Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.
Air curtains in open refrigerated vertical display cases are designed for creating an invisible barrier between the cold air inside and the warm air outside of the case. A modular display case is built to allow the variation of flow and geometrical parameters. This unit is used 1) to directly measure the infiltration rate as a function of all of these parameters by using a tracer gas, and 2) to understand the fluid dynamics of the air curtain, by using Particle Image Velocimetry (PlY) technique. Based on this study, an artificial neural network (ANN) program was developed that assisted the researchers in specifying those flow parameters and geometrical configurations that minimized the infiltration rate, and the cooling load thereafter. A display case, based on these design specifications, was fabricated and tested. A 13 percent reduction in the infiltration rate was produced which translates into $200 M savings, and approximately 0.5 M tons of reduction in green house gases in the United States. The temperature of the food was also monitored, and in all cases met the Food and Drug Administration (FDA) requirements. The research also indicated a potential additional 13-15 percent- improvement in savings.