Co2 refrigeration system with superheat control
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Solution Overview
Problem
Existing refrigeration systems using carbon dioxide as a refrigerant face challenges in efficiently managing superheat and preventing liquid return to compressors, leading to inefficiencies and operational envelope limitations.
Innovation Solution
A transcritical refrigeration system with a superheat control system that includes a heat exchanger and valve system, controlled by a controller, to manage the flow of refrigerant and maintain optimal superheat levels, preventing liquid return to compressors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional vapor compression cycle is used with CO2 refrigerant, then the system can provide cooling through evaporation, but liquid refrigerant may return to the compressor causing operational issues and efficiency losses
Solution Approach 1:
The superheat control system performs preliminary action by heating the refrigerant in the evaporator outlet line before it enters the compressor. The control valve regulates refrigerant flow through the superheat coil, ensuring the refrigerant is fully vaporized and superheated before compression, preventing liquid return to the compressor.
Solution Approach 2:
A superheat coil acts as an intermediary component between the evaporator outlet and the compressor suction inlet. This intermediate heat exchanger provides the necessary heating function to ensure proper vaporization and superheating of the refrigerant before it enters the compressor, isolating the compressor from potential liquid refrigerant.
2Adaptability or versatility
If the refrigeration system operates under varying environmental conditions, then adaptability is improved, but maintaining optimal superheat levels becomes more difficult
Solution Approach 1:
The superheat control system employs feedback control by continuously monitoring the refrigerant temperature and pressure at the evaporator outlet and compressor suction inlet. The control valve adjusts the refrigerant flow through the superheat coil based on this feedback, maintaining optimal superheat levels despite varying environmental conditions, evaporator loads, or refrigerant properties.
3Loss of energy
If flash gas production is reduced through better refrigerant management, then energy efficiency is improved, but system complexity increases
Solution Approach 1:
The system controls flash gas production by changing the temperature parameter of the refrigerant through superheating. By maintaining the refrigerant temperature above the saturation temperature at the evaporator outlet pressure, the system prevents flash gas formation in the suction line. The control valve adjusts refrigerant flow to maintain optimal superheat, thereby controlling flash gas production and improving energy efficiency.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system enhances energy efficiency, prevents liquid return to compressors, reduces flash gas production, and allows operation under varying environmental conditions, thereby improving overall system performance.
Implementation Method 1
a heat exchanger system including a first side configured to carry gas refrigerant passing between the gas cooler/condenser and an inlet of the receiver, and a second side in heat transfer communication with the first side
Implementation Method 2
a valve system including one or more valves. The valve system is configured to circulate gas refrigerant from the medium temperature evaporator outlet of at least one of the medium temperature evaporators such that at least a portion of the gas refrigerant passes through the second side of the heat exchanger
Implementation Method 3
one or more transcritical compressors operable to compress gas refrigerant and discharge the compressed gas refrigerant into a discharge line
Implementation Method 4
cooled/condensed to a lower temperature state (e.g., in a gas cooler or condenser which absorbs heat from the refrigerant)
Implementation Method 5
expanded to a lower pressure (e.g., through an expansion valve)
Implementation Method 6
evaporated to provide cooling by absorbing heat into the refrigerant
Data Source
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AI summary
A transcritical refrigeration system (100, 300, 400, 500, 600, 700) includes a gas cooler/condenser (102); a receiver (108) configured to collect refrigerant produced by the refrigeration system (100, 300, 400, 500, 600, 700); a gas bypass valve (110) fluidly coupled to the outlet of the receiver (108) and operable to control a pressure of the refrigerant in the receiver (108); and a medium temperature subsystem (112, 504, 608, 704). The medium temperature subsystem (112, 504, 608, 704) includes one or more expansion valves (140); one or more medium temperature evaporators (142); and a suction group (514, 714) including one or more transcritical compressors (144, 516, 613, 616, 716) operable to compress gas refrigerant and discharge the compressed gas refrigerant into a discharge line. The system includes a superheat control system (104, 304, 404, 506, 604, 706) that includes a heat exchanger system (116, 520, 522, 610, 720, 722) including a first side configured to carry gas refrigerant passing between the gas cooler/condenser (102) and an inlet of the receiver (108), and a second side in heat transfer communication with the first side.