ACR Journal

CMYK / .ai CMYK / .ai CMYK / .ai acrjournal.uk 19 ADVERTORIAL oxygen, proper maintenance of all equipment in the loop is critical. This also heightens the importance of water or fluid filtration and treatment. If the process water in the basin of the open tower is not properly treated, filtered and maintained properly, the energy efficiency of the system will be reduced over time due to scaled and fouled heat exchangers and chiller tubes. Open-loop cooling tower with heat exchanger An open-loop cooling tower is the best option for heat rejection in many applications. Facilities that are not facing the need to minimise water consumption may benefit from this type of system, as would a property needing to maximise the amount of heat-rejection capacity in a limited mechanical footprint. For the fluid’s process heating and cooling loops, however, a closed-cooling circuit is recommended. In these situations, isolating the cooling tower from the process loop through the use of a heat exchanger may provide an optimal solution. In this way, the benefits of a cooling tower can be provided without requiring the maintenance that an open- loop cooling requires. Isolating the system from the cooling tower through the use of a heat exchanger also eliminates concern for where the heat-rejection equipment is installed with respect to the cooling loop. Plate-and-frame heat exchangers are used most frequently for this type of design. When a heat exchanger is installed, the cooling tower must be sized properly to accommodate the temperature difference between the cooling tower water entering the heat exchanger and the process water that exists within the heat exchanger. Isolating the cooling tower with a heat exchanger will substantially reduce the need to maintain downstream components. This also means that the heat exchanger will require routine maintenance. To ensure that both the thermal performance and the pressure drop across the heat exchanger meet design requirements, heat exchangers should be certified per AHRI Standard 400, or a local equivalent such as Eurovent. Closed-loop technology Most cooling tower manufacturers offer a range of closed-circuit coolers – or as they are called, fluid coolers – to provide a heat-rejection alternative for engineers or end users who want (or need) to reduce water consumption and equipment maintenance. Some cooling applications require a closed-loop system for peak efficiency long-term operation. These types of systems generally include the use of small heat exchangers in terminal units or other connected equipment, making maintenance complicated, if possible at all. For example, buildings with water- source heat pump loops – widely used for healthcare facilities as well as office, hotel, high-rise residential buildings – are among one of the largest markets for fluid coolers. Using an open-cooling loop could pose the significant risk of fouling hundreds of heat exchangers in a condominium or similar facility. Closed-circuit systems are also prevalent among high efficiency chiller applications, data centers, battery plants, grow room facilities and multiple types of industrial process loops. Water loss through evaporation is either reduced or eliminated, depending on the type of closed loop cooling equipment selected. The most prevalent type of large-scale heat- rejection equipment in use today is the open-loop cooling tower. Wide available capacities and configurations, reasonable first cost and energy efficiency are features of open-loop cooling towers. In a dry cooler, heat from the process-loop fluid is transferred to the coil tube surface and out to the fins.