Cascade refrigeration system with modular ammonia chiller units

Patent metadata

Field	Value
Publication number	US-9664424-B2
Application number	US-201213706122-A
Country	US
Kind code	B2
Filing date	Dec 5, 2012
Priority date	Nov 17, 2010
Publication date	May 30, 2017
Grant date	May 30, 2017

Abstract

A cascade refrigeration system including an upper portion having at least one modular chiller unit that provides cooling to at least one of a low temperature subsystem having a plurality of low temperature loads, and a medium temperature subsystem having a plurality of medium temperature loads. The modular chiller unit includes a refrigerant circuit having at least a compressor, a condenser, an expansion device, and an evaporator. An ammonia refrigerant which may have entrained oil from the compressor circulates within the refrigerant circuit. An oil recycling circuit removes some oil from the ammonia refrigerant for return to the compressor. An oil pot collects oil accumulated in the evaporator and an oil return line drains oil from the oil pot to an ammonia accumulator or directly to the compressor.

First claim

What is claimed is:

1. A cascade refrigeration system, comprising:
a primary portion having at least one modular chiller unit, the primary portion being configured to provides cooling to at least one of a low temperature subsystem having a plurality of low temperature loads, and a medium temperature subsystem having a plurality of medium temperature loads;
the modular chiller unit comprising:
a refrigerant circuit having at least a compressor, a condenser, an expansion device, and an evaporator;
an ammonia refrigerant configured for circulation within the refrigerant circuit;
an ammonia refrigerant accumulator configured to transmit the ammonia refrigerant to the evaporator, to separately receive the ammonia refrigerant from the evaporator, and to receive the ammonia refrigerant from the condenser separate from the ammonia refrigerant received from the evaporator; and
an oil management system downstream of the compressor and configured to remove oil from the ammonia refrigerant, the oil management system having an oil separator disposed between the compressor and the condenser, the oil separator configured to provide oil to an oil reservoir separate from the ammonia refrigerant accumulator, the oil reservoir coupled to the compressor via a pressure regulator, and an oil return line coupled to the evaporator and the ammonia refrigerant accumulator, the oil return line configured to receive oil returned from the evaporator and to provide the oil returned from the evaporator to the accumulator;
wherein the pressure regulator is configured to provide oil to the compressor from the oil reservoir to maintain a target pressure in the oil reservoir.

2. The cascade refrigeration system of claim 1 , further comprising both the low temperature subsystem and the medium temperature subsystem, and wherein the low temperature subsystem comprises a CO2 refrigerant, and the medium temperature subsystem comprises a chilled liquid coolant comprising at least one of water and glycol, so that the cascade refrigeration system comprises only naturally-occurring refrigerants and environmentally safe coolants and is substantially HFC-free.

3. The cascade refrigeration system of claim 1 , further comprising both the low temperature subsystem and the medium temperature subsystem, and wherein the low temperature subsystem comprises a CO2 refrigerant, and the medium temperature subsystem comprises a CO2 liquid coolant, so that the cascade refrigeration system comprises only naturally-occurring refrigerants and coolants and is substantially HFC-free.

4. The cascade refrigeration system of claim 1 , wherein the compressor includes an oil, and a portion of the oil is entrained in the ammonia refrigerant, and wherein the accumulator is configured to receive the oil returned from the evaporator via the oil return line, and to direct the returned oil to the compressor.

5. The cascade refrigeration system of claim 4 , wherein the oil comprises a PAO oil.

6. The cascade refrigeration system of claim 1 , wherein the modular chiller unit contains a critical charge amount of the ammonia refrigerant and operates without an ammonia receiver tank.

7. The cascade refrigeration system of claim 1 , further comprising a control device configured to start and stop the compressor, and to direct oil accumulated in the evaporator to return to the accumulator via the oil return line when the compressor is stopped.

8. The cascade refrigeration system of claim 4 , wherein the oil return line is configured to route oil to the accumulator by gravity.

9. The cascade refrigeration system of claim 4 , wherein the oil return line further comprises an oil pot configured to receive oil from the evaporator, the oil pot operably communicating with a heat source configured to vaporize ammonia entrained within the oil.

10. The cascade refrigeration system of claim 9 , the oil return line further comprising an oil return valve having an open position and a closed position, and the compressor having an on position and an off position, wherein the oil return valve is configured to open when the compressor is in the off position to route oil from the oil pot to the accumulator.

11. The cascade refrigeration system of claim 1 , further comprising an oil recycling circuit including an oil filter, the oil pressure regulator, and the oil reservoir;
wherein the oil separator is configured to separate the oil from the ammonia refrigerant; and
wherein the oil recycling circuit is configured to route the oil from the oil separator through the oil filter, through the oil pressure regulator, and into the oil reservoir.

12. The cascade refrigeration system of claim 1 , wherein the modular chiller unit comprises a plurality of modular chiller units arranged in a parallel configuration and packaged within a transportable enclosure configured for shipping and direct installation at a facility.

13. The cascade refrigeration system of claim 1 , wherein the evaporator and condenser comprise plate heat exchangers formed at least partially from stainless steel.

14. The cascade refrigeration system of claim 1 , wherein the condenser of the modular chiller unit comprises a water-cooled condenser that interfaces with a water coolant loop having one or more heat reclaim devices.

15. The cascade refrigeration system of claim 1 , wherein the condenser of the modular chiller unit comprises an air-cooled microchannel condenser.

16. The cascade refrigeration system of claim 15 , wherein the air-cooled microchannel condenser includes evaporative cooling.

Assignees

• Hill Phoenix Inc
• Phillips Allen

Inventors

• Hinde David K
• Bittner John D
• Zha Shitong
• Wilkerson Jr Joe T

Classifications

• F25B31/004

  oil recirculating arrangements · CPC title

• F25B43/02 Primary

  for separating lubricants from the refrigerant · CPC title

• F25B2600/21

  Refrigerant outlet evaporator temperature · CPC title

• F25B7/00 Primary

  Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit (F25B9/00 takes precedence) · CPC title

• F25B25/005

  using primary and secondary systems · CPC title