CO2 REFRIGERATION SYSTEM FOR ICE-PLAYING SURFACE

SYSTEME DE REFRIGERATION CO2 POUR SURFACE DE JEU GLACEE

English Abstract

A CO2 refrigeration system comprising a transfer
circuit for heat exchange between a supracompression circuit
of CO2 refrigerant, and an evaporation circuit of CO2
refrigerant. A transfer circuit absorbs heat from the CO2
refrigerant of the evaporation circuit, and releases heat to
the CO2 refrigerant of the supracompression circuit. The
supracompression circuit comprises a compression stage in
which CO2 refrigerant is compressed to at least a
supra-compression state, a cooling stage in which the CO2
refrigerant from the compression stage releases heat, and a
pressure-regulating unit in a line extending from the
cooling stage to the evaporation heat exchanger to maintain
a pressure differential therebetween. The
evaporation
circuit receives CO2 refrigerant having released heat in the
condensation heat exchanger. The
evaporation circuit
comprises a condensation reservoir in which CO2 refrigerant
is accumulated in a liquid state, and an evaporation stage
in which the CO2 refrigerant from the condensation reservoir
absorbs heat to cool an ice-playing surface, to then return
to one of the condensation reservoir and the condensation
exchanger.

Claims

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CLAIMS:
1. A CO2 refrigeration system comprising a transfer
circuit for heat exchange between a supracompression circuit
of CO2 refrigerant, and an evaporation circuit of CO2
refrigerant;
a transfer circuit in which a transfer refrigerant
circulates between a condensation heat exchanger to absorb
heat from the CO2 refrigerant of the evaporation circuit,
and an evaporation heat exchanger to release heat to the CO2
refrigerant of the supracompression circuit;
the supracompression circuit comprising a
compression stage in which CO2 refrigerant having absorbed
heat in the evaporation heat exchanger is compressed to at
least a supracompression state, a cooling stage in which the
CO2 refrigerant from the compression stage releases heat,
and a pressure-regulating unit in a line extending from the
cooling stage to the evaporation heat exchanger to maintain
a pressure differential therebetween;
the evaporation circuit receiving CO2 refrigerant
having released heat in the condensation heat exchanger, the
evaporation circuit comprising a condensation reservoir in
which CO2 refrigerant is accumulated in a liquid state, and
an evaporation stage in which the CO2 refrigerant from the
condensation reservoir absorbs heat to cool an ice-playing
surface, to then return to one of the condensation reservoir
and the condensation exchanger.
2. The CO2 refrigeration system according to claim 1,
wherein the evaporation stage of the evaporation circuit
comprises a heat exchanger being connected to an ice-playing
surface refrigeration circuit in which cycles a second
refrigerant, such that the CO2 refrigerant absorbs heat from
the second refrigerant in the heat exchanger.
3. The CO2 refrigeration system according to claim 1,
wherein the evaporation stage of the evaporation circuit

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comprises pipes under the ice-playing surface in which
circulates the CO2 refrigerant to refrigerate the ice-
playing surface.
4. The CO2 refrigeration system according to claim 3,
further comprising at least one pump in the evaporation
circuit to induce a flow of the CO2 refrigerant in a liquid
state in the pipes under the ice-playing surface.
5. The CO2 refrigeration system according to claim 1,
wherein the cooling stage comprises at least one of a gas-
cooling unit, a heat-reclaim exchanger, and a geothermal gas
cooling unit.
6. The CO2 refrigeration system according to any one
of claims 1 to 5, wherein the condensation heat exchanger is
positioned in a line extending from the condensation
reservoir to the evaporation stage.
7. The CO2 refrigeration system according to any one
of claims 1 to 5, wherein a line extends from a top of the
condensation reservoir to the condensation heat exchanger to
feed gaseous CO2 refrigerant to the condensation heat
exchanger.
8. The CO2 refrigeration system according to any one
of claims 1 to 5, wherein the condensation heat exchanger is
a coil in the condensation reservoir.
9. The CO2 refrigeration system according to any one
of claims 1 to 8, wherein the CO2 refrigerant in the supra-
compression circuit is compressed to a transcritical state.

