Not everyone is keen to join the free air cooling pioneers, especially those who are in the business of meeting climate control demands for mission critical IT systems.
Peter Rolls, national manager of Power Protection, says computer rooms require precision planning and are very different to meeting the air conditioning needs of a residential environment.
“Server rooms require precision conditioning systems that ideally have a modular construction format so they can adapt economically to expansion,” he says.
Air conditioners have four basic components: a pump, an evaporator, a condenser, and an expansion valve. However, unlike cooling systems for general use, those used for IT applications are best optimised for that specific application and therefore incorporate special technology.
For example, the Citec Genesis system distributed by Power Protection utilises a scroll compressor for the refrigerant.
“The scroll compressor, unlike piston compressors, can be perfectly counter-balanced, thus minimising vibration,” Rolls says.
Because the scroll suction and discharge take place during a full rotation (compared to a ¼ rotation for piston-driven compressors), the flow of refrigerant is much smoother with lower noise levels and higher efficiency.
All systems have a working fluid and an opposing fluid as well, acting as a heat exchange medium, and power ratings vary from five kW to 110 kW.
Fans are needed to move the air, and methods include forward and backward arrangements of fan blades for centrifugal impellers.
At the heart of the control system is an electronic expansion valve (EEV) controlling the cooling action of the refrigerant. The inlet pressure passes up to the pilot solenoid.
The linear proportional solenoid is a device that modulates the amount of fluid passing through it based on its input signal. Provision is made for real-time superheat monitoring to detect the loss of refrigerant through system leaks.
The evaporation unit absorbs heat from the chilled water heat exchanger and twin loops or tandem cooling loops can be arranged. An electronically controlled electrode-boiler humidifier is provided as well as air filters protected by a differential pressure switch to indicate proper functioning of the filters. Two main ways of air conditioning are available: up-flow and down-flow.
The design of server racks is critically important although strictly speaking is not an integral part of the cooling system, Rolls says. “Yet without proper design, the cooling task is compromised.”
The use of integrated server racks are designed for use in high power density computer rooms and to eliminate hot aisles.
The cool air supply, coming in through the perforated, raised computer room floor, is directed to the top of the integrated rack by means of a dual (hot swappable/redundant) axial fan unit.
The hot air exiting from the server rack is then passed to the computer room cooling equipment.
Pressure transmitters within the rack monitor airflow and possible obstructions, while temperature sensors monitor inlet and outlet temperatures and together with the pressure transmitters, activate alarms.
The fan unit can include an LCD readout unit, or this can be separately mounted in the Citec server rack.
“This is very specialised technology and shows how server rooms requires specialised equipment as well as strategic planning to get it right,” Rolls says.