MEASURED AND PREDICTED FLOWS IN FUME CUPBOARDS

Measurements of tracer gas concentration and velocity profiles have be en made around several different designs of sash handle on a modern ae rodynamic fume cupboard. These have shown that large regions of high g as concentrations can occur under the handles, even those of an aerody namic design, and extend towards their outer edges. Laser Doppler anem ometer measurements have shown that these regions correspond to ones w here the now moves outwards from the cupboard with very low airspeeds. Handle design strongly influences the size of these regions. Computat ional fluid dynamics (CFD) predictions of the velocity flow fields aro und two of the handles, using FLOW 3 D (a suite of programmes for the prediction of laminar and turbulent flows) with a low Reynolds number k-epsilon turbulence model, shows excellent agreement with measured va lues. Calculated and measured concentration profiles also show good ag reement. For further comparison, the position of the flow separation c lose to the back baffle was measured; good agreement with the CFD pred iction is found.