PROJECT
INCORPORATING COLD CHAIN
Challenges of refrigeration system
for thermal test chamber
By John Ackermann
The construction of the chamber to test the thermal efficiency (K factor) of road vehicles
at the SABS in Pretoria, presented some unique engineering challenges to the refrigeration
contractor, Multistage Cooling.
T
he insulated chamber, with 150mm
of polyurethane, measures 20.3m (l)
× 4.4m (w) × 7.7m (h) and has doors
with a clear opening of 4.9m (h) × 4.0m
(w) at each end. A false ceiling provides
a space of 2.0m (h) × 17.2m (l) and the
full width of the chamber for the glycol
cooling coil, bank of induction heaters,
and five axial fans of 1 000mm diameter
with 2.2kW three-phase motors.
The dimensions of the chamber can
accommodate insulated/refrigerated
trailers, rigids, marine containers, and
tankers of maximum legal length, height,
and width. With doors at both ends, the
placing of the vehicle in the chamber is
done with ease.
Air temperature in the chamber is
maintained within a close tolerance by a
glycol cooler with mixing valve and bank of
induction heaters for reheating if required.
The test to validate the K value of
a vehicle is done in accordance with
standard SABS 1744. The standard
prescribes air temperatures, air speeds
and time intervals. Briefly, the test requires
maintaining the air temperature in the
chamber in the region of 7°C and the
interior air temperature of the sealed
vehicle heated to 35°C with electric
The package unit, built in the Randburg workshop of Multistage Cooling, was delivered to site on a skid.
The galvanised steel support structure was erected after the
blower coil had been placed in position.
Access to the coil, heater bank, and fans is gained from three
hatches in the roof via a ladder and catwalk.
Bob Vuletic of Multistage Cooling personally supervised the
installation of the equipment and refrigeration plant.
COLD LINK AFRICA • November | December 2017
www.coldlinkafrica.co.za
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