Abstract
A clean room with locally air-balanced supply-exhaust ventilation system installed at ceiling is studied by means of numerical simulation based on the k-ε two-equation turbulence model. The influences of the flow obstacle upon the flow and diffusion field and so on are precisely examined quantitatively. Results are as follows. 1) The ventilation efficiency in this clean room is well expressed by the SVE (Scale for Ventilation Efficiency) 1〜3 proposed by authors. 2) An arrangement of a flow obstacle below a supply jet have a rather great influence upon the flow and diffusion field of this type clean room. However the obstacle arranged between two supply jets have less influence than that below the supply openings. 3) The slight imbalance (less than 10%) of air volume rate in local supply-exhaust system has little influence on the ventilation efficiency. 4) The large imbalance (50%) of air volume rate in local supply-exhaust system reduces the ventilation efficiency of contaminant. It is confirmed that the locally closed circuit ventilation system (Locally Air-balanced Supply-exhaust Ventilation System) arranging supply and exhaust openings at ceiling is useful method for contamination control in conventional flow type clean room.
