Cold Link Africa March/April 2021 | Página 23

INCORPORATING COLD CHAIN
PROJECT
and by successful operation will result in it being rolled out to other sites throughout South Africa .
DESIGN SPECIFICATIONS AND RESULTANT STATE-OF-THE-ART COOLING SYSTEM
The design specification for the refrigeration system installed at the facility is an energy-efficient multi-temperature transcritical CO 2 system , designed by industry specialist Wynand Groenewald , that takes the important factors around global warming and environmental impact into account . Both Precool Cold Storage and Maersk strive for a minimal carbon footprint . CO 2 is one of the refrigerants of the future . The refrigerant
1 boosts a global warming potential of 1 , making it virtually climate neutral .
The resulting installation is a facility that can operate from ambient to -25 ° C , with a total installed capacity of 5.28MW through this transcritical CO 2 system . This consists of the following elements :
• Medium Temperature Capacity of 3 720kW @ various suction temperatures
• Low Temperature Capacity of 1 560kW @ -25 ° C
The refrigeration installation includes five transcritical CO 2 booster systems with parallel compression ( on four of the five systems ). Each system has an adiabatic gas cooler to increase energy efficiency .
© Cold Link Africa | Benjamin Brits
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5
© Cold Link Africa | Benjamin Brits
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© Cold Link Africa | Benjamin Brits
There is one system for the airlock , two
Heat-reclaim heat exchangers are
for the sterilisation rooms ( split over the
installed on the refrigeration racks to
two rooms for redundancy ) and two for
provide ‘ free ’ heat in terms of hot water .
the holding rooms ( also split over the two
400kW can be used for heating water
rooms for redundancy ).
from 20 ° C to 60 ° C , when operating at
Parallel compression was included as it
only 30 % of the installed capacity .
works alongside the medium temperatures
There is also a hot gas defrost function
and handles any flash gas that comes
for low temperature applications to
from the receiver vessel and makes a
reduce electrical usage ( instead of
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system more efficient because the gas is being handled at a higher evaporation temperature and the higher the evaporation temperature , the more efficient the compressors . Instead of dropping all the flash gas down to the evaporation temperature in the medium temperature system , parallel compressors are used .
The steri-rooms as well as the holding
electrical defrost ). Defrost is done by controller and defrost cycles occur at different times as there are quite a few fan coil units in each of the rooms .
Steri-rooms are included at the facility because they form an integral part of export produce and strategically allow Precool Cold Storage to accommodate as many
rooms were designed to operate as either
services as possible for the entire cold
chillers ( medium temperature rooms )
chain . Some countries require different
or freezers ( low temperature rooms ),
temperatures and different protocols
depending on the demand . The unique
that must be complied with in order to
design of the facility allows each individual
pass as export quality .
room to operate at the desired temperature
Most of the export products handled
without affecting any of the other rooms
by the facility come from the North
within the facility . Suction gas from the rooms
of the country and the new facility is
is diverted to the required compressor suction
both a DALRRD and PPECB approved
group to obtain the required temperature .
facility in the chilling of fruit and other
© Cold Link Africa | Benjamin Brits
1 . The de-superheater discharge unit ( to the left ), reduces the low temperature discharge temperature before it enters the medium temperature suction .
2 . Variable speed drives allow a soft start as well as the ability to run to the required capacity .
3 . One of the control panels installed in the refrigeration plant room . 4 . The refrigeration plant room at the back of the facility . 5 . The control panels for the facility .

COLD LINK AFRICA • March / April 2021 www . coldlinkafrica . co . za 23