of FFUs, and that using a consistent evaluation method can generate comparable FFU performance information. When operating at the maximal setting of speed control dials used to control their respective fan-wheel speeds, the larger units in this study tended to be more energy efficient than their smaller counterparts. The energy efficiency level of the same unit may vary considerably, depending on actual operating conditions such as airflow speeds and pressure rise across the units. Furthermore, this article provides recommendations for further investigations to improve energy efficiency of FFU applications.