DATA CENTRES All meshed up
Sami Ure, business development manager Ecomesh looks at adiabatic cooling.
I
t can be said that data-centres represent without doubt one of the most demanding and challenging HVAC settings in our industry.
With an ever-increasing push to cloud-based computing and server space at an all-time premium, it is no wonder why this specific HVAC sector has seen exponential growth in recent years. Over the past nine months the world has
unfortunately been dealing with the terrible effects of the global COVID-19 pandemic. One of the major responses from across industries is the rapid push and transition to remote working and more advanced technological solutions. This quantum shift in global working patterns has only helped contribute to the increased demand on data-centres across the world. The future business landscape has been forever changed and it is in light of this dramatic rise in technology adoption, that those of us involved in the HVAC industry need to look for more efficient, effective and greener solutions to help facilitate this change. One such method to improving the efficiency of data-centre cooling applications, are ‘adiabatic cooling technologies’. This very simple concept is based on a millennium of human knowledge with regards the cooling benefits of passing air over water. With an effective adiabatic cooling system, it is possible to pre-cool the air passing into a wide range of HVAC machinery, ranging from chillers to dry-coolers, as well as both ammonia and CO2
systems alike.
By providing a cooler incoming air temperature to the condenser coils on this equipment, it allows for an artificially lower operating temperature. This lower temperature leads to improved compressor performance, greater energy efficiency and increased total capacity. Data-centres are able to save money, whilst also lowering their total energy consumption levels, hence helping to reduce their carbon footprint and impact on the global environment. With governments across the globe forever
looking for methods and incentives to help reduce global carbon emissions, it can be said that adiabatic cooling technologies represent a very useful tool at our disposal. In this article it is my
30 November 2020
aim to showcase a few of the key technologies that have established themselves at the forefront of this green adiabatic revolution. Evaporative condensers and cooling towers
were once seen as the best and most economical solutions to this approach, however they have come under increasing scrutiny and regulation in recent years as the risks of Legionella become ever-greater, if good maintenance is not ensured. Although well maintained cooling towers operate effectively, many sites unfortunately do not receive the adequate levels of maintenance to ensure safe operation. This is without a shadow of a doubt one of the primary reasons we can see a significant rise in the adoption of a number of alternative adiabatic cooling technologies such as plastic drift eliminators, rigid/paper mats, direct water spray on to the coils and various forms of fogging systems.
High-pressure water fogging systems have
been recently designed and installed as a method of cooling the condensing coils directly. Although this concept does provide efficient cooling, it has a multitude of glaring negatives. The water consumption for these systems is significantly high, enhanced further by the fact that the majority of the water is wasted. Secondly, because this system sprays water directly onto the aluminium and copper coils, advanced coil protection strategies need to be adopted, otherwise it is inevitable that scaling and corrosion will become a serious issue. The final disadvantage with this system is that because there is a requirement for highly atomised water, a UV filter or other form of water treatment must be installed to ensure a high level of water quality. When you combine a requirement for high quality water and the risk of a corroding coil, the level and cost of maintenance for these systems becomes so high that any energy savings you receive from the evaporative cooling have the potential to be wiped out. Another system designed to tackle the issue of high ambient is a wet-pad system. This design features cardboard/plastic pads placed directly in front of the condensing coil, water is then dripped throughout the pads, allowing for the adiabatic evaporative cooling to take place. Although this system uses less water than an atomised system, it faces a significant issue related to dust and dirt clogging the pads. Once this happens it is unfortunately the case that significant pressure
drop can arise, leading to decreased efficiency and eventual compressor shutdown. One further issue is maintenance; these pads require replacement on a regular basis, which removes the convenience / ease of use factor. The final adiabatic technology currently available is a mesh and frame based system, designed in such a way that the mesh protrudes away from the chiller coils at a 45 degree angle. This system sprays water at a low pressure of only 2 - 3 bar, away from the condensing coil and onto a purpose built plastic mesh. A second layer of mesh is installed along the back-side of the frame, in order to negate any potential water spraying back to the coil.
All of the evaporative adiabatic effect takes
place on the mesh material itself, cooling the air passing across and into the condensing coil. This system drastically reduces the risks associated with legionella by combining a total waste principle, no water storage and a low-pressure water spray. The mesh itself also acts as a self-cleaning filter through the adoption of a dual-layered mesh design, which in normal everyday use rub up against each other and break up and remove any calcium deposits or debris build up. This system is also designed to work in
conjunction with an advanced control management system, designed in such a way as to control water spray duration, frequency and generate flush cycles to avoid dead legs of water. It is vitally important to balance the adiabatic cooling benefits alongside total water consumption levels, as water wastage can lead to it’s own host of negative economic and environmental impacts. With the mesh and frame systems, the spray duration and frequencies are fully adaptive and capable of adjusting to the outdoor ambient temperature conditions. This allows for the mesh-based system to be incredibly effective and water efficient. The future of evaporative cooling has never looked stronger, with multiple companies and technologies being established yearly and the industry acceptance of the concept growing exponentially. We are all living through challenging times at the moment, however the future outlook remains positive and we are at an exciting time period for green driven HVAC efficiency. It is my hope that with increasing levels of competition and technology adoption, we can help push forward our sector and lead to yet further innovations and improvements.
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