FEATURE
INCORPORATING COLD CHAIN
Refrigerated warehousing and
storage – refrigerants matter
By Ilana Koegelenberg
COMPARING SYSTEMS
With so many different options when
it comes to refrigeration solutions for
cold stores, how does one choose
the right system for your project? It will
obviously depend on the type of product
being stored, but there are also other
considerations.
Shane Moodley, cold store manager
at Go Chill (part of the Go Global group)
in KwaZulu-Natal, explains that plant
downtime and ammonia leaks are their
biggest concern as the client. So, what
do they look for in a refrigeration system
when setting up a new cold store? “It must
be user-friendly and friendly towards the
environment, as well as compatible for our
industry,” he says. “Also, it must be able to
handle the cooling when the cold store is
running at full capacity.”
Grant Ford of Matador Refrigeration
explains that the following are usually
considered before selecting a
system: energy savings, eco-friendly
requirements, and how user-friendly it
must be. Then the usual requirements:
insulation thickness, size, lighting, access
(manual, forklifts or trolleys). Also, airflow is
critical to achieve constant temperature
throughout the room.
Humidity required depends on product
requirements and things like fast chilled
versus slow chilled also makes a huge
difference. For example: potatoes need to
come down at 2°C a day to avoid them
going glassy when warmed up. “It’s crucial
at all times to avoid having the product
integrity compromised,” says Ford.
According to Ford, the consideration
taking place when choosing a system
nowadays is linked to:
a. Mechanical systems:
i. Simplex – single compressor
application
ii. Multiplex – multi compressor
application
b. Or chosen by refrigerant:
Hydrocarbons, ammonia, CO 2, or
synthetic refrigerants.
c. A multi-rack also provides a more
controlled temperature range.
As mentioned, one of the main
considerations for selecting a system
relates to the refrigerant used in the
system. HFC refrigerants are still the most
common solution (and cheapest) but as
the imminent global phase-down starts
taking effect, many are looking at more
natural alternatives such as hydrocarbons,
ammonia, or CO 2 systems.
Christo van der Merwe of Marine and
Refrigeration Engineering (MRE) explains
that the most common systems are as
follows:
• Ammonia systems
Industrial ammonia is the most appropriate
system for large installations and has the
best coefficient of performance (COP)
available. These systems are designed for
a 30-year or greater life span and offer
excellent reliability if maintained correctly.
For the smaller sized cold store installations,
the first costs can be considerably higher
but over a 20-year life cycle costing,
which takes into account the total
operating cost, the ammonia option can
be an interesting proposition.
• CO 2 cascade systems
CO 2 is established as a preferred ‘green’
solution for supermarket applications
and is being considered for certain low
temperature applications such as freezer
stores. CO 2 (sub-critical) cannot match
the COP of ammonia plants though. CO 2
(trans-critical) COPs are just starting to
match typical air-cooled R404s COPs and
the higher ambients in South Africa must
be taken into account when evaluating
the total operating costs of this solution.
• R404a, R507, and other HFC cocktails
Air-cooled synthetic refrigerant systems
omeone once told me that no
matter how bad the economy
gets, people still need to eat. And
with more and more people moving
to cities, the role of the cold store is
becoming more critical than ever
to ensure there is enough perishable
product where it’s needed most. So,
despite many HVAC projects being put
on hold and the state of the industry
being described as ‘sluggish’ at best
when it comes to projects, cold stores
are still going up left, right and centre.
A vital link in the cold chain, the cold
store is crucial for ensuring perishables
make it to their fiinal destination in the
best possible condition. But not all cold
stores are equal and it seems the key
distinguishing element has become the
refrigerants used in the refrigeration plant.
Are natural refrigerants the way forward?
We speak to the local stakeholders to find
out more.
Hydraulically operated dock levellers operate much faster and more reliably than their air-
powered counterparts.
S
We chat to the professionals about all things cold storage – from selecting your refrigeration
system to maintenance, and local trends in the market. What are the dos and don’ts of refrigerated
warehousing and cold storage?
The size of the cold store will influence which refrigeration system should be selected.
are the correct solution for small cold
storage applications, typically up to 150
or 200 pallets of frozen storage. These
systems have a lower first cost but the
running costs are higher (due to a low
COP and high electrical costs) and often
the maintenance costs can be higher
due to low quality installations with gas
leaks and equipment failures.
Marius la Grange of Energy Partners
Refrigeration Solutions, who is also
the current South African Institute of
Refrigeration and Air Conditioning
(SAIRAC) national president, goes into a
bit more detail.
Consider a distribution centre (DC)
application. It’s important to calculate
the medium temperature (MT) load
COLD LINK AFRICA • July/August 2019
required compared to that of the low
temperature (MT), advises La Grange. The
COP of the LT load is significantly worse
than MT applications, regardless of the
refrigerant used. “That is an important
ratio to consider when comparing one
installation with another.”
HFC installations are the most common,
with the refrigerants being selected based
on the planned operating conditions,
explains La Grange. These offer a lower
capital outlay but with higher operational
cost (energy consumption). They are also
fairly simple to install in a relatively short
time period. “The long-term premium
is of course the energy consumed to
keep them running and there is not
much one can do to make them more
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