The global energy infrastructure is embracing digitization as offshore drilling rigs, shale platforms and refineries realize the importance of replacing simple pressure gauges and flowmeters with digital sensors and high-speed communications networks to move real-time data back to headquarters.
While new technologies are improving safety and productivity, the industry quickly is realizing the numerous failure points that make legacy technologies unsustainable for upstream facilities. Oilpatch computing systems require hardening to survive extreme temperatures, salt air, dirt and other pollutants. Additionally, every kilowatt-hour of electricity converted to heat needs to be dissipated and the waste energy recycled.
The traditional method of cooling electronics by circulating air around and through components achieves none of these objectives. Fans used to circulate massive amounts of air waste energy and expose computing equipment to corrosion and air pollutants. Mechanical refrigeration systems to maintain humidity levels and cool equipment in hot weather conditions require maintenance and waste even more energy.
Liquid cooling, if applied intelligently, can be an ideal solution, but not every approach to liquid cooling is applicable to oil and gas industry conditions. Cold plates, which are water kits installed directly on processors in the computer chassis, do not save much energy and invite trouble when a leak occurs. Cold plates were developed to move heat away from hot chips but only use liquid to remove some of the heat. Fans still are needed in the computer chassis to finish the job. The pumps, fans and heat exchangers in each computer case are subject to failure.
Other cooling solutions meant for extremely high-density systems involve refrigerants that remove heat by evaporation. This refrigerant vapor then needs to be condensed. These two-phase systems add complexity and cost and do not add much value unless rack power densities exceed 100 kW.
If the thermal load is less than 100 kW per rack, a single-phase cooling system where all electronic components are submerged in a nonconducting dielectric liquid is a viable alternative. This technology decouples electronic components from the environment and offers a long list of important benefits for oil and gas applications. There are no moving parts or heat exchange barriers in the information technology (IT) device chassis; electronics are isolated from oxidation and air pollution; there is no noise, vibration or extreme temperature fluctuation; fans and mechanical refrigeration are eliminated; there is no need for humidity control; and heat is recovered in a convenient form for recycling.
When considering total immersion systems, there are three main considerations: scalability, maintainability and cost efficiency. The devil is in these details.
There is a system on the market that resembles a rack tipped over on its back with modified servers inserted vertically into slots in the tank. The tank is filled with a coolant similar to mineral oil. This approach requires a relatively large amount of floor space, which limits mobility and scalability in a multirack environment, and the system is not fully sealed, which leads to fluid contamination in certain environments. Moreover, the system is heavy and must be assembled in the field, making its deployment for most oil and gas applications expensive, time-consuming and logistically challenging.
Yet another version includes off-the-shelf motherboards, which are mounted inside sealed hot-swappable cartridges that are flooded with a dielectric fluid. There is a secondary circuit with water snaking through a channel inside one wall of the cartridge to transfer heat from the dielectric fluid. This two-circuit approach adds cost, introduces water to the white space and interferes with maintenance.
The third version of total immersion combines a sealed enclosure and standard-size rack, an approach that places special emphasis on scalability. Additionally, the design makes it possible to cool any electronics, not just servers. By placing special emphasis on equipment maintenance and rack management, it is possible to hot-swap a rack-mounted IT device in less than two minutes without any loss of fluid.
The introduction of immersion liquid cooling technologies has been delayed by a perception that the equipment is expensive, difficult to maintain and messy.
Examining the myths:
- Cost. As long as liquid-cooled IT devices are manufactured a few at a time, they will cost more than air-cooled devices that are produced by the thousands. In fact, immersion cooling systems have no moving parts in the IT device chassis and, if properly designed, could cost less to manufacture when produced in volume.
- Maintenance. Fans are the root cause of most IT equipment failures, either because the fan itself fails or exposure to air causes electronic components to degrade. Eliminating fans reduces the amount of maintenance required. Additionally, rack-based immersion systems generally are designed to hot-swap devices quickly.
- The mess. In immersion cooling, electronics touch liquid, which is why this technology reduces the power to cool by more than 90%. So there will be some residue when an IT device is removed from a rack. However, proper maintenance procedures eliminate any mess.
When comparing the value proposition with legacy air systems or other forms of liquid cooling, immersion cooling saves energy and space, enhances reliability, operates silently and is easy to maintain in the field. Immersion cooling systems also simplify upgrades because there is enough cooling capacity in the chassis for future heat loads and only the internal boards need to be changed. Immersion systems cost less too, both up front and over time.
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