Abstract:
A modular refrigeration system includes a refrigeration loop having a compressor, a condenser, an expansion assembly, and a chiller interconnected by a first piping loop cycling hydrocarbon refrigerant. A high side cooling loop includes a first heat exchanger and a first pump interconnected with the condenser by a second piping loop cycling a cooling fluid, the cooling fluid exchanges heat with the hydrocarbon refrigerant at the condenser. A low side cooling loop includes a second heat exchanger and a second pump interconnected with the chiller by a third piping loop cycling a chilled fluid, the chilled fluid exchanges heat with the hydrocarbon refrigerant at the chiller. A space supports the second heat exchanger and is configured to be maintained within a predetermined temperature range, wherein the total charge of hydrocarbon refrigerant associated with the space does not exceed 150 grams.

Description:
BACKGROUND 
     The present invention relates to refrigeration systems and, more specifically, to a modular refrigeration system utilizing a low charge hydrocarbon refrigerant. 
     A refrigerated merchandiser is generally known in the art. A refrigerated merchandiser is used by grocers, convenience stores, or other sellers of food items to store and display food items within a predetermined temperature range. Refrigerated merchandisers may employ different refrigerants to maintain the predetermined temperature range. Examples of refrigerants may include, but are not limited to, hydrofluorocarbons (HFC), perfluorocarbons (PFC), HFC blends (including R-404A and R-407A), ammonia, carbon dioxide, and hydrocarbons. 
     Unlike inert refrigerants, hydrocarbon refrigerants have additional government regulations due to flammability and/or toxicity. Typically, regulations focus on limiting the quantity of hydrocarbon refrigerant in a single refrigeration circuit. For example, propane is an approved hydrocarbon for use as a refrigerant in certain applications, including commercial refrigerated merchandisers. However, the Environmental Protection Agency (EPA) regulates the amount of propane which may be used to charge a single refrigeration circuit. For example, the EPA typically limits the refrigerant charge in a refrigeration circuit to 150 grams or less of propane refrigerant. This is for safety purposes in order to limit the potential for a dangerous ignition should the propane refrigerant leak from the refrigeration circuit. 
     In order to meet commercial refrigeration demands while also complying with hydrocarbon charge regulations, a single commercially available refrigerated merchandiser will typically employ a plurality of refrigeration circuits that operate in parallel. Each refrigeration circuit will have a refrigeration charge of no more than 150 grams of hydrocarbon refrigerant. The refrigeration circuits cooperatively operate to provide a desired amount of refrigeration. 
     However, refrigerated merchandisers employing a plurality of refrigeration circuits have certain undesirable characteristics. For example, additional components are necessary to operate each of the separate refrigeration circuits. The additional components may include, but are not limited to, additional piping, compressors, condensers, and control technology to achieve a desired amount of refrigeration in the merchandiser. These additional components not only increase initial costs of constructing refrigerated merchandiser systems, but typically lead to higher maintenance costs to maintain the additional components over the life of the systems. Also, the parallel refrigeration circuits in commercially available merchandisers do not maximize cooling load. Instead, the total amount of hydrocarbon refrigerant associated with the merchandiser is increased. So while each refrigeration circuit complies with government regulations, the total amount of hydrocarbon refrigerant associated with the merchandiser exceeds 150 grams, and typically is between 150 and 600 grams. 
     SUMMARY OF THE INVENTION 
     The invention provides, in one aspect, a modular refrigeration system. The system includes a refrigeration loop having a compressor, a condenser, an expansion assembly, and a chiller interconnected by a first piping loop, the first piping loop cycles hydrocarbon refrigerant. A high side cooling loop includes a first heat exchanger and a first pump interconnected with the condenser by a second piping loop, the second piping loop cycles a cooling fluid, the cooling fluid exchanges heat with the hydrocarbon refrigerant at the condenser. A low side cooling loop includes a second heat exchanger and a second pump interconnected with the chiller by a third piping loop, the third piping loop cycles a chilled fluid, the chilled fluid exchanges heat with the hydrocarbon refrigerant at the chiller. A space supports the second heat exchanger and is configured to be maintained within a predetermined temperature range, wherein the total charge of hydrocarbon refrigerant associated with the space does not exceed 150 grams. 
