Communications and information technology equipment is commonly designed for mounting to racks and for housing within enclosures. Equipment racks and enclosures are used to contain and to arrange communications and information technology equipment, such as servers, CPUs, internetworking equipment and storage devices, in small wiring closets as well as equipment rooms and large data centers. An equipment rack can be an open configuration and can be housed within a rack enclosure. A standard rack typically includes front-mounting rails to which multiple units of equipment, such as servers and CPUs, are mounted and stacked vertically, and typically has a footprint of about 23 by 42 inches. The equipment capacity of a standard rack relates to the height of the mounting rails. The height is set at a standard increment of 1.75 inches, which is expressed as “U” units or the “U” height capacity of a rack. A typical U height or value of a rack is 42 U. A standard rack at any given time can be sparsely or densely populated with a variety of different components as well as with components from different manufacturers.
Most rack-mounted communications and information technology equipment consumes electrical power and generates heat. Heat produced by rack-mounted equipment can have adverse effects on the performance, reliability and useful life of the equipment components. In particular, rack-mounted equipment housed within an enclosure is particularly vulnerable to heat build-up and hot spots produced within the confines of the enclosure during operation. The amount of heat generated by a rack is dependent on the amount of electrical power drawn by equipment in the rack during operation. Heat output of a rack can vary from a few watts per U unit of rack capacity to over 1 kW per U unit, depending on the number and the type of components mounted to the rack. Users of communications and information technology equipment add, remove, and rearrange rack-mounted components as their needs change and new needs develop. The amount of heat a given rack or enclosure can generate, therefore, can vary considerably from a few tens of watts up to about 10 kW.
Rack-mounted equipment typically cools itself by drawing air along a front side or air inlet side of a rack or enclosure, drawing air through its components, and subsequently exhausting air from a rear or vent side of the rack or enclosure. Air flow requirements to provide sufficient air for cooling, thus, can vary considerably as a result of the number and the type of rack-mounted components and the configurations of racks and enclosures. Generally, most configurations and designs of information technology equipment require cooling air to flow at a rate of about 180 cubic feet per minute (cfm) per kilowatt of power consumed such that a rack drawing 10 kW of electrical power would require an air flow rate of about 1,800 cfm.
Equipment rooms and data centers are typically equipped with an air conditioning or cooling system that supplies and circulates cool air to rack-mounted equipment and enclosures. Many air conditioning or cooling systems, such as the system disclosed in U.S. Patent Application Publication No. U.S. 2001/0029163 A1, application Ser. No. 09/784,238, require that an equipment room or data center have a raised floor construction to facilitate the system's air conditioning and circulation functions. Referring to FIG. 1, the cooling system of the referenced application provides cool air by means of closed-loop air circulation and includes a raised floor 2 disposed above a base floor 5 of an equipment room. The raised floor 2 and the base floor 5 define an air passageway 6 into which an air cooling unit 14 delivers cool air. The air passageway 6 is connected to one portion of an equipment rack or enclosure 8 and is configured to channel cool air through the passageway to front portions of equipment 7 housed in the enclosure 8. Cool air flows across the equipment 7 into a plenum 8c and ascends through the plenum 8c into a plurality of ducts 24. Exhaust air vents from the ducts 24 into a return plenum 4. The return plenum 4 is connected to the air cooling unit 14 and is configured to deliver exhaust air to the air cooling unit 14 for cooling and subsequent recirculation to the equipment room.
Alternatively, air cooling systems and methods use open floor tiles and floor grills or vents to deliver cool air from the air passageway disposed below the raised floor of an equipment room. Open floor tiles and floor grills or vents are typically located in front of equipment racks and enclosures, and along aisles between rows of racks and enclosures arranged side-by-side.
The cooling systems and methods that require a raised floor construction typically do not efficiently meet the cooling requirements of rack-mounted equipment. In particular, racks that include high power equipment having a thermal exhaust air output above 5 kW and up to 10 kW present a particular challenge for such systems and methods. A raised floor construction typically provides an open floor tile or a floor grill or vent having a venting area of about 12 by 12 inches and is configured to deliver from about 200 to about 500 cfm of cool air. The air flow rate from the venting area is dependent on such factors as static air pressure and the presence of other floor tiles such that, in practice, a floor tile typically delivers from about 100 to about 200 cfm of air. A rack of high power equipment drawing up to 10 kW and requiring an air flow of approximately 1,800 cfm, therefore, would need at least about 3.5 to about 5 open floor tiles, grills or vents disposed around the rack's perimeter to supply sufficient cool air to meet its cooling requirements. Such a floor configuration would be difficult to achieve in equipment rooms crowded with racks and enclosures, and impossible to implement if racks and enclosures are arranged side-by-side in rows. Air cooling systems and methods that incorporate raised floor configurations, thus, are typically only used with racks and enclosures spaced apart to provide sufficient floor area to accommodate multiple open floor tiles, grills or vents. For typical rack spacing, this places a limit on the density of equipment that can be achieved. In addition, such air cooling systems and methods must supply cold air through open floor tiles, grills or vents to meet the cooling requirements of equipment having high thermal exhaust air output.
Equipment rooms and data centers are often reconfigured to meet new and/or different equipment needs that require individual racks and enclosures to be relocated and/or replaced. In this context, raised floor air cooling systems and methods are inflexible and can typically only be reconfigured and/or retrofitted to service rearranged, relocated and/or newly installed equipment racks at considerable cost. Raised floor configurations cannot easily and inexpensively accommodate the manner by which users typically deploy equipment racks and reconfigure equipment rooms and data centers to meet their new or changing needs.
In addition, cooling systems and methods that require raised floor construction lack physical flexibility and portability to operatively account for a wide variation in electrical power consumption between different racks and enclosures in an equipment room, and, in particular, between racks and enclosures located in the same row. Cooling systems and methods that rely upon raised floor air passageways and open floor tiles, grills or vents to supply cool air cannot easily and inexpensively vary or concentrate cool air to those high power racks that consume relatively large amounts of electrical power and have a high thermal air exhaust output. In addition, newly installed equipment may draw more electrical power than replaced or existing equipment to create thermal problem areas in functioning equipment rooms.
Further, cooling systems and methods that depend upon raised floor construction cannot physically accommodate specific areas in equipment rooms with thermal problems. For example, such systems and methods cannot overcome exhaust problems where hot and warm exhaust air is not effectively vented from an equipment room and/or returned to an air conditioning or cooling system without considerable expense to reconfigure and/or retrofit the air systems and/or the racks and enclosures. Such exhaust problems can also cause hot and warm exhaust air to recirculate to racks and enclosures, raising operating temperatures of equipment and, in particular, equipment with high power consumption and/or equipment located in areas of an equipment room with thermal problems. Similarly, raised floor cooling systems and methods cannot account for local thermal problems where hot and warm exhaust air from one rack is drawn into adjacent and/or proximate racks causing equipment overheating. Raised floor cooling systems and methods cannot easily retrofit to existing cooling systems of an equipment room or data center or to existing equipment racks.
Air cooling systems and methods that require raised floor configurations also reduce available headroom in equipment rooms and data centers. Wires housed within air passageways below raised floors are difficult to access. In addition, such air passageways are difficult to clean. Open floor tiles and floor grills or vents also pose a safety risk to personnel. In addition, raised floor construction presents a risk of collapse during earthquake.