Cold Link Africa January / February 2020 | Page 31

FEATURE
INCORPORATING COLD CHAIN
The versatility of ice banks
By Kevin Walter, mechanical engineer at Lutz Refrigeration
Aside from their popularity in the dairy scene, ice banks can be installed
in any perishable food application.
I
ce banks are a fantastic option where different. It was soon discovered that this
water temperatures needs to be as would be the largest ice bank we’ve ever
close to zero as possible without glycol produced so ensuring a quality installation
or any other anti-freeze being added.
was top priority. Scheduled to run for
These kinds of systems are found in five months, the project ran four weeks
facilities where water must be in contact over schedule and various unforeseen
with food products, for example, the challenges cropped up in the finishing
snap cooling of cherries, grapes and fruit straight, that were of course resolved.
Prior to installation, we bounced ideas
in general.
Ice banks have been around for as
around to meet the requirements, and
long as most people can remember. suggested adding salt to the water to try
They are particularly popular amongst and bring freezing point as low as -2°C.
dairies as they give the dairy the ability But in the end we erred on the side of
to generate ice all day long and when safety as the risk of corrosion on the ice
bottling or pasteurisation begins, they can coil was too high to justify the extra few
rapidly burn the ice off with an effective degrees of cooling.
cooling at the moment of magnitudes
higher than their compressor power SYSTEM INSTALLATION
would normally allow for. The system comprises of three ice coils
Awarded in February 2019, Lutz
each with their own compressor feeding
Refrigeration installed an ice bank at a into a split circuit evaporative condenser.
meat facility in the east of Johannesburg. Each ice coil is located within a common
The client sought to produce 15000 ℓ/hr tank and is monitored for ice thickness
of water at as close to 0°C as possible for individually, controlling the ice thickness
various meat cooling processes around between roughly 2mm and 12mm for the
the factory. This would equate to a water melt and build phases.
chiller duty of nominally 400kW.
Admittedly, every project comes
with its challenges and this one was no
The finished product.
The benefit to breaking the coil into
three sections is that the plant runs
in increments of 33/66/100% cooling,
depending on client demand. Generally
speaking, the plant seldom
runs more than two circuits
at a time while the other
circuits are in melt phase.
This keeps peak kVA usage
down and ensures that the
condenser is well-sized to
run the compressors at low
condensing temperatures
which is similar to a
multiplex/rack design
philosophy.
As with all installations
these days energy saving between traditional air- and water- when the tank gets to the scale of this
is critical. For this reason, cooled plant the difference in unit so we had headaches finding ways
traditional dry cooled Coefficient of Performance (COP) of controlling the ice thickness as the old
systems were replaced by improves from 2.6 to 3.5 (45°C tried-and-tested approaches could no
water cooled condensers condensing vs 35°C) resulting in 35% longer be leant on.
which are oversized more cooling per kW/hr electricity used. Additionally, the concept of an three compressors at ice bank gives the flexibility to make ice (4km total internal pipe length) as well
extremely low condensing outside of peak tariff periods and melt ice as an Evapco cooling tower and Plant
temperatures. This during the peak periods for your cooling. Skid with all compressors, switchgear
combined with electronic This takes strain off the electrical grid and and controls onto a site which was
expansion valves allows for moves the client’s energy usage out of basically populated with no space
condensing temperatures the more expensive tariff windows. allowed for this unit. We investigated
hot days.
To make a quick
and easy comparison
The ice built on the pipes.
January/February 2020
Space became an issue as we had to
to be able to run all
to be below 35°C even on
COLD LINK AFRICA •
Some of the pipework that feeds the system.
MEETING CHALLENGES
squeeze an 8000ℓ tank with stainless coils
building mezzanines above the electrical
DB room which was going to be very
To elaborate on these challenges, difficult with regulations and so on, and
structural requirements on tank design eventually had to opt to build a plinth
as well as ice build control systems remotely and pipe the chilled water over
become exponentially more intricate a bridge over the road.
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