Getting Technical
CHARLES NICOLSON
Charles Nicolson has a physics and chemistry degree from Natal University which he subsequently put to
good use by applying speciality chemicals in mining and industrial processes where water is a major factor.
This created an enduring interest in water technology, a passion that expanded to the HVAC industry
in 1984 when he joined BHT Water Treatment. Since then, water technology in HVAC water circuits has
continued to be an abiding interest.
LOOKING AT ICE RINKS
By Charles Nicolson
Ice rinks use all three water phases during cooling, heating and
humidity control.
A
requirement for cooling as part of comfort air conditioning
in an ice rink seems, at first sight, to be a contradiction in
terms. The primary task of an ice rink refrigeration plant is to
create the ice and then to keep the ice sheet, or ice slab as it is
often called, cold enough to eliminate any possibilities of melting.
However, any building or enclosure where ice is the major portion
of the floor area is clearly going to become far too cold for
comfort unless interior temperatures and humidity are controlled.
Almost all modern ice rinks are enclosed or are a defined
section of a mall or shopping complex, which was taken into
account in the initial HVAC planning and design. Stand-alone
enclosed ice rinks may need cooling air conditioning particularly
for the rows of spectator seats that are more than 2m above the
ice level.
Movement of air in contact with or close to the ice tends to
be restricted to minimise ice/air heat transfer at the ice surface
where temperature control is maintained as accurately as is
practically feasible. Getting the surface of the ice “just right”
for both “sliding” and “chipping” characteristics in contact with
skate blade pressures is apparently reasonably straightforward,
but keeping it that way over the whole surface area of the ice
depends on having enough refrigeration capacity distributed
evenly under the ice sheet.
However, comfort conditions for both skaters and non-skaters
as well as spectators and other occupants of all levels of seating
provided have to be catered for without adversely affecting ice
surfaces. To achieve this, additional air handling and treatment
installations are needed, which will be looked at after considering
in more detail how the ice sheets are made and maintained.
How thick are these ice sheets? Probably a bit thinner than
is generally imagined. Ice thickness depends on what types of
skating and other activities a rink has been designed for. General
recreational skating needs a thickness of around 20-25mm,
but displays such as figure skating and competitive sports,
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particularly the major sport which is ice hockey, need a few more
millimetres to accommodate higher skate blade pressures as well
as “chipping” when the serrated curved front sections of blades
physically remove pieces of ice during stop/go or manoeuvres
involving quick changes of direction.
These relatively thin ice sheets need reliable support,
which is usually a concrete slab in which the cooling coils of the
refrigeration plant are installed. Underneath the concrete slab is
a layer of insulation such as asphalt, which in turn rests on a bed
of gravel laid on the base foundation of sand containing heating
pipes, if protection against ground frost is required.
ICE SURFACE
REF PIPE CONCRETE REF PIPE
INSULATION
GRAVEL
Figure 1:
Foundation and
support layers for
ice sheets.
FOUNDATION SOIL
HOW MUCH ICE NEEDS TO BE CREATED
AND MAINTAINED?
Sizes of ice rinks range from the small recreational rinks up
to areas with dimensions specified for events, once again in
particular for ice hockey, for which there are basically two
rink sizes in use, although there is a great deal of variation.
Historically, earlier ice rinks were smaller than they are today.
Official National League rinks are 26m × 61m. The dimensions
originate from the size of the Official Olympic/ International
rinks which are 30m × 60m.
RACA Journal I June 2019
51