Feature Cases & enclosures
Keeping cool in mission critical situations
Electronic systems today are increasingly power intensive, and if a cooling system suffers critical permanent failure, this can result in shutdown or failure of the electronic components. As a result, manufacturers are developing cooling technologies that offer redundancy to eliminate such problems. John Wilkins of Rittal looks into the technology
oday’s electronic systems are increasingly power intensive and therefore liable to require increased heat dissipation. As with all electronic components, an optimum temperature and maximum temperature for operation exists, and it is the latter which can be the most problematic. Mistakes, most of which are avoidable, are routinely made when installing cooling systems that can compromise availability.
T
Critical electronic components are normally designed with a protective function which, when triggered, will automatically shut down the system to protect against high temperature damage. In a ‘stand alone’ mission crit- ical system, this could be disastrous. The design of any electronic system needs to allow a fail-safe delivery of thermal management and should take into account the cooling requirements to protect against any high tempera- ture damage and possible loss of system operation.
Despite design engineers allowing for cooling reserve – which involves the underrating of the electronic equipment in relation to cooling capacity installed – in cases where a cooling system suffers a critical permanent failure, a lack of redundancy results in the shutdown or failure of the electronic components. Such a shutdown could have catastrophic results, especially in environments where the systems oper- ated are mission critical. However, even when heat removal has been considered at the design stage of a project, it is statistically probable that at some point
When designing a cooling system for deployment in a mission critical environment, it is advisable to include a redundant cooling system
a component failure may occur. Cooling down
Circumstances such as these have driven manufacturers to develop cool- ing technologies that offer redundancy which should eliminate the possibility of a critical permanent failure These systems are ready to compensate if a cooling component fails – if, for example, a fan fails, a cooling system should immediately balance the loss by accelerating other operational fans, or energise unused redundant fans. When designing a cooling system for deployment in a mission critical environment, it is therefore advisable to include a redundant cooling system to ensure backup in case of a compo- nent failure. However, redundancy within integrated cooling solutions, such as liquid cooling, is often one of the most difficult areas to address, as there is seldom room or budget to install two of everything. To cool individual ATCA (Advanced
Telecom Computing Architecture), shelves containing numerous electronic boards, fan units can provide over 3.2kW of cooling (200W per slot), whilst offering reassuring safety features such as automatic restart, dual power input, hot-swap, and over- temperature alarm. It is also recom- mended that the blower incorporates a full speed function that can be activated if a failure is detected (Rittal’s Ricool II has this functionality as standard). With rising integration densities at all levels and higher clock frequencies,
Instrumentation FEBRUARY 2011
even higher heat losses are to be expected in the future. Innovations in thermal management such as liquid cooling of ATCA boards via CPU cooling or heat pipe concepts are among solutions for effective cooling of hot spots, ensuring reliable dissipation of up to 70% of the heat loss. A combi- nation of blower and direct chip cool- ing can provide cooling redundancy, offering users total security. Where a number of ATCAs are utilised, such as populating a 19” rack, direct chip cooling can be used in tandem with other active cooling components such as air-water heat exchangers. In this configuration, water is piped from a remotely and often externally located water chiller, itself often designed with a redundant pump and compressor for continuous opera- tion in the event of critical component failure. The cooled water from the chiller is fed via drip-free connections to both the CPU sinks embedded in the PCB, and the exchanger systems integrated within the 19” rack. This type of water-cooling system can provide over 30kW of cooling for all electronic components and provides a quiet option compared to more conventional air-cooling. The high rates of flow demanded of air cooled systems is not a requirement when using water, as exchanger fans can gen- erally be run at low speeds and direct CPU cooling has no fan requirement. Reliability depends not only on the quality of the components and the design, but also whether the equipment is maintained within its design parame- ters, particularly temperature. Properly cooled systems generally increase the MTBF (Mean Time Between Failures) of critical components.
Considering the technology It is evident from past experience that system components do and will continue to fail. In the instance that a failure takes place with either the con- ditioned system or the conditioning system, the impact on the user in terms of system availability and lost revenue can be quite substantial. To avert such situations and to allow timely repair, without lost operation time, the design of the complete system should incorporate emergency cooling and redundancy in line with the criticality of the system’s purpose. A failure to consider the correct level of emergency cooling can result in a disproportionate level of loss.
Rittal T: 01709 704000
Enter 687 23
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56