Effects of Different Orifice Structure on Heat Transfer Characteristics of Steel Strip Surface in an Air Impinging Freezer

Abstract

Abstract. In this paper, the fluid field in an air impinging freezing experimental table was studied by computational fluid dynamics (CFD) numerical simulation technology. The influence of the different diameter D and orifice spacing distance S on the heat transfer characteristics on the steel strip surface were analyzed, and the difference of the heat transfer effect between the orifice and slit nozzle were compared. The results show that when the orifice diameter is less, the heat transfer coefficient on the steel strip surface is less due to the effect of cross-flow. With the orifice diameter is increased, the effect of the resistance along the upstream is increased. The average Nusselt number on the steel strip surface is the highest at D=10mm. When the spacing distance is less, the distance between the first row of orifice nozzle in the upstream and the adhering wall is less and the velocity of flow is less. With the increased of spacing distance, the distance between the first row of orifice nozzle in the upstream and the last in the downstream is increased, and the effect of cross-flow is increased. The average Nusselt number on the steel strip surface is the highest at S=34mm.The effect of cross-flow under the slit nozzles is weak and the food can be better protected. The average Nusselt number on the steel strip surface under the orifice nozzles is 9.7% higher than that of the slit nozzle.