Established in 2001, ACRL faculty members and graduate students have been involved in several projects to improve the efficiency of the Open Refrigerated Display Cases (ORDCs). These systems are used almost in all supermarkets in the United States and all around the world. Previous studies have shown that up to 50% of the total energy consumption in the supermarkets can be attributed to ORDCs. The refrigeration system of an ORDC is responsible to compensate the cooling loads that are imposed to the system by different sources such as infiltration or penetration of room air that has relatively higher content of energy, lighting heat of the system, radiation from the room and heat conduction through the walls of display cases. Further investigations have indicated that among the above sources, the infiltration contribution is up to 75% of the total cooling load, which is very significant. Air curtains are currently used and have been very effective in reducing the infiltration of the display cases. Due to their higher momentum, air curtains help reduce the penetration of the room air into the ORDC.
(a) Vertical (b) horizontal ORDC (Courtesy of Hill Phoenix Co.)
Side view of a vertical ORDC with air curtain.
The overall goal of our research is to further enhance the efficiency of the display cases by improving the performance of air curtains. The studies are being conducted both experimentally and computationally. Three techniques comprise the backbone of our lab's research:
- Digital Particle Image Velocimetry (DPIV): Is used to investigate the flow structure and its variables such as mean velocity vectors, fluctuating velocities, shear stresses, air curtain spreading, impingement, etc.
- Tracer Gas Technique: This technique has been introduced and is being used for the first time to simulate and measure the infiltration of room air into the display case, without the need to the collected condensate.
- Computational Fluid Dynamic (CFD): Fluent and Gambit softwares are utilized to simulate and study both the structure of the air curtain as well as the infiltration rate.
The size of the lab is about: 16mx12mx3.5m