Data Clean Asia

The Hot-Aisle /Cold-Aisle Design

The hot-aisle /cold-aisle design is a long-standing data center best practice. It requires lining up server racks in alternating rows with cold-air intakes all facing one aisle and hot-air exhausts facing the other. This configuration optimizes cooling effectiveness and efficiency by ensuring that only cold supply air is delivered to the equipment inlets. Cold aisles must be populated with airflow floor panels or grilles (raised floor distribution) or ceiling grilles (overhead distribution). The 7-foot server cabinets create a tunnel effect so that the heated air in the hot isle can be directed to the CRAC unit. Over the past several years, it became the de facto standard. But as server densities have increased, efficiency gains have consequently eroded.

In a typical data center that is configured using hot aisles and cold aisles, the cold air from the cold aisles wraps around the ends of the aisles and mixes with the hot air before it has a chance to get to the CRAC. This lowers the exhaust air temperature before it returns to the CRAC inlet. Lower CRAC return temperatures cause the CRACs to short cycle which causes additional inefficiencies and higher energy costs to operate.

Mixing of warm return air with cold supply air will cause the temperature in the cold aisle to rise. Traditionally, the most common way to prevent these hot-spots was to increasing the number of cooling units. While this may appear to solve the problem, the added cooling capacity does not offer precision cooling, which will help curb costs and improve energy efficiency.

With so much effort underway to improve the efficiency of data centers; cold and hot aisle containment are one of the proven ways to eliminate hot-spots, reduce cold-air loss, and cut energy dollars.

Aisle Curtain

Aisle containment system in the last couple of years has become the next logical step from hot and cold aisles due to the improvement of data center cooling efficiency. Aisle containment system enhances the hot aisle/cold aisle design by retaining the cold air in the cold aisle. By closing off the ends of the cold aisles, it stops the cold air from escaping. The blocking of obvious cold-air escape provides more consistent inlet temperatures to the servers while helping the CRAC units to operate more efficiently with higher inlet temperatures (thereby saving energy). The isolation also eliminates hot spots. This increases reliability while still achieving ideal cooling conditions.

According to Bruce Myatt of EYP Mission Critical, the separation of hot and cool air “is one of the most promising energy-efficiency measures available to new and legacy data centers today.” (Mission Critical Magazine, Fall 2007). A study by Lawrence Berkeley National Laboratory (LBNL) demonstrated that facilities that install partitions to more precisely direct the airflow can save energy on both air conditioning and fan systems - 15% and 67%, respectively.

Aisle containment system has been in place for many multinational companies as environmental pressures and energy costs increase. Storage vendor NetApp uses curtains in their data center and says that curtains alone save them 1 million kWh of energy per year. One of the USA Yahoo data centers uses them as well.

Bank in Singapore installed air curtains

Before
·          Cold aisles were very close to CRAC units
·          Excessive short-cycling
·          19° CRAC inlet temperature

After
·          25° CRAC inlet temperature
·          Eliminated CRAC short-cycling
·          Increased CRAC set-points to 23°
·          Improved efficiency

Aisle Curtain system offered by Data Clean Asia that could help you improve your data center's efficiency and save you money on your energy bills:
(click on the link to view its contents)

1) AirStop Aisle Curtain Partial Containment
2) Trax Aisle Curtain Full Containment