Modeling and measurement of dynamic air exchange of a machining cabin with the surroundings after opening of the cabin door

Abstract

The oil mist particles generated inside a machining cabin can leak from the cabin into the workshop and cause air pollution, once the cabin door is opened for taking out the manufactured products. However, the buoyancy-driven air exchange and the air exchange volume (AEV) across the cabin door vary with time. The dynamic AEV can be obtained by both measurement and computational fluid dynamics (CFD) modeling, but these methods are very time-consuming. This investigation proposed a simplified model to solve for the dynamic AEVs by dividing the cabin into two zones with the neutral plane as the separating interface. The dynamic temperatures of the air inside the cabin were solved on the basis of energy balance. The dynamic AEV was cast as a function of the dynamic air temperature difference between the inside and outside of the cabin. For comparison, CFD was also used to solve the dynamic AEV. Both solution methods were validated with measured data obtained in an experimental machining setup in a laboratory. The results revealed that the dynamic AEV predicted by the proposed model was in reasonable agreement with the experimental measurement. As compared with the CFD method, the simplified model had a much shorter computational time, without significantly compromising the accuracy. However, the simplified model under-predicted the time to reach thermal equilibrium in the machining cabin.