CO2 Refrigerant Subcooling System for Pressure Control Without Release
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Solution Overview
Problem
Carbon dioxide (CO2) refrigerant systems face challenges in maintaining safe pressure levels due to increased pressure in refrigerant lines when heat removal becomes difficult, often requiring refrigerant release and subsequent refilling.
Innovation Solution
A subcooling system is integrated into the CO2 refrigerant system, utilizing a separate coolant, condenser, compressor, and heat exchanger to remove additional heat from the CO2 refrigerant when temperature and pressure thresholds are exceeded, thereby reducing pressure in the refrigerant line without releasing CO2.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional cooling system cycles refrigerant to cool a space, then cooling function is provided, but when heat removal becomes difficult, pressure in the refrigerant line increases to unsafe levels requiring refrigerant release
Solution Approach 1:
The system divides the single refrigerant cycle into two separate loops: a primary CO2 refrigerant loop and a secondary coolant loop. The CO2 loop handles space cooling, while the secondary loop with its own condenser and heat exchanger handles refrigerant pressure control. This segmentation allows independent optimization of each loop's function.
Solution Approach 2:
A secondary coolant acts as an intermediary substance between the CO2 refrigerant and the environment. The coolant absorbs excess heat from the CO2 refrigerant through heat exchangers, mediating the heat transfer process and enabling pressure control without directly modifying the CO2 refrigerant cycle.
2Stress or pressure
If refrigerant is released to decrease pressure, then pressure safety is maintained, but the refrigerant must be refilled at a later time
Solution Approach 1:
The system continuously removes heat from the CO2 refrigerant through the secondary cooling loop before pressure reaches dangerous levels. This preliminary heat removal action prevents the need for emergency refrigerant discharge and subsequent refilling operations.
Solution Approach 2:
The secondary coolant circulates continuously through its own cycle, constantly absorbing heat from the CO2 refrigerant and maintaining pressure within safe operating parameters. This continuous action eliminates intermittent refrigerant loss and refilling requirements.
3Reliability
If additional heat removal capacity is added to the CO2 system, then pressure control is improved, but device complexity increases with separate coolant cycle components
Solution Approach 1:
The secondary coolant cycle serves multiple functions: it cools the CO2 refrigerant, provides an independent heat rejection path, and can operate autonomously without interfering with the primary cooling cycle. This multi-functionality justifies the additional components by delivering multiple benefits from a single system addition.
Solution Approach 2:
The system merges two complete refrigerant cycles into one integrated pressure control solution. By combining the CO2 refrigerant loop with a secondary coolant loop that includes its own compressor, condenser, and heat exchanger, the system achieves robust pressure control while maintaining operational independence of each cycle.
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 subcooling system maintains safe pressure levels in the CO2 refrigerant line, reducing the frequency of CO2 refilling and replacement by efficiently removing heat, especially on warm or hot days when CO2 refrigerant pressure would otherwise rise to unsafe levels.
Implementation Method 1
The first heat exchanger removes heat from carbon dioxide refrigerant
Implementation Method 2
The condenser removes heat from a second refrigerant
Implementation Method 3
The second heat exchanger removes heat from the carbon dioxide refrigerant stored in the flash tank
Implementation Method 4
The first compressor compresses the carbon dioxide refrigerant and sends the compressed carbon dioxide refrigerant to the first heat exchanger
Implementation Method 5
The second compressor compresses the second refrigerant from the heat exchanger. The second compressor sends the second refrigerant to the condenser
Data Source
AI summary
A system includes a first heat exchanger, a flash tank, a first compressor, a condenser, a second heat exchanger, and a second compressor. The first heat exchanger removes heat from carbon dioxide refrigerant. The flash tank stores the carbon dioxide refrigerant from the first heat exchanger. The first compressor compresses the carbon dioxide refrigerant and sends the compressed carbon dioxide refrigerant to the first heat exchanger. The condenser removes heat from a second refrigerant. The second heat exchanger receives the second refrigerant from the condenser. The second heat exchanger further removes heat from the carbon dioxide refrigerant stored in the flash tank. The second compressor compresses the second refrigerant from the heat exchanger. The second compressor sends the second refrigerant to the condenser.