How to model overhead downflow cooling units, often called rooftop units, in a non-raised floor room with a ceiling plenum, and read the results.
This video models downflow cooling units mounted in the ceiling, sometimes called rooftop units, that blow air straight down into a cold aisle.
What the video shows
- Set up a non-raised floor room with a 10 foot ceiling plenum. A cooling unit dragged in defaults to an in-row type, so right-click it and change the type to downflow.
- Set the unit geometry (3 by 4 feet, 3 feet high in the demo) and start it at the room height so it sits overhead.
- Set the airflow and supply temperature in the thermal tab, then copy and paste the unit. The demo uses 10,000 cubic feet per minute (CFM) at 60 degrees Fahrenheit.
- Add end-cap baffles that leak slightly to contain the cold aisle, and ceiling grills to let the air return.
- In the results, path lines show cold air filling the aisle, and return air leaving through the grills with little coming over the racks.
- The summary report shows airflow supplied and demanded nearly matched, with Return Temperature Index (RTI) and Rack Cooling Index (RCI) high at 100 percent. RCI low was slightly low because the air was cold, so the presenter notes the supply temperature could be raised to save energy.