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SUPERMARKET SYSTEMS AND EQUIPMENT
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 3.5 bar, away from the condensing coil and onto the 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 spray back to the coil. All of the evaporative effect is generated along the mesh material itself, cooling the air passing across and into the Chiller.
This system reduces the risks associated with legionella by combining the total waste principle, no water storage and a low-pressure water spray. The mesh itself also acts as a self-cleaning filter, by combining a dual-layered mesh design, which rub up against each other and break up any calcium deposits or debris.
This system is also designed to work in conjunction with an advanced control management system, designed to control water spray duration, frequency and generate flush cycles to avoid dead legs of water. The future of evaporative cooling has never looked stronger, with
multiple companies and technologies being established yearly and the industry acceptance of the concept with regards to Chillers is growing exponentially. We are at an exciting time period for HVAC efficiency and hopefully
the increasing levels of competition can spur yet further innovations and improvements.
www.acr-news.com
April 2020 29
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