Of all the major aspects that keep a Data Centre running at optimum levels, controlling temperature is often considered a low priority compared to other functions and is therefore often ignored until a problem arises. Due to the crucial impact of temperature on highly sensitive and high-powered equipment, having an efficient and effective cooling strategy is an essential aspect of Data Centre operations. The method of cooling equipment inside a Data Centre has always been a critical element in the design process. Today, however, server room managers have a greater opportunity to reduce costs and increase equipment reliability while supporting increasing IT demands. To meet ever-increasing demands, Data Centres are now being designed to grow with the needs of the business. This includes the cooling system, which is designed to allow customisation.
At DCNART, we take the subject of cooling optimisation very seriously and build systems in such a way that they are both suitably scalable and efficient and energy-efficient. When selecting solutions, we take the following aspects into account, among others:
Water cooling systems use large chillers to produce cold water to cool the supply air. The chilled water is pumped to the CRAHs in the server room, while the heat is transferred to the cooling tower via condenser pipework. Chilled water systems are typically used in Data Centres with high energy loads of 200kW and above and moderate to high performance requirements. In many facilities, chilled water systems are often used to cool entire buildings, even if the Data Centre uses only a small proportion of the total cooling capacity. In the past, water cooling was often chosen for large, multi-storey facilities, mainly because it was more efficient and, due to the size of the facility, cheaper.
Air-cooled systems are two-part designs that include an air-cooled CRAC system and a condenser, which is also known as a CRAC DX (direct expansion) system. Air-cooled CRAC units are commonly used in Data Centres and are considered the norm for small to medium-sized server rooms. In this type of system, refrigerant circulates in tubes between the indoor and outdoor components. Heat is transferred to the outside by means of circulating refrigerant flow. Stand-alone air-cooled systems are air-conditioning units that are connected in air ducts. Typically, these systems have all the components of the refrigeration circuit in one housing. Heat escapes from this system as an exhaust air stream that is directed from the IT rooms to the outside of the building or to specific rooms that do not require air conditioning.
As Data Centre cooling technologies have developed and become more advanced, and as the heat load on server rooms has increased, other more efficient technologies have gradually displaced DX systems. Nevertheless, DX systems are still a frequently used solution. They are now configured to use a heat exchanger. However, this requires the installation of additional hardware along with cooling units, which increases the cost of the system.
The term free cooling refers to the ability to cool the Data Centre without the use of a refrigeration circuit. Energy-consuming pumps and fans continue to operate in these systems. Free cooling uses local ambient conditions to cool the supply air supplied to the IT equipment.
There are two main types of freecooling systems:
Outside air is brought into the Data Centre directly through filters or indirectly through heat exchangers. In air-based systems, outdoor air filtration plays an important role as a contamination prevention factor and also as a humidity control tool.
This system uses refrigerants, such as water or a water-glycol mixture, which circulates directly through cooling towers and/or condensers instead of chillers or compressors. Water-cooled systems separate the outside air from the inside air, providing cooling through a heat exchanger. Depending on the location of the Data Centre, it is possible to use cold water from rivers, lakes or oceans instead of using traditional closed water cooling systems.
There are various approaches to liquid cooling. The two main ones are either to supply liquid to the server itself via a closed system, consisting of tubes and plates, or by immersing the entire server chassis in liquid. One of the challenges of liquid cooling is the high initial cost associated with it. This is a reason why, many Data Centre managers are likely to avoid this method. Another concern is the liquid itself being near valuable IT equipment. This is something that is generally avoided, so there are some negative views on this solution.
Rotary heat exchangers have been around for years, but recently they have been increasingly used in Data Centres. These exchangers are constructed from aluminium hexagons. Hot air from the servers is drawn into the heat exchanger by fans. The exchanger absorbs heat from the air that flows through it. The cooled air is then sent back to the data centre. In a separate airspace, outside air is drawn into the cooling unit by fans, passes through the heat exchanger, absorbing heat and discharges it back outside. The wheel of the heat exchanger rotates between the air spaces (outdoor and indoor) to efficiently transfer heat. Cooling systems with wheel heat exchangers are efficient and provide an indirect cooling system. They are installed in a variety of environments around the world. One disadvantage of the circular heat exchanger is the amount of extra space, which generates additional costs, in the event of excessively high outdoor temperatures where conventional cooling is required.