     The invention provides, in another aspect, a refrigeration system. The system includes a refrigeration loop having a compressor, a first heat exchanger, and an expansion assembly, and a second heat exchanger interconnected by a first piping loop, the first piping loop circulating a hydrocarbon refrigerant. A cooling loop circulates a cooling fluid in heat exchange relationship with the hydrocarbon refrigerant within the second heat exchanger, the cooling loop including a pump interconnected with the second heat exchanger and a third heat exchanger by a second piping loop, wherein the third heat exchanger is in heat exchange relationship with an airflow passing through the third heat exchanger, and wherein the airflow is in communication with a space adapted to support product to be cooled. 
     The invention provides, in another aspect, a merchandiser having a case defining a product support area and a refrigeration loop. The refrigeration loop includes a compressor, a heat exchanger, an expansion assembly, and an evaporator fluidly interconnected with each other, the evaporator being disposed in the case, and the refrigeration loop circulating a hydrocarbon refrigerant in heat exchange relationship with an airflow within the case to condition the product support area, wherein the evaporator includes a single, continuous coil through which the hydrocarbon refrigerant is circulated. 
     Other features and aspects of the invention will become apparent by consideration of the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary refrigerated merchandiser embodying the invention. 
         FIG. 2  is a schematic view of an exemplary multi-stage modular refrigeration system embodying the invention. 
         FIG. 3  is a schematic view of another exemplary multi-stage modular refrigeration system similar to the system of  FIG. 2 , wherein the low side includes a fluid loop and the high side includes an air-cooled condenser. 
         FIG. 4  is a schematic view of another exemplary multi-stage modular refrigeration system similar to the system of  FIG. 2 , wherein the low side includes an evaporator and the high side includes a fluid loop. 
     
    
    
     Before any embodiments of the present invention are explained in detail, it should be understood that the invention is not limited in its application to the details or construction and the arrangement of components as set forth in the following description or as illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. It should be understood that the description of specific embodiments is not intended to limit the disclosure from covering all modifications, equivalents and alternatives falling within the spirit and scope of the disclosure. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. 
     DETAILED DESCRIPTION 
     The invention illustrated in the Figures and disclosed herein is generally directed to a multi-stage modular refrigeration system  100 ,  200 ,  300  for a merchandiser  10 . The system  100 ,  200 ,  300  includes a charge of hydrocarbon refrigerant (e.g., propane) not only within regulatory requirements, the system  100 ,  200 ,  300  also includes a single refrigerant loop charged with hydrocarbon refrigerant. For example, the refrigerant charge of the total system does not exceed 150 grams of hydrocarbon refrigerant. Thus, the merchandiser  10  will have a reduced total amount of hydrocarbon refrigerant over known merchandisers. By implementing the multi-stage system disclosed herein, a larger cooling load is placed upon the hydrocarbon refrigerant to provide fewer refrigeration circuits relative to known merchandisers. Eliminating additional refrigeration circuits in turn eliminates additional components, including, but not limited to, piping, compressor(s), condenser(s), and/or control technology to operate a plurality of parallel refrigeration circuits. 
       FIG. 1  illustrates an exemplary refrigerated merchandiser  10  including a case  15  that has a base  20  and opposing sidewalls  25 . The case  15  also includes a top or canopy  30  and a rear wall  35  positioned opposite an access opening  40 . Although the illustrated merchandiser  10  includes a plurality of doors  45  covering the access opening  40 , the merchandiser  10  can be an open-front merchandiser without doors. The doors  45  are mounted to a frame  50  that includes mullions  55  separating each of the doors  45 . Doors  45  may be hinged or sliding doors. The case  15  defines a product support area  60  and has shelves  65  coupled to the rear wall  35  to support product in the product support area  60 . The merchandiser  10  is illustrated as a singular case with one section and one product support area  60  defined by the section. As will be appreciated, the merchandiser can include one or more sections, with each section defining a product support area that makes up the overall product support area  60  of the merchandiser  10 . 