Description

CA 02766361 2012-01-30
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CO2 REFRIGERATION SYSTEM FOR ICE-PLAYING SURFACE
FIELD OF THE APPLICATION
The present application relates to refrigeration
systems used to refrigerate ice-playing surfaces such as a
skating rinks, curling sheets, etc, and more particularly to
refrigeration systems using CO2 refrigerant.
BACKGROUND OF THE ART
With the growing concern for global warming, the
use of chlorofluorocarbons (CFCs) and hydrochlorofluoro-
carbons (HCFCs) as refrigerant has been identified as having
a negative impact on the environment. These chemicals have
non-negligible ozone-depletion potential and/or global-
warming potential.
As alternatives to CFCs and HCFCs, ammonia, hydro-
carbons and CO2 are used as refrigerants. Although ammonia
and hydrocarbons have negligible ozone-depletion potential
and global-warming potential as does CO2, these refrigerants
are highly flammable and therefore represent a risk to local
safety.
On the other hand, CO2 is environmentally benign
and locally safe.
SUMMARY OF THE APPLICATION
It is therefore an aim of the present disclosure
to provide a CO2 refrigeration system for ice-playing
surfaces that addresses issues associated with the prior
art.
Therefore, in accordance with the present
application, there is provided a CO2 refrigeration system
comprising a transfer circuit for heat exchange between a
supracompression circuit of CO2 refrigerant, and an
evaporation circuit of CO2 refrigerant; a transfer circuit
in which a transfer refrigerant circulates between a
condensation heat exchanger to absorb heat from the CO2
refrigerant of the evaporation circuit, and an evaporation

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heat exchanger to release heat to the CO2 refrigerant of the
supracompression circuit; the supracompression circuit
comprising a compression stage in which CO2 refrigerant
having absorbed heat in the evaporation heat exchanger is
compressed to at least a supracompression state, a cooling
stage in which the CO2 refrigerant from the compression
stage releases heat, and a pressure-regulating unit in a
line extending from the cooling stage to the evaporation
heat exchanger to maintain a pressure differential
therebetween; the evaporation circuit receiving CO2
refrigerant having released heat in the condensation heat
exchanger, the evaporation circuit comprising a condensation
reservoir in which CO2 refrigerant is accumulated in a
liquid state, and an evaporation stage in which the CO2
refrigerant from the condensation reservoir absorbs heat to
cool an ice-playing surface, to then return to one of the
condensation reservoir and the condensation exchanger.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a block diagram of a CO2 refrigeration
system for ice-playing surface in accordance with an
embodiment of the present application, with CO2 refrigerant
in a circuit under the ice-playing surface; and
Fig. 2 is a block diagram of a CO2 refrigeration
system for ice-playing surface in accordance with an
embodiment of the present application, with CO2 refrigerant
cooling brine of a circuit under the ice-playing surface.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to the drawings and more particularly to
Fig. 1, there is illustrated a CO2 refrigeration system 1
for ice-playing surface, while Fig. 2 illustrates a CO2
refrigeration system 2 for ice-playing surface similar to
that of Fig. 1, whereby like reference numerals will refer
to like elements.

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=
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In Fig. 1, the CO2 refrigeration system 1 has a CO2
evaporation circuit 10.
The CO2 evaporation circuit 10
comprises a condensation reservoir 12 accumulating CO2
refrigerant in a liquid and gaseous state.
The CO2
evaporation circuit 10 is in a heat-exchange relation with a
condensation circuit that absorbs heat from the CO2
refrigerant.
Line 14 directs CO2 refrigerant from the
condensation reservoir 12 to an evaporation stage, with a
flow of CO2 refrigerant induced by pump and/or an expansion
valve(s) as generally indicated as 15.
As is shown in
Fig. 1, the CO2 refrigerant is then fed to the ice-playing
surface evaporation stage 17.
The ice-playing surface evaporation stage 17 of
= 15 Fig. 1 consists of a circuit of pipes positioned under the
ice-playing surface, in which the CO2 refrigerant circulates
to absorb heat from fluid being frozen to form the ice-
playing surface, or to maintain the ice-playing surface
frozen.
CO2 refrigerant exiting the evaporation stage 17
is directed to the condensation reservoir 12, by way of
line 18.
The CO2 evaporation circuit 10 is in a heat-
exchange relation with a transfer circuit 20. The transfer
circuit 20 is for instance of the type in which a transfer
refrigerant (e.gõ alcohol-based such as glycol, water,
brine or the like) cycles. A condensation heat exchanger 21
is in fluid communication with the condensation reservoir
12, so as to receive CO2 refrigerant in a gaseous state,
whereby the transfer refrigerant absorbs heat from the CO2
refrigerant in the heat exchanger 21.
According to an
embodiment, the condensation heat exchanger 21 has a coil
that is positioned inside the condensation reservoir 12.
The condensation heat exchanger 21 may also
receive CO2 refrigerant directly from line 14, or from line
18. The transfer circuit 20 is a closed circuit featuring
lines 22 and 23 as well as pump 24 to cycle the transfer

