AEROFOIL LOUVER AIR-GRILL IN REFRIGERATED DISPLAY CABINET FOR ENERGY EFFICENCY

摘要

Air curtain is widely used in refrigerated display cabinets to reduce the air and moisture exchange between the cabinet and the surrounding ambient. Either horizontal or vertical, all air curtains need an efficient means of delivering the air jet through a kind of air-grill or honeycomb design. Honeycomb design comes with different cellular structures and jet angles to ideally create a properly profiled near-laminar air curtain fit to such applications. However, flow separation, vortex (turbulence) and significant pressure drop occurs past the commonly used “honeycomb type” air-grill due to sharp turns and inherent large wetted area inside. Some simple straight plate louver is not as effective as honeycomb in air turbulence control. An aerofoil profiled louver air-grill is developed to overcome the shortcomings of a honeycomb and a straight louver air-grill, while maintaining the good performance by the way of reducing leading and trailing edge turbulence. This design also offered efficient air turning where air jet angle needs variation for different cabinet geometry. The present study presents both a computational fluid dynamics (CFD) analysis of the proposed aerofoil design air discharge system performance, together with physical laboratory test result in refrigerated Deli-cabinet. It was found that, compared to the honeycomb air-grill, with an aerofoil based air-grill the cabinet was able to deliver AS1731 acceptable Class 3M1 product temperature with +/-0.5℃ accuracy consuming 15.1% less total energy. The refrigeration cooling capacity requirement for the test cabinet also reduced indicating a reduction of plant size by 22% is possible.