Feasibility study of CFD prediction for evaluation of commercial kitchen environments

A measurement technique was developed on capture efficiency of commercial kitchen ventilation systems affected by disturbance due to HVAC diffusers and movement of kitchen workers. In the process of development, computer simulation using RANS CFD model was applied to evaluate diffusion of gaseous contaminants emitted from commercial kitchen appliances and compared with experiments. CFD results suggested that supply air flow from the displacement ventilation system to make up additional ceiling exhaust exerted little influence on capture efficiency to remove contaminated air which overflowed from the exhaust hood. It also suggested that, when overflowed contaminated air possibly elevated the surrounding concentration, that concentration level could be estimated by extrapolating secondary decay of exhaust air concentration immediately after primary decay when terminating the tracer gas dose. This measurement technique was applied to evaluate appropriate ceiling exhaust flow rate. It was confirmed that the ceiling diffuser of a HVAC system exerted little influence on capture efficiency if air velocity at the bottom front part of the capture hood was restricted to 0.4m/s. The simulated movement of kitchen workers tended to disturb buoyant plumes over the kitchen appliances and markedly lowered the capture efficiency of the hood. Capture efficiency of combustion waste gas was generally higher in low radiation cooking appliance with concentrated exhaust flue than that of the conventional type.