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refrigerant between the heat exchanger 21 and an evaporation
heat exchanger 31 of a supra-compression circuit 30.
Accordingly, the transfer refrigerant absorbs heat from the
CO2 refrigerant circulating in the CO2 evaporation circuit
10, and releases the heat to the CO2 refrigerant circulating
in the supra-compression circuit 30.
In the transfer circuit 20, the condensation
refrigerant circulates between the heat exchanger 21 in
which the transfer refrigerant absorbs heat, and the heat
exchanger 31 in which the transfer refrigerant absorbs heat.
The supra-compression circuit 30
(i.e.,
transcritical circuit if operated at transcritical
pressures) is provided to compress CO2 refrigerant to a
transcritical state, for heating purposes, or supra-
compressed state.
The heat exchanger 31 vaporizes the CO2
refrigerant fed to a supra-compression stage 32. The supra-
compression stage 32 features one or more compressors (e.g.,
BockTM, DorinTm) , that compress the CO2 refrigerant to a
supra-compressed or transcritical state.
Upon exiting the supra-compression stage 32, the
CO2 refrigerant must be cooled by a cooling stage,
embodiments of which are defined herein.
In the supra-compressed or transcritical state,
the CO2 refrigerant is used to heat a secondary refrigerant
via heat-reclaim exchanger 34, via line 33. In the heat-
reclaim exchanger 34, the CO2 refrigerant is in a heat-
exchange relation with a secondary refrigerant circulating
in the secondary refrigerant circuit 35. Alternatively, the
heat-reclaim exchanger 34 may be part of a coil of a
convection heating unit, etc. In an embodiment, the heat-
reclaim exchanger 34, whether directly or via the secondary
circuit, is used to heat the water used in the ice-playing
surface complex (for meeting the hot water demand for
showers, etc), for heating the surroundings of the ice-
playing surface, or for melting zamboni residue in the ice
dump, among other possibilities.

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The secondary refrigerant is preferably an
environmentally-sound refrigerant, such as water or glycol
(although other refrigerants could be used as well), that is
used as a heat-transfer fluid.
Because of the supra-
compressed or transcritical state of the CO2 refrigerant,
the secondary refrigerant circulating in the circuit 35
reaches a high temperature. Accordingly, due to the high
temperature of the secondary refrigerant, lines of smaller
diameter may be used for the secondary refrigerant circuit
35. It
is pointed out that the secondary refrigerant
circuit 35 may be the largest of the circuits of the
refrigeration system 1 in terms of quantity of refrigerant.
Therefore, the compression of the CO2 refrigerant into a
transcritical state by the transcritical circuit allows the
lines of the secondary refrigerant circuit 35 to be reduced
in terms of diameter.
A gas cooling stage 36 is provided in the
transcritical circuit.
The gas cooling stage 36 absorbs
excess heat from the CO2 refrigerant in the transcritical
state, in view of directing the CO2 refrigerant to the heat
exchanger 31.
Although it is illustrated in a parallel
relation with the heat-reclaim exchanger 34, the gas cooling
stage 36 may be in series therewith, or in any other
suitable arrangement.
Moreover, a geothermal gas cooling stage 37 may be
provided, to use the geothermal cool to absorb heat.
Although not shown, appropriate valves are
provided so as to control the amount of CO2 refrigerant
directed to the gas cooling stage 36, in view of the heat
demand from the heat-reclaim exchanger 34.
Moreover, a
bypass line may be provided to bypass the heat-reclaim
exchanger 34, the gas cooling stage 36 and the geothermal
gas cooling 37.
A CO2 pressure-regulating valve 39 is provided to
maintain appropriate pressures at the stages 34 and 36, and
in the heat exchanger 31. The CO2 transcritical pressure-
regulating valve 39 is for instance a DanfossTM valve. Any

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other suitable pressure-control device may be used as an
alternative to the valve 39, such as any type of valve or
loop.
It is considered to operate the supra-compression
circuit (i.e., supra compression 32) with higher operating
pressure.
CO2 refrigerant has a suitable efficiency at a
higher pressure.
More specifically, more heat can be
extracted when the pressure is higher.
Referring to Fig. 2, the CO2 refrigeration system
2 is similar to the CO2 refrigeration system 1, but
comprises an evaporation exchanger 16, by which the CO2
refrigerant of the evaporation circuit 10 absorbs heat from
a closed circuit of pipes of the ice-playing surface
refrigeration stage 17.
An alternative refrigerant
circulates in the closed circuit of pipes of the ice-playing
surface refrigeration stage 17, such as brine, glycol, or
the like.
Although not fully illustrated, numerous valves
are provided to control the operation of the CO2
refrigeration system 1 as described above.
Moreover, a
controller ensures that the various stages of the
refrigeration system 1 operate as described, for instance by
having a plurality of sensors places throughout the
refrigeration system 1.
Numerous other components may be
added to the refrigeration systems 1 and 2 (e.g., valves,
tanks, pumps, compressors, pressure-relief systems, etc.),
to support the configurations illustrated in Figs. 1 and 2.
It is within the ambit of the present invention to
cover any obvious modifications of the embodiments described
herein, provided such modifications fall within the scope of
the appended claims.

Representative Drawing