Optimizing Appliance Position and Hood Configuration

1 “Hot air rises!” This introductory sentence to Design Guide 1 states the obvious. But why does it sometimes rise and stay within the hood envelope and other times fill the kitchen with smoke, grease, and heat? Recent research sponsored by the American Society of Heating, Refrigeration, and Air-conditioning Engineers (ASHRAE) provided intriguing insights into this question. In addition to the more obvious “it depends on the amount of exhaust air” factor, this ASHRAE research demonstrated that hood style and construction features, as well as the positioning of appliances beneath the hood, had a dramatic influence on the ability of the hood to capture and contain. By making what might appear to be subtle changes to the design engineer, installing contractor or kitchen manager, a surprisingly wide range in the exhaust rates required for complete capture and containment (C&C) can occur due to appliance position and/or hood configuration. Within the real world of commercial food service, this explains why a similar hood installed over virtually the same appliance line performs successfully in one kitchen while the same design may fail in another. The key to performance is in the design details!