Refrigeration systems and methods

Abstract

Disclosed are cascaded refrigeration systems, comprising: a plurality of refrigeration units, each refrigeration unit containing a first refrigeration circuit, each first refrigeration circuit comprising an evaporator and a heat exchanger; and a second refrigeration circuit; wherein each first circuit heat exchanger is arranged to transfer heat energy between its respective first refrigeration circuit and the second refrigeration circuit.

What is claimed is: 
     
         1 . A cascaded refrigeration system comprising:
 (a) a plurality of low temperature refrigeration circuits, with each low temperature refrigeration circuit comprising:
 (i) a flammable low temperature refrigerant consisting essentially of HFO-1234yf, R-455A, propane and combinations of two or more of these and having a GWP of about 150 or less; 
 (ii) a compressor having a horse power rating of about 2 horse power or less; and 
 (iii) a heat exchanger in which said flammable low temperature refrigerant condenses at a temperature of from about −5° C. to about −15° C. to produce a liquid refrigerant; and 
 (iv) a suction line heat exchanger connected upstream of said compressor for cooling said liquid refrigerant from same condenser by adding heat to the gas entering the compressor; and 
   (b) a medium temperature refrigeration circuit comprising a non-flammable medium temperature refrigerant selected from the group consisting of (i) R515A; (ii) R515B; (iii) a mixture comprising on a weight basis about 70% R1234y and about 30% CF3I (FH); (iv) a mixture comprising on a weight basis about 78% R1234ze, about 2% R1233zd and about 20% CF3I (A1); and (v) a mixture comprising on a weight basis about 84% R1234ze, about 2% R1233zd and about 9.6% CF3I (A2), wherein said refrigerant evaporates at a temperature below said low temperature refrigerant condensing temperature and in the range of about −5° C. to about −15° C., wherein said medium temperature refrigerant evaporates in said heat exchanger by absorbing heat from said flammable refrigerant in said low temperature refrigeration circuit.   
     
     
         2 . The cascaded refrigeration system of  claim 1 , wherein two or more of said low temperature refrigeration circuits are each in a separate modular refrigeration unit and wherein said at least two modular refrigeration units is located in a first area open to the public. 
     
     
         3 . The cascaded refrigeration system of  claim 2 , wherein the second refrigeration circuit includes portions that extend the second refrigeration circuit between the first area and a second area comprising a machine room. 
     
     
         4 . The cascaded refrigeration system of claim  34 , wherein the second refrigeration circuit includes portions that extend the second refrigeration circuit to a third area. 
     
     
         5 . The cascaded refrigeration system of  claim 1 , wherein each first refrigeration circuit further comprises a fluid expansion device and wherein the fluid expansion device is a capillary tube and/or an orifice tube. 
     
     
         6 . The cascaded refrigeration system of  claim 1  wherein said flammable low temperature refrigerant is R-1234yf and said non-flammable medium temperature refrigerant is A1 and/or A2. 
     
     
         7 . The cascaded refrigeration system of  claim 1  wherein said flammable low temperature refrigerant is R-455A and said non-flammable medium temperature refrigerant is A1 and/or A2. 
     
     
         8 . The cascaded refrigeration system of  claim 1  wherein said flammable low temperature refrigerant is R-455A and said non-flammable medium temperature refrigerant is A1 and/or A2. 
     
     
         9 . The cascaded refrigeration system of any of claims  1 - 32  wherein said medium temperature refrigeration system is located substantially completely outside of said low temperature refrigeration. 
     
     
         10 . The cascaded refrigeration system of claim wherein said heat exchanger is a flooded heat exchanger.