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PROCESS COOLING


CLIMATE OFFERS ENERGY SAVING OPPORTUNITIES


CLIMATE OFFERS ENERGY SAVING OPPORTUNITIES


Angus Hall, business line manager, Atlas Copco Process Cooling Solutions, explains how an innovative cooling/chilling system can improve manufacturing costs, lessen environmental impact, and help industries realise energy savings


a water-cooling system. But in meeting these needs, what is not always factored in is the potential opportunity to reduce the running costs of energy, water treatment, and water supply involved in the process. The traditional approach to industrial


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cooling is refrigeration. That usually means employing big chillers of a megawatt and beyond in capacity. For many applications, this may prove to be an expensive-to-run solution that is not always necessary and isn’t the only answer. It pays plant managers and finance teams to investigate a solution that will reduce chiller usage and improve the efficiency and energy consumption of their cooling and chilled water systems – namely, a centralised adiabatic and free-air cooling installation. A concept that generates plant efficiencies, realises energy savings, and minimises environmental impact.


Take advantage of the climate One of the ways to help achieve that aim is to take advantage of our temperate British climate. Met Office data shows that for 50% of the year, the average temperature is less than 10˚C − and that is beneficial for the optimum energy-saving process cooling proposition: simply, that it is not necessary for 24/7 cooling operations to depend on chillers alone 100% of the time. Dependent upon the process, a


50 NOVEMBER 2022 | PROCESS & CONTROL


n a wide variety of manufacturing operations, there is a need for process heat and for a means of reducing that heat with


correctly designed and balanced smart system utilises adiabatic coolers with bridge heat exchangers in the cooler/cold periods of the year and energy-efficient chillers in the warmer periods, thereby taking full advantage of ambient conditions to reduce running costs. Basically, it comes down to differing levels of


power consumption. A chiller needs energy for the compressor and the refrigeration circuit, whereas a cooler only needs sufficient energy to power the cooling fans. A simple analogy is to think of a chiller as a refrigerator and a cooler as being a vehicle radiator that operates through airflow. Across industry the required process cooling


temperature may vary widely. Pharmaceutical applications may operate at 10˚C, a commercial bakery’s need can be for a continuous 15˚C, and a distillery’s process will be in the region of 20˚C. But within the plastics industry, a case study of one specific application that requires multiple temperature levels clearly demonstrates that the energy efficiency of a process cooling system can be maximised by a combination of chillers and coolers when ambient temperatures allow. In this instance, the plastics manufacturing


company’s injection moulding operations required a process water cooling circuit in the region of 25-30˚C for the critical granule feed throat and 7-24˚C to enable the mould tool to be at the right temperature for cooling the plastic items to be released from the mould. At the same time, the hydraulics actuators


involved required cooling between 10-18˚C. In addition to two large chillers, adiabatic


coolers were employed for both elements of the process. This was achieved by bridging the mould and hydraulic cooling circuits with a packaged heat exchanger unit, facilitating energy transfer without compromising circuit integrity. In a transition period when the ambient


temperature goes above 10˚C, a chiller is needed to maintain the desired level. During low ambient temperatures, the combined system of this type can use the surplus capacity from an ambient cooling system, such as cooling towers, air blast, or adiabatic coolers, to pre-cool water returning from the chilled water circuit before it reaches the refrigeration plant, reducing the amount of energy that needs to be consumed. Whilst the circuits continue to function normally, the chiller plant is less utilised, extending the life span of its components, reducing the cost to the environment, and achieving significant energy savings.


Adiabatic coolers The relative humidity of the air in the UK is 40 to 60% most of the time. Adiabatic cooling systems remove heat by evaporating water in a stream of warm, low humidity air. In the process of transition from a liquid to a gas, the evaporated water simultaneously humidifies and cools the air stream to within a few degrees of the wet-bulb temperature.


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