Modular CO2 refrigeration system

Patent metadata

Field	Value
Publication number	US-9470435-B2
Application number	US-201314137072-A
Country	US
Kind code	B2
Filing date	Dec 20, 2013
Priority date	Aug 7, 2008
Publication date	Oct 18, 2016
Grant date	Oct 18, 2016

Abstract

A cascade CO2 refrigeration system includes a medium temperature loop for circulating a medium refrigerant and a low temperature loop for circulating a CO2 refrigerant. The medium temperature loop includes a heat exchanger having a first side and a second side. The first side evaporates the medium temperature refrigerant. The low temperature loop includes a discharge header for circulating the CO2 refrigerant through the second side of the heat exchanger to condense the CO2 refrigerant, a liquid-vapor separator collects liquid CO2 refrigerant and directs vapor CO2 refrigerant to the second side of the heat exchanger. A liquid CO2 supply header receives liquid CO2 refrigerant from the liquid-vapor separator. Medium temperature loads receive liquid CO2 refrigerant from the liquid supply header for use as a liquid coolant at a medium temperature. An expansion device expands liquid CO2 refrigerant from the liquid supply header into a low temperature liquid-vapor mixture for use by the low temperature loads.

First claim

What is claimed is:

1. A cascade CO2 refrigeration system, comprising:
a medium temperature loop for circulating a medium temperature refrigerant, the medium temperature loop including a heat exchanger having a first side and a second side, the first side configured to evaporate the medium temperature refrigerant and a medium temperature compressor, a condenser, and a medium temperature expansion device packaged in a modular unit with the heat exchanger;
a low temperature loop for circulating a CO2 refrigerant, the low temperature loop including:
a low temperature discharge header configured to circulate the CO2 refrigerant through the second side of the heat exchanger, the second side of the heat exchanger configured to condense the CO2 refrigerant;
a liquid-vapor separator configured to collect liquid CO2 refrigerant and to direct vapor CO2 refrigerant to the second side of the heat exchanger;
a pump;
a liquid CO2 refrigerant supply header;
a plurality of medium temperature loads configured to receive liquid CO2 refrigerant from the liquid CO2 refrigerant supply header for use as a liquid coolant in the medium temperature loads and to discharge the CO2 refrigerant directly to the liquid-vapor separator;
a plurality of low temperature loads;
a low temperature expansion device associated with the low temperature loads and configured to expand the liquid CO2 refrigerant from the liquid CO2 refrigerant supply header into vapor CO2 refrigerant for use as a vapor refrigerant by the low temperature loads.

2. The cascade CO2 refrigeration system of claim 1 further comprising a return header configured to direct vapor CO2 refrigerant from the medium temperature loads to the liquid-vapor separator.

3. The cascade CO2 refrigeration system of claim 2 wherein the CO2 refrigerant from the medium temperature loads is in a combined liquid-vapor state.

4. The cascade CO2 refrigeration system of claim 1 further comprising a low temperature suction header configured to direct CO2 refrigerant from the low temperature loads to one or more low temperature compressors.

5. The cascade CO2 refrigeration system of claim 4 wherein the CO2 refrigerant from the low temperature loads is vapor CO2 refrigerant.

6. The cascade CO2 refrigeration system of claim 5 wherein the vapor CO2 refrigerant from the low temperature loads is configured to provide cooling to a low temperature subcooler.

7. The cascade CO2 refrigeration system of claim 1 further comprising a plurality of the modular units coupled to the liquid-vapor separator.

8. The cascade CO2 refrigeration system of claim 1 , further comprising an air-cooled heat exchanger disposed upstream of the heat exchanger and configured to use ambient air to pre-cool the CO2 refrigerant.

