The Challenge

Late in the 1990′s cutting edge heavy users of technology began to express concerns with traditional cooling methods for rack mounted data processing equipment. Problems at first were anecdotal; failure rates for servers located near the top of the rack seemed greater. While still limited to relatively high end users, the problems with high density data processing equipment heat loads are now well documented. There has also been recognition that the computer cabinet can be an integral part of the solution to cooling the equipment.

As legacy equipment is replaced by the latest generation technology with the associated higher watt densities, more and more users are experiencing unacceptable temperature gradients within cabinets. In many cases the existing computer room air conditioning systems capacity is sufficient to cool the high density equipment but air flow issues prevent consistent cooling particularly higher in the rack. A method to provide adequate cooling to this density equipment is needed. The solution requires all the following attributes.

1 – Effectively Provide Constant Temperature Air Throughout the Rack, Bottom to Top

The air needs to be delivered to the air inlets of the equipment where it can be used to maximize heat transfer from the internal components. Any cooling air not dawn internally through the equipment will not effectively cool. The air temperature is ideally a few degrees above the new dew point, providing the lowest processor operating temperature without condensation. Cooling needs to be controlled and directed. Where there are blank spaces in racks or non heat generating equipment (i.e. patch panels) there is no need for cooling air. Further, certain equipment air inlets can be at the front while others have side air intakes.

2 – Work Within Existing Data Center Constraints So As Not To Cause Disruption To Existing IT Equipment

Manufacturers introduce new generations of technology equipment at rapid rates, with product cycles of 18 months to 2 years. Users however deploy this new technology at a slower rate. Constrained by budget limitations the new technology is used to replace obsolete systems in a more gradual methodology with a first in first out approach. Business use of existing equipment can not be interrupted while mew infrastructure is installed. Infrastructure improvements can be expensive and have long leave times. Often by the time they can funded, designed and constructed the data processing equipment they were intended to support has become obsolete. The risk to ongoing operations when installing new systems, equipment and interconnections is significant often with high financial impact for interruptions of business functions.

3 – Maximize Use Of Existing Air Conditioning Infrastructure

Often data centers develop unacceptable temperatures in high density areas even though air conditioning systems are not at capacity. Several factors can contribute to this, however, there can be many problems with existing raised floor plenum air distribution systems including bypass airflow, obstructed air flow, low static pressure and mixing of computer exhaust with with inlet air. Computer Room Air Conditioner(CRAC) units operate most efficiently with higher return air temperatures. Air bypassing the equipment inlets will return to the CRAC units at cooler temperatures effectively lowering the design capacity of these units. When cooling air is provided directly to the inlets of the data processing equipment, maximum heat transfer will occur and the CRAC units will operate at maximum efficiency and up to their full rated capacity.

4 – Eliminate Air Flow Restrictions Within the Cabinet

Unobstructed air flow to the inlets, through the equipment and return to the CRAC units is essential. Air brought into cabinets through cut outs in the floor is blocked by the lowest server in the cabinet and not only does not provide effective cooling but also reduces static pressure under the floor further reducing air flow through perforated tiles (increasing temperature gradients). Cabling systems must also be managed to allow free flow of exhausted hot air away from the equipment.

5 – Be of High Quality but Affordable and Simple To Implement For All Levels of Users of IT Equipment

Cabinets need to be flexible enough to be used with a wide range of equipment from different manufacturers. New cabinets for high density equipment need to be rolled into an existing facility and populated with equipment and perform the business function intended without expensive infrastructure improvements and associated delays.

6 – Cool Up to 10KW Per Cabinet with 70 Degree F Inlet Air and 30 Degree F Temperature Rise Through the Equipment

There is upper limit restriction where infrastructure needs limit the actually deployable density that can be reached in a data center This however does not limit the amount of power (therefore heat dissipated) consumed by individual cabinets. A cabinet with up to 10KW of load is high but not unseen in the industry. Properly utilized air conditioning systems can provide 70 degree air without risk of condensation in most applications. 70 degree air directed to computer equipment inlets will transfer enough heat to cause a 30 degree rise in the discharge air.