Carbon dioxide refrigerant vapor compression system

Patent metadata

Field	Value
Publication number	US-9951975-B2
Application number	US-86306008-A
Country	US
Kind code	B2
Filing date	Jan 17, 2008
Priority date	Jan 17, 2008
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

A carbon dioxide refrigerant vapor compression system and method of operating that system are provided. The refrigerant vapor compression system includes a compression device, a flash tank receiver disposed in the refrigerant circuit intermediate a refrigerant heat rejection heat exchanger and a refrigerant heat absorption heat exchanger, and a compressor unload circuit including a refrigerant line establishing refrigerant flow communication between an intermediate pressure stage of the compression device and the refrigerant circuit at a location downstream of the refrigerant heat absorption heat exchanger and upstream of a suction inlet to the compression device, and a unload circuit flow control device disposed in said unload circuit refrigerant line. In response to at least one system operating parameter sensed by at least one sensor, the controller selectively positions the unload flow control device to maintain the refrigerant vapor compression system operating below a preselected high pressure limit.

First claim

We claim:

1. A carbon dioxide refrigerant vapor compression system comprising:
a refrigerant circuit including a refrigerant compression device, a refrigerant heat rejection heat exchanger for passing carbon dioxide refrigerant received from said compression device at a first pressure in heat exchange relationship with a cooling medium, a refrigerant heat absorption heat exchanger for passing carbon dioxide refrigerant at a second pressure lower than the first pressure in heat exchange relationship with a heating medium, and an expansion device disposed in the refrigerant circuit downstream of said refrigerant heat rejection heat exchanger and upstream of said refrigerant heat absorption heat exchanger;
a flash tank receiver disposed in the refrigerant circuit downstream of said refrigerant heat rejection heat exchanger and upstream of said expansion device;
a compressor unload circuit including a refrigerant line establishing refrigerant flow communication between an intermediate pressure stage of said compression device and said refrigerant circuit at a location downstream of said refrigerant heat absorption heat exchanger and upstream of a suction inlet to said compression device, and an unload circuit flow control device disposed in said unload circuit refrigerant line; and
a controller operatively associated with said expansion device and said unload circuit flow control device, said controller operative in response to at least one of refrigerant discharge pressure sensed at an outlet of the refrigerant compression device and refrigerant discharge temperature sensed at an outlet of the refrigerant compression device to selectively position the unload circuit flow control device to maintain said refrigerant vapor compression system operating at a discharge pressure below a preselected upper limit, wherein said preselected upper limit is the critical point pressure for carbon dioxide;
an ambient temperature sensor, the controller operative in response to an ambient temperature to selectively control an operating mode of the vapor compression system.

2. A refrigerant vapor compression system as recited in claim 1 wherein said compression device comprises a single reciprocating compressor having at least two compression stages.

3. A refrigerant vapor compression system as recited in claim 1 wherein said compression device comprises at least two reciprocating compressors disposed in the refrigerant circuit in a series relationship with respect to refrigerant flow.

4. A refrigerant vapor compression system as recited in claim 1 wherein the heating medium comprises air circulated through the refrigerant heat absorption heat exchanger from a controlled temperature environment.

5. A refrigerant vapor compression system as recited in claim 1 wherein the heating medium comprises air circulated through the refrigerant heat absorption heat exchanger from a temperature controlled perishable cargo storage zone.

6. A method for controlling operation of a carbon dioxide refrigerant vapor compression system including a refrigerant compression device, a refrigerant heat rejection heat exchanger, a flash tank receiver, an expansion device, and a refrigerant heat absorption heat exchanger disposed in series flow arrangement in the refrigerant circuit, said method comprising:
providing a compressor unload circuit including a refrigerant line establishing refrigerant flow communication between an intermediate pressure stage of said compression device and said refrigerant circuit at a location downstream of said refrigerant heat absorption heat exchanger and upstream of a suction inlet to said compression device, and an unload circuit flow control device disposed in said unload circuit refrigerant line;
sensing at least one operating characteristic of the refrigerant at at least one point in the refrigerant circuit;
modulating said expansion device to selectively meter liquid refrigerant flow from said flash tank receiver to said refrigerant heat absorption heat exchanger; and
positioning the unload circuit flow control device, in response to at least one of refrigerant discharge pressure sensed at an outlet of the refrigerant compression device and refrigerant discharge temperature sensed at an outlet of the refrigerant compression device, between an open position where at refrigerant passes through the unload circuit refrigerant line from an intermediate pressure stage of the compression device to suction pressure and a closed position whereat refrigerant flow through the unload circuit refrigerant line is blocked; device and refrigerant discharge temperature sensed at an outlet of the refrigerant
wherein positioning the unload circuit flow control device between an open position and a closed position comprises selectively positioning the unload circuit flow control device between an open position and a closed position to maintain said refrigerant vapor compression system operating at a discharge pressure below a preselected upper limit, wherein said preselected upper limit is the critical point pressure for carbon dioxide.

7. A refrigerant vapor compression system as recited in claim 1 wherein said controller is operative in response to the at least one system operating parameter sensed by the at least one sensor to selectively position the expansion device to maintain said refrigerant vapor compression system operating at a discharge pressure below the preselected upper limit.

8. A method as recited in claim 6 wherein modulating said expansion device comprises selectively positioning the expansion device between an open position and a closed position to maintain said refrigerant vapor compression system operating at a discharge pressure below the preselected upper limit.

Assignees

• Chen Yu H
• Duraisamy Suresh
• Liu Lucy Yi
• Scarcella Jason
• Asprovski Zvonko
• Lamendola Kursten
• Mitra Biswajit
• Carrier Corp

Inventors

• Chen Yu H
• Duraisamy Suresh
• Liu Lucy Yi
• Scarcella Jason
• Asprovski Zvonko
• Lamendola Kursten
• Mitra Biswajit

Classifications

• F25B2600/2513

  Expansion valves · CPC title

• Y02B30/741

  Cross-Sectional Technologies · mapped topic

• F25B2700/21152

  at the discharge side of the compressor · CPC title

• F25B2700/1931

  Discharge pressures · CPC title

• F25B2400/16

  Receivers · CPC title