NONFLAMMABLE REFRIGERANTS HAVING LOW GWP, AND SYSTEMS FOR AND METHODS OF PROVIDING REFRIGERATION

1 . A cascade refrigeration system, comprising:

a. a low stage refrigeration circuit comprising:

a low stage refrigerant having a GWP of about 150 or less; and

a compressor;

b. an inter-circuit heat exchanger in which said low stage refrigerant condenses; and

c. a high stage refrigeration circuit comprising a high stage refrigerant which: (i) has either Class A1 or Class A2L flammability; (ii) evaporates at a temperature below said low stage refrigerant condensing temperature; and

(iii) comprises at least about 77% by weight of HFO-1234ze(E), wherein said high stage refrigerant evaporates in said inter-circuit heat exchanger by absorbing heat from said refrigerant in said low stage refrigeration circuit.

2 . The cascade refrigeration system of claim 1 wherein said high stage refrigerant has a Class A1 flammability.

3 . The cascade refrigeration system of claim 1 wherein said high stage refrigerant comprises at least about 75% of HFO-1234ze(E).

4 . The cascade refrigeration system of claim 3 wherein said high stage refrigerant consists essentially of HFO-1234ze(E).

5 . The cascade refrigeration system of claim 4 wherein said low stage refrigerant consists essentially of CO2.

6 . The cascade refrigeration system of claim 3 wherein said high stage refrigerant consists essentially of R471 A.

7 . The cascade refrigeration system of claim 3 wherein said high stage refrigerant consists essentially of R476 A.

8 . The cascade refrigeration system of claim 3 wherein said low stage refrigerant consists essentially of propane.

9 . The cascade refrigeration system of claim 8 wherein said high stage refrigerant consists essentially of R471 A.

10 . The cascade refrigeration system of claim 8 wherein said high stage refrigerant consists essentially of R476 A.

11 . The cascade refrigeration system of claim 3 wherein said low stage refrigerant consists essentially of HFO-1234yf.

12 . The cascade refrigeration system of claim 3 wherein said low stage refrigerant consists essentially of R454C.

13 . The cascade refrigeration system of claim 13 wherein said high stage refrigerant consists essentially of R476 A.

14 . The cascade refrigeration system of claim 3 wherein said low stage refrigerant consists essentially of R455 A.

15 . The cascade refrigeration system of claim 14 herein said high stage refrigerant consists essentially of R471 A.

16 . The cascade refrigeration system of claim 14 wherein said high stage refrigerant consists essentially of R476 A.

17 . The cascade refrigeration system of claim wherein said low stage refrigeration circuit comprises a plurality of low temperature refrigeration circuits.

18 . The cascade refrigeration system of claim 1 wherein said low stage refrigeration circuit compressor comprises at least one compressor having a horsepower rating of about 2 horsepower or less.

19 . A method for proving cooling in an extreme temperature air conditioning system comprising:

a. providing an air conditioning system comprising a compressor, a condenser, an evaporator and a refrigerant, said refrigerant comprising:

i. about 78.7% by weight of HFO-1234ze(E),

ii. about 4.3% by weight of HFC-227ea; and

iii. about 17% by weight of HFO-1336mzz(E);

b. evaporating said refrigerant in said evaporator, and

c. condensing said refrigerant at a temperature in the range of from about from about 55° C. to about 95° C.

20 . A method for proving cooling in a high temperature heat pump comprising:

a. providing a heat pump comprising a compressor, a condenser, an evaporator and a refrigerant, said refrigerant comprising:

i. about 78.7% by weight of HFO-1234ze(E),

ii. about 4.3% by weight of HFC-227ea; and

iii. about 17% by weight of HFO-1336mzz(E);

b. evaporating said refrigerant in said evaporator, and

c. condensing said refrigerant at a temperature in the range of from about from about 55° C. to about 95° C.