9. A cascade refrigeration system having a common subcooled liquid supply for both low temperature refrigerated cases and medium temperature refrigerated cases, the system comprising:
an upper cascade portion for circulating a first refrigerant, the upper cascade portion including an upper cascade compressor, an upper cascade condenser, an upper cascade expansion device, and a heat exchanger having a first side and a second side, the first side configured to evaporate the first refrigerant;
a lower cascade portion for circulating a second refrigerant, the lower cascade portion including a lower cascade compressor configured to direct the second refrigerant to the second side of the heat exchanger, the second side of the heat exchanger configured to condense the second refrigerant, a liquid-vapor separator configured to direct liquid second refrigerant to the common subcooled liquid supply and to direct vapor second refrigerant to the second side of the heat exchanger;
a plurality of medium temperature refrigerated cases configured to receive liquid second refrigerant from the common subcooled liquid supply for use as a coolant in the medium temperature refrigerated cases and to discharge the second refrigerant directly to the liquid-vapor separator, and
an expansion device associated with a plurality of the low temperature refrigerated cases and configured to expand the liquid second refrigerant from the common subcooled liquid supply for use in the low temperature refrigerated cases.

10. The cascade refrigeration system of claim 9 wherein the second refrigerant comprises CO2.

11. The cascade refrigeration system of claim 9 wherein the first refrigerant comprises one of propane and ammonia.

12. The cascade refrigeration system of claim 9 further comprising a return header configured to direct second refrigerant in a combined liquid-vapor state from the medium temperature refrigerated cases to the liquid-vapor separator.

13. The cascade refrigeration system of claim 9 further comprising a lower cascade suction header configured to direct second refrigerant from the low temperature refrigerated cases to a lower cascade heat exchanger configured to subcool the liquid second coolant from the liquid-vapor separator.

14. The cascade refrigeration system of claim 9 wherein the upper cascade compressor, the upper cascade condenser, the upper cascade expansion device, and the heat exchanger are packaged in a modular unit.

15. The cascade refrigeration system of claim 14 further comprising a plurality of the modular units coupled to the liquid-vapor separator and configured to condense vapor second refrigerant.

16. The cascade refrigeration system of claim 9 further comprising a de-superheating heat exchanger disposed between the lower cascade compressor and the heat exchanger and configured to pre-cool the second refrigerant before entering the heat exchanger.

17. The cascade refrigeration system of claim 9 further comprising a pump configured to direct the liquid second refrigerant from the liquid-vapor separator to the medium temperature refrigerated cases.

18. A cascade refrigeration system having a common liquid supply for both low temperature refrigeration loads and medium temperature refrigeration loads, the system comprising:
an upper cascade portion for circulating a first refrigerant, the upper cascade portion including an upper cascade compressor, an upper cascade condenser, an upper cascade expansion device, and a heat exchanger having a first side and a second side, the first side configured to evaporate the first refrigerant;
a lower cascade portion for circulating a second refrigerant, the lower cascade portion including a lower cascade compressor configured to direct the second refrigerant to the second side of the heat exchanger, the second side of the heat exchanger configured to condense the second refrigerant;
a liquid-vapor separator configured to receive the liquid second refrigerant from the second side of the heat exchanger and to provide a source of liquid second refrigerant for the common liquid supply;
a plurality of medium temperature refrigeration loads configured to receive liquid second refrigerant from the common liquid supply for use as a coolant in the medium temperature refrigeration loads and to discharge the second refrigerant directly to the liquid-vapor separator, and
an expansion device associated with a plurality of the low temperature refrigeration loads and configured to expand the liquid second refrigerant from the common liquid supply into a liquid-vapor mixture for use in the low temperature refrigeration loads.

19. The cascade refrigeration system of claim 18 wherein the second refrigerant is CO2.

20. The cascade refrigeration system of claim 18 wherein the

Assignees

• Hill Phoenix Inc

Inventors

• Hinde David K
• Zha Shitong
• Lan Lin
• Martin J Scott
• Gallaher John M

Classifications

• F25B2400/23

  Separators · CPC title

• F25B2400/22

  Refrigeration systems for supermarkets · CPC title

• F25B2400/075

  with parallel compressors · CPC title

• F25B2309/06

  Compression machines, plants or systems characterised by the refrigerant being carbon dioxide · CPC title

• F25B43/006

  Accumulators · CPC title