數值預測濕式清洗檯上混合對流安全評估

Numerical Simulation on the Mixed Convection about Wet Bench for Safety Assessment

濕式清洗檯（Wet Bench）是清洗過程主要作業環境之一。不同的污染物（例如微 粒、氧化物及金屬不純物）在濕式清洗檯內利用不同化學藥品清洗，在此過程中，由化學藥品蒸發的氣體對工作人員可能具有潛在的危險。為了評估濕式清洗檯的安全問題，本研究利用二維空間數值預測模擬在濕式清洗檯上流場及有害氣體的行為。由於影響因素太多，本文只探討影響流場及有害氣體的擴散運動相關的四種因素（吸氣速度，吹氣速度，下降速度及史密特數）。根據本文的計算模擬結果發現清洗過程如使用同向吹吸式氣罩則對工作人員有潛在危險，相反地，如使用逆向吹吸式氣罩或在槽縫罩上方加裝檔板則任何吸氣速度及史密特數情況下，危險氣體都可以得以良好控制。此外，本文研究結果可以協助改善濕式清洗檯的設計，利用適當的局部排氣系統在清洗過程時排除有害氣體。

Wet bench is a typical working apparatus for cleaning process. A variety of contaminations such as particle, oxide and metal impurity are cleaned in a wet bench by using different solution. During the cleaning process, the vaporizing gas from solution is hazardous to workers. In order to assess the safety of wet benches, two-dimensional numerical simulation was conducted to understand the behavior of air flow and hazardous gas. This study only investigated four factors (push velocity, pull velocity, downward velocity and Schmidt number) that effect flow motion and hazardous gas distribution. The study also disclosed that danger for cleaning process might occur in the case of adopting horizontal push-pull hood. On the other hand, when a vertical push-pull hood or an additional baffle is used, the hazardous gas could be controlled well at any exhausted velocity and Schmidt number. Moreover, for setting up a safe wet bench, the finding of this study could help us to design local ventilation systems to exhaust hazardous gas during the cleaning process.