     Although the merchandiser  10  is illustrated as a vertical merchandiser, the merchandiser  10  can take other forms (e.g., a horizontally-oriented merchandiser), or another type of structure (e.g., a storage room) including a conditioned product support area. Also, the merchandiser  10  can be a low temperature merchandiser supporting product conditioned to temperatures less than approximately 32 degrees Fahrenheit, or a medium temperature merchandiser that conditions product to temperatures generally within a temperature range of approximately 32 degrees Fahrenheit to approximately 41 degrees Fahrenheit. Further, merchandiser  10  may be configured to maintain any desired temperature or range of temperatures in product support area  60 . In addition, merchandiser  10  may be an open air merchandiser, a reach-in refrigerator, a floral merchandiser, a wine merchandiser, a dual service merchandiser, or any other known or future developed refrigerated merchandiser for use with the multi-stage modular refrigeration system  100 ,  200 ,  300  that is described in detail below. 
       FIGS. 2-4  illustrate exemplary multi-stage modular refrigeration systems  100 ,  200 ,  300  for providing refrigeration to the merchandiser  10 . Referring to  FIG. 2 , the multi-stage modular refrigeration system  100  includes circuits or fluid loops  110 ,  120 ,  130  arranged in heat transfer relationship to provide refrigeration to the merchandiser  10 . The illustrated refrigeration loop  110  circulates a hydrocarbon refrigerant (e.g., propane) and is defined as a vapor-compression refrigeration loop (referred to as the “refrigeration loop  110 ” for purposes of description only). More specifically, the refrigeration loop  110  includes a compressor  112 , a condenser  116 , an expansion assembly  118 , and a chiller  119 . The compressor  112  is in fluid connection with the condenser  116  via piping  114 , which also fluidly connects the condenser  116  to the expansion assembly  118 , the expansion assembly  118  to the chiller  119 , and the chiller  119  to the compressor  112  to form the refrigeration loop  110 . 
     The compressor  112  may be any suitable mechanical assembly for increasing the pressure of the hydrocarbon refrigerant within refrigeration loop  110 . The condenser  116  may be any suitable heat exchanging assembly for condensing hydrocarbon refrigerant from a gaseous state to a liquid state, and transferring heat away from the hydrocarbon refrigerant. The expansion assembly  118  may be any suitable flow-restricting or metering assembly causing a reduction in pressure of the hydrocarbon refrigerant, including, but not limited to, an expansion valve that may be either internally equalized or externally equalized. The chiller  119  may be any suitable heat exchanging assembly for transferring heat from a chilled fluid to the hydrocarbon refrigerant. 
     The refrigeration loop  110  may be hermetically sealed to avoid discharge or loss of the hydrocarbon refrigerant. The refrigeration loop  110  provides for cycling or circulation of hydrocarbon refrigerant within the loop from the compressor  112  to the condenser  116 , through the expansion assembly  118  to the chiller  119 , and return to the compressor  112 . Preferably, the refrigeration loop  110  will have a refrigeration charge of hydrocarbon refrigerant that does not exceed government limits for such refrigerants, and is within regulatory requirements. For example, the refrigeration loop  110  has a refrigerant charge limit of no more than 150 grams of hydrocarbon refrigerant such as propane. It should be appreciated that the term “hydrocarbon refrigerant” used herein may include other classifications of flammable or toxic refrigerants, including A2L rated refrigerants. Other refrigerants may have alternative refrigerant charge limit regulations. For example, an A2L rated refrigerant has a charge limit of 500 grams. 
     With continued reference to  FIG. 2 , the refrigeration system  100  also includes a second circuit or fluid loop or low side loop  120  (referred to as the “low side loop  120 ” for purposes of description only). The low side loop  120  may be a low side chilled fluid loop that provides a chilled fluid to refrigerate or otherwise maintain a desired temperature of the merchandiser  10 . The chilled fluid can include hydrofluoroether (HFE), or another chilled fluid suitable for providing refrigeration to the merchandiser  10 . 
     The low side loop  120  includes the chiller  119 , a pump  122 , and a heat exchanger  126 . The pump  122  is in fluid communication with the chiller  119  via loop piping  124 . The piping  124  also fluidly connects the chiller  119  to the heat exchanger  126 , and the heat exchanger  126  to the chiller  119  to form the loop  120 . As illustrated, the heat exchanger  126  defines an evaporator of the merchandiser  10  that conditions the product support area  60  via heat exchange with air that flows through the evaporator prior to being discharged into the product support area  60 . The piping  124  may be any suitable material or arrangement to provide a fluid connection within the loop  120  between the chiller  119 , the pump  122 , and the heat exchanger  126 . 
