How CoolSim models a CRAC in a raised-floor room: the four thermal boundary conditions, fan curves, resizing, and saving units to a library.
This video explains how to model a computer room air conditioner (CRAC) in a raised-floor data hall in CoolSim. It covers building a unit from the default object and using the library.
What the video shows
- Dragging in the default cooling unit, which knows it sits in a raised-floor room with a ceiling plenum return. The outlet and return are drawn as colored outlines, and the arrows show air direction.
- The editor: changing the unit type from downflow to front flow (in-row) or upflow, entering a manufacturer and model number, and changing color and size.
- Entering the flow rate of the unit being modeled, and a cooling capacity, which appears in the output report. A unit that exceeds its capacity shows in red there.
- The four thermal boundary conditions:
- Supply temperature, the default, holds a constant supply air temperature. It treats the unit as able to deliver unlimited cooling.
- Cooling capacity uses a thermostat on the return (the default) or the supply, and adjusts the supply until the average return matches the setpoint. It takes longer to solve and assumes a linear link between return temperature and capacity.
- Temperature drop.
- Performance data, a table of up to 10 entries relating return temperature to capacity.
- On, off and fan-only states. Arrows on the unit disappear when it is off.
- Fan curves as an alternative to a constant flow rate, entered as a table from the manufacturer.
- Resizing a unit: the supply and return do not scale with the geometry, so the modify supply and modify return dialogs and the auto distribute button resize them to match.
- Naming a unit and adding it to the user library from the right-click menu, using the library for pre-set units, and exporting a unit as a small CSO file.
Tips
- The presenter prefers the supply temperature condition. A measured supply temperature, for example taken at a lifted tile with an infrared thermometer, makes it a good setting for design optimization.
- Performance data is not always easy to get. The presenter says what is available is already in the library units, and it covers some manufacturers far better than others.
- Fan curves are rarely needed, and the presenter says they matter mostly when a fan cannot overcome the pressure needed under the floor.