Page 38 - Plastics News November 2019

FeAtures

compressors are used, but until recently they all operated the newest trend in central chiller system design is to
at one fixed speed. A relatively new technology is variable- combine the benefits of a variable-speed compressor with
speed compressors. With this technology, energy use is that of an adiabatic fluid cooler.These hybrid systems use
reduced by slowing the speed of the compressor to just an adiabatic fluid cooler to cool the condenser of the chiller
what is needed for the conditions. When the compressor during the summertime, but when the outside ambient
slows down, there is a reduction of cooling capacity. Most temperature is cool enough, the adiabatic fluid cooler
chiller system designs use the maximum possible heat load directly cools the process water, which means the chiller
at 100% production capacity of the process equipment to turns off completely. This saves 100% of the electrical cost
ensure there is always enough cooling capacity. In most of operating the chiller, which is the most significant power
cases, the production equipment is operating at much less consumption of any process cooling system.The number
than maximum capacity, so the chiller is ‘over-sized.’ A of hours of free-cooling increases when the process fluid
variable speed compressor is a great way to save this excess temperature is warmer. In many extrusion applications,
energy. Power use is a “square relationship,” meaning that the chilled water set point temperature is such that the
as the compressor speed changes, the power use changes as chiller may only need to run 50% of the year.
a square of the speed change. For instance, if a compressor
operates at 80% of its maximum
speed, it will use 64% of its full-
speed power. This technology
is available in a wide-range of
compressor sizes. In addition, the
initial equipment cost premium
for this technology, depending on
the hours of operating and load
profile, can pay for itself in 12
to 18 months. More on portable
chillers and central chillers.
Dramatically cut chiller
energy costs with free-
cooling systems.
Considering the ever-increasing
need for more efficient systems,

Plastics News November 2019 38