An improved wall-mounted displacement ventilation system in a large-span machining workshop.

A machining workshop requires ventilation that removes oil mist particles efficiently and conditions air to a comfortable temperature. Displacement ventilation has been reported to be highly efficient in removing airborne pollutants in a workshop. However, the traditional wall-mounted displacement ventilation system may be inadequate for delivering conditioned, clean air to the internal zone of a large-span workshop. This investigation proposed an improved wall-mounted displacement ventilation system in which machining equipment is elevated, relay fans are operated in corridors in the cooling season, and ceiling air exhausts are lowered. The proposed ventilation system was compared with the traditional wall-mounted displacement ventilation system and a displacement ventilation system with multiple local diffusers in the corridors, separately. A validated computational fluid dynamics (CFD) software program was used to investigate the three ventilation systems in both the cooling and heating seasons. The airflow, oil mist particle concentration, and air temperature under the three ventilation systems were evaluated. The results revealed that the traditional wall-mounted displacement ventilation system is inappropriate for use in a large-span workshop, particularly in the cooling season. The proposed improved wall-mounted displacement ventilation provided the lowest oil mist particle concentration in the breathing zone and an appropriate air temperature in the occupied zone in both the cooling and heating seasons. Notably in the cooling season, the proposed system reduced the oil mist particle concentration by 48.5% in the breathing zone as compared with the traditional system. Such an improved ventilation system is highly recommended for use in large-span workshops. [ABSTRACT FROM AUTHOR]