CO2 REFRIGERATION SYSTEM FOR ICE-PLAYING SURFACE

SYSTEME DE REFRIGERATION AU CO2 POUR SURFACES DE SPORT SUR GLACE

English Abstract

A CO2 refrigeration system comprises a CO2 circuit. In a compression stage of
the circuit, CO2 refrigerant is compressed to a supracompression state. In a
cooling stage, the
CO2 refrigerant from the compression stage releases heat. A pressure-
regulating unit in a line
extending from the cooling stage to one side of a heat exchanger maintains a
pressure differential.
A second refrigerant cycles in a cooling circuit between a second side of the
heat exchanger and
an ice-playing surface. The second refrigerant absorbs heat from the ice-
playing surface and
releases heat to the CO2 refrigerant in the heat exchanger.

Claims

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CLAIMS:
1. A CO2 refrigeration system comprising :
a CO2 circuit comprising a compression stage in which CO2 refrigerant is
compressed to at least a supracompression state, a cooling stage in which the
CO2 refrigerant
from the compression stage releases heat, a pressure-regulating unit in a line
extending from the
cooling stage to one side of a heat exchanger to maintain a pressure
differential therebetween;
and
a cooling circuit in which cycles a second refrigerant between a second side
of the
heat exchanger and an ice-playing surface, such that the second refrigerant
absorbs heat from the
ice-playing surface and releases heat to the CO2 refrigerant in the heat
exchanger.
2. 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
heating unit.
3. The CO2 refrigeration system according to claim 2, comprising a plurality
of the
heating unit, with valves provided in relation to the plurality of heating
unit to individually control an
amount of CO2 refrigerant directed to each said heating unit.
4. The CO2 refrigeration system according to claim 3, wherein a fan of each
said
heating unit is controlled by a controller as a function of a temperature
demand and of said amount
of CO2 refrigerant.
5. The CO2 refrigeration system according to claim 1, further comprising at
least one
pump in the cooling circuit to induce a flow of the CO2 refrigerant therein.
6. The CO2 refrigeration system according to claim 1, further comprising a CO2
condensation reservoir between the heat exchanger and the compression stage.
7. The CO2 refrigeration system according to claim 1, further comprising a
line
extending directly from the heat exchanger to the compression stage.
8. The CO2 refrigeration system according to any one of claims 1 to 7, wherein
the
heat exchanger is a shell and tube type of heat exchanger, with the CO2
circuit side of the heat
exchanger being the shell, the cooling side of the heat exchanger being the
tubes.

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9. The CO2 refrigeration system according to claim 1, wherein the cooling
circuit
comprises pipes under the ice-playing surface in which circulates the CO2
refrigerant to refrigerate
the ice-playing surface.
10. The CO2 refrigeration system according to any one of claims 1-9, wherein
the CO2
refrigerant in the CO2 circuit is compressed to a transcritical state.

Description

CA 02771113 2012-03-08
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CO2 REFRIGERATION SYSTEM FOR ICE-PLAYING SURFACE
FIELD OF THE APPLICATION
The present application relates to refrigeration systems used for cooling ice-
playing surfaces such as hockey rinks, skating rinks, curling sheets, etc,
and, more particularly, to
such refrigeration systems using CO2 as refrigerant.
BACKGROUND OF THE ART
With the growing concern for global warming, the use of chlorofluorocarbons
(CFCs) and hydrochlorofluorocarbons (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, hydrocarbons and C02 are used
as refrigerants. Although ammonia and hydrocarbons have negligible ozone-
depletion potential
and global-warming potential as does C02i these refrigerants are highly
flammable and therefore
represent a risk to local safety. On the other hand, CO2 is environmentally
benign and locally safe.
1s However, C02 refrigerant must be compressed to high pressures (e.g., supra-
compressed or transcritically compressed) to optimize the efficiency of CO2
refrigeration systems.
Accordingly, existing CO2 refrigeration systems require numerous components,
and this may have
an impact on the cost efficiency of such systems. It is therefore desirable to
simplify C02
refrigeration systems.
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 CO2 circuit comprising a compression stage
in which CO2
refrigerant is compressed to at least a supracompression state, a cooling
stage in which the C02
refrigerant from the compression stage releases heat, a pressure-regulating
unit in a line
extending from the cooling stage to one side of a heat exchanger to maintain a
pressure
differential therebetween; and a cooling circuit in which cycles a second
refrigerant between a
second side of the heat exchanger and an ice-playing surface, such that the
second refrigerant
absorbs heat from the ice-playing surface and releases heat to the C02
refrigerant in the heat
exchanger.

