Indoor airflow and pollutant spread inside the cleanroom with micro-porous supplying panel and different ventilation schemes: Analytical, numerical and experimental investigations

Abstract

The airflow distribution and human thermal comfort at different supply airflow rates, as well as cleanliness recovery characteristic of indoor pollutant were numerically and theoretically investigated in a Class 10, 000 cleanroom. Computational fluid dynamics models of the cleanroom with three ventilation schemes, where the position of the micro-porous air supplying panel was altered to create unidirectional low-turbulence flow, were built and validated by the on-site measurements that carried out in a full scale test room. The results of theoretical analysis of cleanliness recovery characteristic were compared with numerical ones, to identify whether the decay equation could accurately predict the cleanliness recovery characteristic of different ventilation schemes. It was found that air distribution was generally uniform, and a small temperature gradient was still observed. Air change rate (ACH) played an important role in the indoor airflow field, and particularly it has a distinct effect on the deflection and the distribution of thermal plume (e.g. in the scheme of lateral ventilation). For large ACH, removal of pollutant (e.g. in the scheme of combined ventilation) could be enhanced, whereas there was a risk of thermal discomfort (e.g. in the scheme of vertical ventilation). Furthermore, decay equation was demonstrated that it was not suitable for all ventilation for predicting the cleanliness recovery time. Present work certainly adds to our understanding of the micro-porous panel ventilation in cleanrooms. Present investigation has a number of important implications for future cleanroom practice.