Patent Publication Number: US-2013233009-A1

Title: Co2 refrigeration system for ice-playing surface

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority on Canadian Patent Application No. 2,771,113 filed on Mar. 8, 2012, incorporated herewith by reference. 
     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 CO 2  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 CO 2  are used as refrigerants. Although ammonia and hydrocarbons have negligible ozone-depletion potential and global-warming potential as does CO 2 , these refrigerants are highly flammable and therefore represent a risk to local safety. On the other hand, CO 2  is environmentally benign and locally safe. 
     However, CO 2  refrigerant must be compressed to high pressures (e.g., supra-compressed or transcritically compressed) to optimize the efficiency of CO 2  refrigeration systems. Accordingly, existing CO 2  refrigeration systems require numerous components, and this may have an impact on the cost efficiency of such systems. It is therefore desirable to simplify CO 2  refrigeration systems. 
     SUMMARY OF THE APPLICATION 
     It is therefore an aim of the present disclosure to provide a CO 2  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 CO 2  refrigeration system comprising: a CO 2  circuit comprising a compression stage in which CO 2  refrigerant is compressed to at least a supracompression state, a cooling stage in which the CO 2  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 CO 2  refrigerant in the heat exchanger. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram of a CO 2  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 CO 2  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 CO 2  refrigeration system in accordance with an embodiment of the present disclosure. The CO 2  refrigeration system is of the type used to cool ice-playing surfaces, such as the skating rinks, curling sheets, etc. The CO 2  refrigeration system of  FIG. 1  comprises two different circuits in a heat exchange relation. 
     One of the circuits is CO 2  circuit  10 . The CO 2  circuit  10  comprises a supra-compression stage  12 . The supra-compression stage  12  comprises one or more compressors that compress CO 2  refrigerant in a gaseous state to a supra-compressed state. In an embodiment, the CO 2  refrigerant is compressed to a transcritical state. 
     While in the supra-compressed or transcritical state, the CO 2  refrigerant is fed to a gas cooling stage  14 . In the gas cooling stage  14 , the CO 2  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 CO 2  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 CO 2  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 CO 2  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 CO 2  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 CO 2  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 CO 2  in the circuit  10  upstream thereof. Therefore, the CO 2  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 CO 2  refrigerant is fed at a lowered pressure to the side of the heat exchanger  18  in the CO 2  circuit  10 . The CO 2  refrigerant is then directed to the supra compression stage  12 , to complete a refrigeration cycle in the circuit  10 . 
     The CO 2  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 CO 2  refrigerant and the ice-playing surface refrigerant are solely in a heat exchange 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 CO 2  refrigerant of the CO 2  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 CO 2  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 CO 2  refrigerant reaching the compressors of the supra-compression stage  12  is in a gaseous state. 
     It is observed that the CO 2  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 CO 2  refrigeration system is shown with additional components. The CO 2  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 CO 2  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 CO 2  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.