Keep cool

Enclosures manufacturers are facing increasing problems with heat dissipation that call for innovative solutions.

As computers become faster and more powerful, increasing temperatures can dramatically shorten the working life of components. In the long term, heat generated from compact server rack systems can no longer be kept under control using standard air-cooling. This is why the fastest processors available have not been installed in compact servers until now.

One solution is the Liquid Cooling Package (LCP) from Rittal. LCP is a climate-controlled package fitted to the side panel of the server rack to solve the problem of high heat losses by providing scalable cooling using air/water heat exchangers.

Key advantages for the user include even distribution of cold air, unrestricted accessibility, plus the investment safeguards of a scalable system.

When cooling air is routed through an enclosure, the devices on the uppermost levels often lose out.

This problem is avoided by the LCP package which is installed to replace the side panel of an enclosure, or alternatively one side panel each of two adjacent enclosures. It accommodates, without restricting later expansion, one, two or three air-water heat exchangers, each with a cooling capacity of 4–8kW (and an air-flow rate of 700cu metres/hour).

This airflow is directed horizontally, immediately across the front of each server row, and ensures equal thermal conditions from top to bottom of the enclosure.

The closed-circuit cooling guarantees perfect functioning even in warm rooms, placing no additional load on the room’s air-conditioning. The water circuit can be connected to a re-cooling system by way of quick-lock couplings. Intelligent condensate management is also integrated.

Another advantage is that no installation space for active components is lost within the enclosure, and the side installation maintains accessibility of the 19in level over its full height, from both front and back. Each module has its own controller, which can be integrated into a monitoring network via Computer Multi Control (CMC) as appropriate.

This problem of overheating was experienced at the Max-Planck Institute (MPI) for biophysical chemistry in Göttingen, until it installed what is claimed to be the world’s first liquid-cooled server enclosure.

Among other things, MPI works with a 3D Kryo-electron microscope, which examines the structures of biological macromolecules. Currently, the 3D structure is calculated from 10,000–40,000 images. To be able to produce even more precise results, up to 500,000 images per molecule are necessary, needing enormous computing which, in turn, requires intense cooling.

‘Adding even more conventional systems would be very expensive and pushed us to our financial limits as well as taking up valuable space,’ said Dr Henry Stark, head of the MPI working group. ‘Liquid cooling appeared to be the most suitable way out of this dilemma and we had more or less taken the decision to develop such a server enclosure ourselves until a visit to CeBIT in spring 2002 saved us the anticipated long and costly development.’

On Rittal’s stand was a working, liquid-cooled IT rack, which was filled with industrial PC ATX racks. Around six months after the initial discussions, Rittal installed a server rack tailored to meet the high requirements of MPI. Thirty-four dual Athlon mainboards with their combined computing power will decisively increase MPI’s future image-processing capacity.

Heat sinks fitted on the central processing unit (CPU) are responsible for the immediate heat dissipation at the precise point where it occurs. Incoming and outgoing pipelines have been integrated into the enclosure, and to ensure a specific supply of liquid, are interconnected with an external, central re-cooling unit. Rittal’s Computer Multi Control (CMC) module provides additional safety by monitoring the incoming and outgoing nominal and actual water temperatures and flow-rate.

An alternative solution has been developed by American Power Conversion (APC) that incorporates a horizontal airflow design. Horizontal cooling provides a uniform curtain of cool air across the front of each piece of IT equipment regardless of its position in the enclosure. The horizontal airflow design differs from bottom to top cooling methods, which introduce the risk that equipment installed at the top of the rack will not get adequate cool air.

The system offers hot-swappable fans to ensure continuous operation and also includes an easy-to-replace cooling coil cartridge that lowers maintenance and service costs. This high-density offering not only gives IT managers the ability to accommodate increasing power and cooling needs, but also offers them the ability to deploy a solution to high-density issues in days without traditional requirements for data centre space.

‘As manufacturers continue to reduce the physical size of their technology, more equipment can be housed within the same cabinet, causing higher power requirements and more heat dissipation,’ said APC UK manager Michael Adams.

‘These new technology applications are leading to the creation of dangerous hot-spots within data centre racks. This innovation provides up to 15kW of cooling in a single enclosure, solving space constraint issues and giving users the ability to consolidate their IT equipment.’

According to Peter Furrer, IT head at Swiss F1 racing team Sauber Petronas, APC's High-Density Cooling Enclosure proved to be the ideal solution to Sauber's high-density cooling issues. ‘We were planning to deploy additional IT equipment that required us to power, protect and cool up to 15kW per rack,’ he said.

‘Our options were to either spread out the load, taking up valuable floor space, or find a solution that could effectively cool these high-power densities. The High-Density Cooling Enclosures have allowed us to deploy an independent, secure environment into our existing environment in only 10 racks without having to build out additional data centre infrastructure.

‘The solution enabled us to cool our high-density loads in the smallest footprint possible, giving us tremendous installation flexibility and providing the level of protection and availability we required.’

The High-Density Cooling Enclosure uses chilled water, the most effective and environmentally-friendly way to reject heat. The water is contained in an isolated cooling circuit, eliminating leaks. The system's doors are mechanically locked for security purposes and can be opened only with smart cards. An easy-to-use user interface display is located on the rear of the rack, allowing operators to control and monitor the system.

Additionally, an integrated visual alarm provides warning of critical conditions such as fan failure, leak detection and temperature problems.

With the density of power components in every kind of electronic device, these and future innovations will be needed to keep control of the extra heat generated.