| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 102 === An inclined air-curtain (IAC) fume hood was characterized by using the laser-assisted smoke flow visualization technique and tracer-gas (sulphur hexafluoride) concentration detection method. Four innovatory designs were included in the IAC fume hood. Baffles used in the conventional hoods were not required. The suction slot and the up-blowing planar jet formed a rearward-inclined push-pull air curtain. The deflection plates worked with the inclined air curtain to induce four rearward-inclined counter-rotating “tornados.” The fumes generated in the hood were isolated behind the reward-inclined air curtain, entrained by the low-pressure within the vortical flows, went up spirally, and finally exhausted through the suction slot. The risk of containment leakage induced by the large recirculation vortex usually existed behind the sash of conventional hoods was reduced by the boundary-layer separation controller. The results of tracer-gas concentration detections based on the EN-14175 method showed that the flow field created by the geometric configurations of the IAC hood presented characteristics of low leakage and high potential of resisting dynamic disturbances at low face velocities. The leakage levels of the static, sash movement, and walk-by tests were negligibly small at the face velocity of 0.26 m/s. The results of tests based on the ANSI/ASHRAE method also showed negligibly small leakages (less than 0.004 ppm) even at a large sampling probe velocity of 2 m/s
|
|---|
