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Events and Exhibitions
• Unit technology and design versatility: Modern manufacturers offer a wide array of options, including air-cooled or water-cooled units, various compressor technologies( scroll, screw, centrifugal, on / off, stepless, inverter) and diverse design criteria such as high efficiency, low noise, specific dimension and redundancy. Different evaporator and condenser types( plate, shell-and-tube, copper, aluminum, microchannel) also play a role
• System versatility: Units can be configured for cooling only, heat pump functionality or advanced four-pipe systems( polyvalent units) for simultaneous heating and cooling, offering substantial energy savings. Six-pipe units for geothermal applications and systems incorporating heat recovery or free cooling( increasingly critical for the rapidly growing data centre sector) further enhance efficiency. Rossettini noted ASHRAE 9.9 ' s increased data hall temperatures( 25 to 27 ± 2 ° C) and the emergence of liquid cooling technologies as crucial developments for data centre efficiency
• Cost and available space remain practical constraints that must be balanced with efficiency goals
AVOIDING SHORT CYCLING AND THE IMPORTANCE OF WATER VOLUME " A critical factor for achieving high efficiency and extending equipment life is preventing short cycling— where chillers start and stop too frequently. When a chiller is turned on, it consumes input energy with zero output energy for a period as it ramps up. To achieve decent efficiency, a chiller should run for at least five, ideally 10, minutes before stopping. If a chiller is oversized for a low load and stops after only three minutes, its efficiency is extremely low, and its lifespan is significantly reduced."
To mitigate short cycling, Rossettini recommended designing with multiple, smaller units in parallel:“ Instead of one large unit, employing several smaller chillers ensures that when a chiller starts, it can run for a sufficient duration( for instance, 10 minutes) before the next one engages. This strategy alone can yield a 30 % gain in efficiency,” he said.
“ Maintaining sufficient water volume in the system is absolutely essential for several reasons.”
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RACA Journal I September 2025 www. refrigerationandaircon. co. za