Numerical investigation into the influence of air curtain discharge angles in refrigerated trucks

Abstract

Over the years, the use of air curtains has been considered as one of the most effective ways of preventing warm-air infiltration in cold storages and now in refrigerated trucks as well. It is estimated that energy savings of almost 40% can be achieved using an air curtain. Previous studies have suggested that the energy efficiency of air curtains could be further improved through several mechanical adjustments, including the adjustment of discharge angle. This study focuses on the influence of different discharge angles on air curtain mechanisms and energy performance for an air curtain with warm-air suction (ambient air intake). The results suggest that adjusting the angle in the positive direction (outwards) can help prevent the bending in the discharge jet- created as a result of dominating natural convection showing a discharge angle of 10° to be more effective in controlling the bend than 0°. However, the effectiveness of the discharge angle is highly dependent on the discharge velocity. When the discharge velocity is low (2 m/s), the released jet is too weak and hence the effect of the discharge angle is also small, resulting in similar recovery energy for both the 0° and 10° cases. However, when the discharge velocity is medium to high (above 4 m/s in this case), the bending effect is also significant and hence adjusting the discharge angle can prove to be more advantageous, providing an energy saving of up to 17.6%.