CA 02771113 2012-03-08
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BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a block diagram of a CO2 refrigeration system for an ice-playing
surface
in accordance with an embodiment of the present disclosure; and
Fig. 2 is a block diagram of the CO2 refrigeration system of Fig. 1 with
additional
components.
DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to the drawings and more particularly to Fig. 1, there is
illustrated a CO2
refrigeration system in accordance with an embodiment of the present
disclosure. The CO2
refrigeration system is of the type used to cool ice-playing surfaces, such as
the skating rinks,
curling sheets, etc. The CO2 refrigeration system of Fig. I comprises two
different circuits in a heat
exchange relation.
One of the circuits is CO2 circuit 10. The CO2 circuit 10 comprises a supra-
compression stage 12. The supra-compression stage 12 comprises one or more
compressors
that compress CO2 refrigerant in a gaseous state to a supra-compressed state.
In an
embodiment, the CO2 refrigerant is compressed to a transcritical state.
While in the supra-compressed or transcritical state, the CO2 refrigerant is
fed to a
gas cooling stage 14. In the gas cooling stage 14, the CO2 refrigerant in the
supra-compressed or
transcritical state releases heat. The heat release may be in some form of
heat reclaiming. For
instance, heat is reclaimed from the CO2 refrigerant by heating up water
(e.g., water tank), or by
heating equipment (e.g., ice melting equipment, hot air blowers, etc.). The
gas cooling stage 14
may consists of one or more heat exchangers for the CO2 refrigerant to be in
the heat exchange
relation with a secondary refrigerant (e.g., glycol) to recuperate the heat
and direct it to remotely
located heating equipment. The gas cooling stage 14 may comprises numerous
heat exchange
components to remove heat from the CO2 refrigerant. For instance, the coiling
stage 14 may
comprises a plurality of heating units, with valves provided in relation to
the plurality of heating unit
to individually control an amount of CO2 refrigerant directed to each of the
heating units. The fan
of each heating unit may be controlled by a controller as a function of a
temperature demand and
of the amount of CO2 refrigerant fed to each heating unit.
A pressure regulating unit 16 is positioned in the circuit 10 downstream of
the gas
cooling stage 14, and upstream of a heat exchanger(s) 18. The pressure
regulating unit 16 may
be any valve or arrangement of valves, etc. that will maintain a high pressure
of CO2 in the circuit
10 upstream thereof. Therefore, the CO2 refrigerant is kept in the supra-
compressed or
transcritical state between the supra compression stage 12 and the pressure
regulating unit 16, to
optimize the efficiency of the gas cooling stage 14. Because of the pressure
regulating unit 16, the
CO2 refrigerant is fed at a lowered pressure to the side of the heat exchanger
18 in the CO2 circuit

CA 02771113 2012-03-08
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10. The CO2 refrigerant is then directed to the supra compression stage 12, to
complete a
refrigeration cycle in the circuit 10.
The CO2 refrigerant in the circuit 10 is in a heat exchange relation with
another
refrigerant in a cooling circuit 20, by way of the heat exchanger 18. The
cooling circuit 20 extends
from the second side of the heat exchanger 18 to coils or pipes located under
an ice-playing
surface, or to a heat exchanger that will ultimately absorb heat from the ice-
playing surface. The
refrigerant circulating in the cooling circuit 20 may be brine, water, glycol
or any appropriate
refrigerant that is circulated in the coils of pipes of an ice-playing
surface. In the heat exchanger
18, the CO2 refrigerant and the ice-playing surface refrigerant are solely in
a heat exchange
io relation and, hence, do not mix. In an embodiment, the heat exchanger 18 is
a shell-and-tube type
of heat exchanger. Therefore, the shell of the heat exchanger 18 may act as a
reservoir for CO2
refrigerant of the CO2 circuit 10, with the line relating to heat exchanger 18
to the supra
compression stage 12 being connected to a top of the reservoir of the heat
exchanger 18 for the
suction of gaseous CO2 refrigerant. The tubes would define the second side of
the heat exchanger
18 and thus the second refrigerant would circulate therein. Alternatively, the
network of pipes
relating the heat exchanger 18 to the supra compression stage 12 may act as
reservoir. Additional
components may be provided to ensure that the CO2 refrigerant reaching the
compressors of the
supra-compression stage 12 is in a gaseous state.
It is observed that the CO2 refrigeration system for the ice-playing surface
of Fig. 1
distinguishes by its simplicity and minimum amount of components.
Referring to Fig. 2, an alternative embodiment of this CO2 refrigeration
system is
shown with additional components. The CO2 refrigeration circuit 10 features a
condensation
reservoir 30 that is positioned between the heat exchanger 18 and the supra-
compression stage
12. The condensation reservoir 30 collects CO2 in a generally liquid state. In
an embodiment, the
line connecting the condensation reservoir 30 to the supra compression stage
12 are positioned
atop the condensation reservoir 30 to collect CO2 that is in a generally
gaseous state.
This cooling circuit 20 may feature a pump 32 that will circulate the ice-
playing
surface refrigerant between the heat exchanger 18 and the coils or pipes of
the ice-playing surface
34. The pump 32 may be positioned either upstream or downstream of the heat
exchanger 18.
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