The long-term objective of this proposal is to improve the design procedure for local exhaust ventilation systems that are augmented by push or jet flows. Local exhaust ventilation remains one of the most important engineering controls used to reduce worker exposure to toxic airborne pollutants. When jets of air are combined effectively with exhaust hoods, contaminant control can be achieved over greater distances and more economically than if the hoods were used alone. Present design procedures do not permit estimates of the concentration of contaminant in the workplace or in the worker's breathing zone. This grant proposes a fundamental step in addressing this deficiency through consideration of the basic laws of fluid mechanics governing hood-jet flow fields.
The specific aims are: 1) to develop a computer code to solve the equations governing the combined flow field of a hood, jet, and cross draft; 2) to validate the computer predictions of velocity, hood capture efficiency, and contaminant distribution; and 3) to computationally simulate and experimentally validate the capture efficiency and contaminant distribution of a push-pull system for an open surface tank. Push-pull systems are frequently used to control worker exposure to carcinogens such as formaldehyde, and hexavalent chromium in the electroplating and semi-conductor industries.