     The low side loop  120  cycles or circulates the chilled liquid in heat exchange relationship with the hydrocarbon refrigerant in the refrigeration loop  110  within the chiller  119 . That is, heat absorbed by fluid circulating within the heat exchanger  126  (due to heat transfer with the air passing through the heat exchanger  126 ) transfers to the hydrocarbon refrigerant circulating within the refrigeration loop  110  to cool the fluid in the loop  120 . 
     With continued reference to  FIG. 2 , the refrigeration system  100  also includes a third circuit or fluid loop or high side loop  130  (referred to as the “high side loop  130 ” for purposes of description only). The high side loop  130  defines a high side cooling fluid loop that circulates a cooling fluid to the condenser  116  to absorb heat from the hydrocarbon refrigerant in the refrigeration loop  110 . The cooling fluid can be water or a mixture of water and ethylene glycol, or another suitable coolant. 
     The high side loop  130  includes the condenser  116 , a pump  132 , and a heat exchanger  136 . The pump  132  is fluidly connected to the condenser  116  by loop piping  134 . The piping  134  also fluidly connects the condenser  116  to the heat exchanger  136 , and the heat exchanger  136  to the condenser  116  to form the high side loop  130 . One or more fans  138  can be provided at the heat exchanger  136  to assist in discharging heat from the cooling fluid. The piping  134  may be any suitable material or arrangement to provide a fluid connection within the loop  130  between the condenser  116 , the pump  132 , and the heat exchanger  136 . The heat exchanger  136  may be any suitable assembly for transferring heat from the cooling fluid in the loop  130 . For example, the heat exchanger  136  may include, but is not limited to, an air-to-fluid or air-to-water heat exchanger. 
     The high side loop  130  is in heat exchange relationship with the refrigeration loop  110  within the condenser  116 . More specifically, heat in the hydrocarbon refrigerant is absorbed by the cooling fluid circulating through the high side loop  130  within the condenser  116  to cool the hydrocarbon refrigerant, which in turn absorbs heat from the low side loop  120  as described above. 
     The components of the refrigeration, low side, and high side loops  110 ,  120 ,  130  may be positioned together at a single location such as at the merchandiser  10 . For example, one or more of the refrigeration, low side, and/or high side loops  110 ,  120 ,  130  may be provided on the canopy  30  and/or within the base  20  of merchandiser  10 . In another example, some or all of the components of the high side loop  130  may be positioned at a remote location from the refrigeration and/or low side loops  110 ,  120 . More specifically, the pump  132 , the heat exchanger  136 , and/or the fans  138  may be provided at a remote location away from the refrigeration and/or the low side loops  110 ,  120 . In addition, the low side and/or the high side loops  120 ,  130  may be assembled as separate modules. The modular assembly will allow for an end user to optionally use existing equipment in place of one or more modules. For example, an end user may omit a module and instead use one or more existing pumps, piping, and/or heat exchangers in the loops  120 ,  130 . 
     In operation of the refrigeration system  100 , hydrocarbon refrigerant is cycled through refrigeration loop  110 . The hydrocarbon refrigerant flows from the chiller  119  to the compressor  112 , which compresses the hydrocarbon refrigerant in a gas phase. The compressor  112  also acts as the circulation device for the hydrocarbon refrigerant within the refrigeration loop  110 . Compressed hydrocarbon refrigerant exits the compressor  112  and travels to the condenser  116 . In the condenser  116 , heat from the gas phase hydrocarbon refrigerant transfers to the cooling fluid circulating through the high side loop  130 . Heat transfer within the condenser  116  condenses the hydrocarbon refrigerant from a gas to a gas-liquid mixture or liquid. The condensed hydrocarbon refrigerant exits the condenser  116  and travels to the expansion assembly  118 , which restricts the flow of hydrocarbon refrigerant traveling to the chiller  119 , causing a drop in pressure. The drop in pressure results in the hydrocarbon refrigerant changing phase to a gas. This direct expansion of the hydrocarbon refrigerant in the chiller  119  cools the fluid circulating through the low side loop  120 . More specifically, the hydrocarbon refrigerant absorbs heat from the fluid in the low side loop  120  within the chiller  119 . The heated hydrocarbon refrigerant exits the chiller  119  and returns to the compressor  112 , where the cycle repeats. 
