Direct Free Cooling
This is when outdoor air is pushed into the IT container to directly cool hardware. For this to happen outdoor conditions need to be suitable and the system must be supported by either a chilled water or DX system for when outdoor conditions are not suitable.
How does it work?
The DFC modules consist of fans and modulated dampers which control which air enters the IT area, either the outdoor air, indoor air or a blend of both.
Each module is composed by 3 sets of dampers in order to open/close the airflow to the IT container. The monitoring system regulates closing-opening of the dampers.
- Supply air damper (x%)
- Exhaust air damper (x%)
- By-pass damper (100-x%)
It is also necessary to provide filtering to the incoming air to prevent dust and other air pollutants from entering the data centre, this is done in accordance with EN 779.
Dependent on outdoor conditions 3 modes of operation are possible:
Mode 1: 100% DFC
Dampers d1 and d2 are 100% open, and d3 is closed. All supplied air is from outside towards IT container. Warm air is expelled towards outside with intake air pressure given by the fan.
Fan modulates airflow needed to cool the IT area. Outdoor T> Return air limit of freecooling arrives when external temperature achieves the maximum temperature that can accept the cool corridor under design conditions
Mode 2: <100% >0% DFC
System modulates Dampers (d1, d2, d3) mixing the fresh air with the recycled air to achieve the correct supply conditions.
Outdoor air is filtered before entering cooling container. Filtering efficiency depends on the site and quality required.
Warm air is expelled towards outside with the intake air pressure given by the fan. The fan modulates the airflow needed to cool the IT area.
Mode 3: 0% DFC
Dampers d1 and d2 are 100% closed, and d3 is 100% open. All the supply air is recycled.
Support cooling system is on, cooling the return air to the design conditions by the coil (c1)
Two cooling systems available: Chilled water (CW) or Direct Expansion (DX). Fan modulates the airflow needed to cool the IT area.
Direct Free Cooling in a brick and mortar data centre
DFC modules can be sited inside the data centre and outdoor air is ducted to them for when suitable outdoor conditions exist.