Effectiveness and optimum jet velocity for a plane jet air curtain used to restrict cold room infiltration

The effectiveness of a 1.0 m wide air curtain fitted over a 1.36 m wide entrance to a cold store has been evaluated. It was shown that careful setting up of the air curtain (adjusting the jet velocity and angle) was needed, this achieved an effectiveness of 0.77 compared to the initial value of only 0.31 as set by the installer. An analytical model to predict the optimum jet velocity was compared to measured data. It is important to choose the correct safety factor (an increase in the jet velocity) for this model, as an effectiveness of between 0.37 and 0.70 could be produced using the range of safety factors found in the literature. A 2D computational fluid dynamics (CFD) model predicted a maximum effectiveness of 0.84 and showed how the effectiveness of the curtain was related to the shape of the jet and how this varied with jet velocity and door open duration.