     As hydrocarbon refrigerant cycles through the refrigeration loop  110 , fluid also cycles through the low side loop  120  and cooling fluid cycles through the high side loop  130 . In the low side loop  120 , the pump  122  acts as the circulation device for the fluid. The fluid exits the pump  122  and travels to the heat exchanger  126 , where the fluid is heated by heat exchange with warmer air flowing through the heat exchanger  126  to cool the air. The heated fluid then flows to the chiller  119 , where the fluid is cooled by heat exchange with the hydrocarbon refrigerant (by direct expansion of the hydrocarbon refrigerant). The chilled fluid exits the chiller  119  and returns to the pump  122 . 
     In the high side loop  130 , the pump  132  acts as the circulation device for the cooling fluid. The cooling fluid exits the pump  132  and travels to the heat exchanger  136 , where the temperature of the cooling fluid decreases due to rejection of heat to the surrounding environment. The lower temperature cooling fluid exits the heat exchanger  136  and flows to the condenser  116 . In the condenser  116 , the cooling fluid is heated via heat exchange with the hydrocarbon refrigerant (i.e. the cooling fluid absorbs heat from the hydrocarbon refrigerant). The higher temperature cooling fluid exits the condenser  116 , and travels to the pump  132 , where the cycle repeats. 
       FIG. 3  illustrates another exemplary multi-stage modular refrigeration system  200 . Except as described below, the multi-stage modular refrigeration system  200  is the same as the refrigeration system  100  described with regard to  FIG. 2 , and common elements are given the same reference numerals. 
     Referring to  FIG. 3 , the refrigeration system  200  includes the refrigeration loop  110  and the low side loop  120 . However, refrigeration system  200  does not include a high side loop, such as loop  130  in  FIG. 2 . Instead, the system  200  includes one or more fans  138  that are positioned in communication with the condenser  116  to direct air through the condenser  116 . The air acts as a medium to cool the propane refrigerant within the condenser without an intermediate cooling fluid as described and illustrated with regard to  FIG. 2 . 
       FIG. 4  illustrates yet another exemplary multi-stage modular refrigeration system  300 . Except as described below, the multi-stage modular refrigeration system  200  is the same as the refrigeration system  100  described with regard to  FIG. 2 , and common elements are given the same reference numerals. 
     The refrigeration system  300  includes the high side loop  130  and a low side refrigeration loop  310 . As illustrated, the refrigeration loop  310  circulates a hydrocarbon refrigerant (e.g., propane) and includes an evaporator  319  that is positioned in the merchandiser  10  to condition the product support area  60  via heat exchange with air flowing through the evaporator  319 . The refrigeration loop  310  may be hermetically sealed to avoid discharge or loss of hydrocarbon refrigerant. The compressor  112  compresses hydrocarbon refrigerant and acts as the circulation device for the loop  310 . Accordingly, refrigerant flows from the compressor  112  to the condenser  116 , and then exits the condenser  116  and travels through the expansion assembly  118  to the evaporator  319  before returning to the compressor  112 . Refrigeration loop  310  has a refrigerant charge that is no more than 150 grams of hydrocarbon refrigerant. 
     In operation of the refrigeration system  300 , hydrocarbon refrigerant is circulated through the refrigeration loop  310  to cool air that is eventually directed to the product support area  60  to condition product supported therein. Heated hydrocarbon refrigerant from the evaporator  319  is compressed by the compressor  112  and then cooled via heat exchange with the cooling fluid in the high side loop  130  within the condenser  116 . 
     By utilizing fluid loops arranged in heat transfer relationship, the refrigeration system  100 ,  200 ,  300  reduces the total hydrocarbon refrigerant needed to refrigerate the product support area  60  by increasing the cooling load on the hydrocarbon refrigerant. Unlike known systems, the series arrangement of fluid loops and use of hydrocarbon refrigerant provides a single hydrocarbon refrigerant loop that maintains the area  60  within the desired parameters. 
     Further, the series arrangement of fluid loops eliminates or at least reduces duplicative refrigeration components (e.g., pumps, compressors, piping, etc.) within the system  100 ,  200 ,  300 . In addition, the modular assembly of multi-stage loops  110 ,  120 ,  130 ,  310  allows an end user to optionally utilize existing equipment in place of one or more modules while still maximizing the use of hydrocarbon refrigerant. For example, an end user may omit a module and instead use one or more existing pumps, piping, and/or heat exchangers in place of the omitted module. 
     Various features and advantages of the invention are set forth in the following claims.