Thermal Solutions for Servers Part 1

In this two part blog series, ATS gives an overview of the challenges and solutions in cooling servers that are used for cloud computing.

Part One – Aisles and Cabinets

A major issue with servers is the heat they generate and the heat that surrounds them. This heat has to be managed to ensure proper server performance. Even server installations with integral cooling systems may have to contend with higher power electronics or higher volumes of hot processors than they were originally designed for.

Server rooms, enclosures, racks and PCBs are all typically crowded, which poses challenges to cooling solutions at every level. And, in most cases, multiple solutions are needed. The good news is that for each of these applications, a range of cooling methods is usually available.

At the macro level these methods include cabinet positioning, ventilation fans, blanking panels to maximize cold air flow, portable air conditioning units, and skirts and barriers to direct cold air. At the micro level, liquid cooling integrated with heat sinks and spreaders provide effective chip level cooling.

Figure 1. Hot aisle/cold aisle room layouts are widely regarded as the starting point for heat management and energy efficiency in server rooms. [42U Data Center Solutions]

For server rooms, laying out hot aisles in between cold aisles has helped solve many heat issues and remains in common use. Typically, air from the hot aisles is captured by CRAC (computer room air conditioning) units, cooled, and then distributed to the cold rows via perforated flooring systems.

Portable air conditioners, such as the ClimateCab AC units by Black Box, attach directly to racks or enclosures to directly cool components. Many sizes of combined cabinet/AC units are available, including Black Box’s range of NEMA 12 server cabinets with M6 or tapped rails and various cooling capacities.

Figure 2. AC Units attached to server enclosures save money by cooling the cabinet and not an entire room. ([Black Box Network Services]

Server-filled data centers are often built as add-ons to existing facilities. The cooling system provided for these custom-added centers can be less reliable than the central HVAC installation, resulting in periodic down-times and longer-term outages. Portable air conditioners are available to provide extra cooling to heat sensitive areas during system outages or when extreme conditions occur. These units can protect equipment – and inhabitants – from overheating when the temperature demands exceed the capacity of a building’s climate system.

One example of these AC units is the Office Pro 63 portable cooler from MovinCool. This is a high end, high performance cooler. It provides 60,000 Btu/h cooling performance which can readily cool large spaces such as server/telecom equipment rooms. The Office Pro 63 has a programmable controller for continuous operation, and an automatic condensate pump.

Figure 3. The Office Pro 63 Portable Cooler Provide 60,000 Btu/h Cooling to Lower Temperatures in Electronic Equipment Rooms. [MovinCool]

MovinCool also produces the CM12, a ceiling-mounted packaged air conditioner. It fits into an existing drop-ceiling to save space in server rooms with limited floor space.

A range of specialty portable coolers can provide spot cooling in troublesome server hot spots. This capability can remove the need and expense of installing a permanent air conditioning system. These devices are economical and efficient, cooling only the area or object which must be cooled. Portable coolers require minimal installation, and are easily moved from one room to another. Cooling air is delivered instantly.

Figure 4. The 5KK30 Air-Cooled Portable Air Conditioner with 29,000 Btu/h Cooling Capacit]. [Koldwave]

For multiple hot spots, the air-cooled portable 5KK30 system from Koldwave delivers cooling air to different locations via three air flexible air outlets. The quiet-running unit is designed for ambient temperature is simple to install and operate. It has a cooling capacity of 29,000 Btu/h.

The engineers at TrippLite recommend the use of blanking panels to fill unused rack spaces. This forces cold air through equipment and prevents hot air from recirculating through open spaces. Snap-in 1U blanking panels install easily and the 1U size fills empty rack spaces evenly. Tripplite suggests installing brush strips, gaskets and grommets to block air leaks around cable channels and other gaps.

Another technological approach is the use of vortex enclosure cooling systems. These work by maintaining a slight pressurization inside a cabinet to keep electrical and electronic components clean and dry. Most vortex systems are thermostatically controlled to maintain enclosure temperatures within a specified temperature range.

The core of this technology is vortex tubes, mechanical devices that separate compressed gas into hot and cold streams. Air emerging from the cold end can reach -50°C, while air emerging from the hot end can reach 200°C. The tubes have no moving parts.

EXAIR Cabinet Cooler systems use vortex tube technology to create a cold air outlet flow which is pumped into an electronic cabinet. As air is pushed into the cabinet the Cabinet Cooler system also provides its own built-in exhaust so there is no need to vent the cabinet. This creates a positive purge on the cabinet which will keep out dirt, dust and debris.

Figure 5. The ETC Dual Cabinet Cooler System Minimizes Compressed Air Use and Produces 20F Air for Cabinet Cooling. [EXAIR]

Every server installation is unique, and from its components to its cabinets to its room environment there are likely to be heat issues. The above discusses some of the more common thermal solutions in use today at the aisle and cabinet level.

Ahead we will discuss cooling solutions for servers at the component and PCB level.  Click here to reach Part 2.



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