Infrared Imaging Results of an Excited Planar Jet

Planar jets are used for many applications including heating, cooling, and ventilation. Generally, a planar jet provides good mixing within an enclosure. In building applications, the jet provides both thermal comfort and adequate indoor air quality. Increased mixing rates may reduce short circuiting of conditioned air, eliminate dead zones within the occupied zone, reduce energy costs, increase occupant comfort, and increase indoor air quality. This article discusses how an infrared imaging system was used to demonstrate how jet excitation affected the spread angle and the jet mixing efficiency. Infrared imaging captures a large number of data points in real time (over 50,000 data points per image) providing significant advantages over single-point measurements. We used a mesh screen with a time constant of approximately 0.3 seconds as a target for the infrared camera to detect temperature variations in the jet. The infrared images show that excitation of the jet caused increased jet spread. Digital data reduction and analysis show changes in jet isotherms and quantify the increased mixing caused by excitation.