[Airflow equation of a slot hood by the least square method].

Objectives: In designing a local exhaust ventilation (LEV) system, the exhaust airflow rate which will produce the required control velocity at the capture point must be predicted properly. Conventionally, the airflow requirements for LEV hoods have been calculated using Dalla Valle's equation. Although Dalla Valle's equation is a simple and convenient formula for LEV design, it is known that the airflow rate predicted by the equation does not always coincide with actual exhaust airflow rate. In order to develop a new airflow formula which can substitute for Dalla Valle's equation, the author aimed to develop an empirical airflow formula for a slot type exhaust hood using the least square method.

Methods: Based on the actual measurements (exhaust airflow rate, suction velocity, hood size and centerline distance) of test slot type hoods in several configurations and conditions, an empirical approximation formula which predicts exhaust airflow rate was developed. In this study, the approximation formula was described as a polynomial linear expression, and the validity of the predicted exhaust airflow rate by the approximation formula was confirmed by comparing with measured airflow rates.

Results: It was found that the predicted airflow rates of the developed approximation formula were in good agreement with the measured airflow rates and were more accurate than the airflow rates predicted by Dalla Valle's equation.

Conclusions: Although the applicability of the developed formula is inferior to that of Dalla Valle's equation, certain economic benefits can be derived from the developed formula in some cases.