Ever wander through a supermarket and past the open refrigerated cases that house cream cheese, butter and OJ? The refrigerated shelves are protected by jets of air that blow across the front. These jets form an air shield to keep the warm air out.
Trouble is, it doesn’t always work. The cases use extra energy to cool the air that leaks in. So researchers tested the ubiquitous cases. They shot air across the front to try out a variety of speeds, angles and other factors. They used a tracer gas to measure warm air infiltration.
And they found that the key players are the angle of the air grills and what’s called a Reynolds number—which involves the air jet’s speed and density and the jet’s turbulence.
By adjusting these variables, they were able to get a ten percent reduction in warm air infiltration. Which the researchers say could save $100 million worth of electricity each year. The research was published in the journal Applied Thermal Engineering. [Mazyar Amin, Dana Dabiri and Homayun K. Navaz, "Comprehensive study on the effects of fluid dynamics of air curtain and geometry, on infiltration rate of open refrigerated cavities"]
The researchers have designed a system so that fridge case manufacturers can optimize their companies’ designs. And save us all some cold cash.
—Cynthia Graber
