When Cooling is Critical

Part 1: Cooling: Assess Overall Heat Gain to Calculate Loads

Part 2: Rent or Buy Cooling Equipment? Three Considerations

Part 3: Data Centers: Design Principles for Providing Critical Cooling

Part 4: Cooling Equipment: Technician Training

Part 5: Calculating Cooling: Load-Factor Definitions

Data Centers: Design Principles for Providing Critical Cooling

By Thomas A. Westerkamp - July 2009 - Data Centers

Early designs for data centers created a host of cooling problems due to poor layout, resulting in hot and cold air mixing. Some specific layout solutions sought to improve basic designs of data centers by using raised metal floors and drop ceilings. These improvements relied on the principle of improving efficiency through high temperature differences — delta T — between hot and cold air.

Managers have a number of proven design principles to provide the necessary cooling:

• Hot aisles between cabinets should be hot, and cold aisles should be cold.

• Use the area above the drop ceiling as a return plenum for hot air.

• Place ducts to the return plenum above hot-air aisles.

• Duct hot air directly from the return plenum to the cooling inlets to isolate it from data-center equipment.

• Place barriers above and below cabinets to prevent hot and cold air from mixing

• Locate power cables and telecommunication cables outside the airflow space so they do not obstruct airflow.

• Seal off cable penetrations carefully to prevent air infiltration.

• Place cabinet rows parallel to the airflow to reduce turbulence.

• Use a separate, central makeup air handler to regulate humidity.

The key to keeping the cooling compatible with the heat gain is to know each component of the gain as accurately as possible, as well as its incremental effect on the cooling load. Managers can determine this most effectively by accurately measuring the load — airflow through the servers, delta T between entering and exiting air, and power used when servers are idle and when loaded.