CO2 Subcooling Control for Refrigerant Pressure Relief
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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
1Stress or pressure
If heat removal from CO2 refrigerant is insufficient, then refrigerant pressure increases, but CO2 refrigerant must be released and refilled
Solution Approach 1:
The system divides heat removal into two separate heat exchangers: a first heat exchanger for primary cooling and a second heat exchanger for subcooling. This segmentation allows the system to remove heat in stages, effectively controlling refrigerant pressure without releasing CO2
Solution Approach 2:
The subcooling system activates before pressure becomes critical by monitoring temperature and pressure thresholds. By performing preliminary heat removal when conditions are still manageable, the system prevents the need for refrigerant release and refilling
2Stress or pressure
If a subcooling system is added to remove additional heat, then pressure control improves, but device complexity increases
Solution Approach 1:
The second heat exchanger serves multiple functions: it acts as a subcooling device for the CO2 refrigerant and also functions as a condenser for a second refrigerant. This multi-functionality adds pressure control capability without proportionally increasing system complexity
Solution Approach 2:
The system uses itself to provide subcooling by having the second refrigerant cycle through the second heat exchanger, where it absorbs heat from the CO2 refrigerant. This self-service approach eliminates the need for a completely separate cooling system
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 during warm or hot conditions.
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 condenser removes heat from a second refrigerant
Implementation Method 4
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
Implementation Method 5
The first compressor compresses the carbon dioxide refrigerant and sends the compressed carbon dioxide refrigerant to the first heat exchanger
Implementation Method 6
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 subcooling controller includes a sensor and a processor. The sensor measures one or more of a temperature external to a first heat exchanger that removes heat from carbon dioxide refrigerant, a temperature of the carbon dioxide refrigerant, and a pressure of the carbon dioxide refrigerant. The processor determines that one or more of the measured temperature external to the first heat exchanger, the temperature of the carbon dioxide refrigerant, and the pressure of the carbon dioxide refrigerant is above a threshold and in response to that determination, activates a subcooling system. The subcooling system includes a condenser, a second heat exchanger, and a compressor. The condenser removes heat from a second refrigerant. The second heat removes heat from the carbon dioxide refrigerant stored in a flash tank. The compressor compresses the second refrigerant from the second heat exchanger and sends the second refrigerant to the condenser.