CO2 Subcooling Loop for Refrigerant Pressure Control
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Solution Overview
Problem
Carbon dioxide (CO2) refrigerant systems face challenges in removing sufficient heat, leading to increased pressure in refrigerant lines, which can become unsafe and require frequent refrigerant refill when heat removal is difficult on warm or hot days.
Innovation Solution
A CO2 cooling system incorporating a subcooling system that uses a separate coolant, condenser, compressor, and heat exchanger to remove additional heat from the CO2 refrigerant when temperature and pressure thresholds are exceeded, maintaining safe pressure levels without refrigerant release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a standard cooling system cycles refrigerant to cool a space, then cooling function is provided, but when the system is unable to remove heat from the refrigerant, pressure in the refrigerant line increases to unsafe levels
Solution Approach 1:
The cooling system is divided into two separate loops: a primary loop using CO2 refrigerant for space cooling, and a secondary subcooling loop using a different refrigerant specifically dedicated to removing excess heat from the CO2 refrigerant. This segmentation allows the subcooling loop to focus exclusively on heat removal without being constrained by the cooling demands of the primary loop, thereby preventing pressure buildup in the CO2 refrigerant line.
Solution Approach 2:
A second refrigerant is introduced as an intermediary substance in the subcooling loop. This intermediary refrigerant absorbs excess heat from the CO2 refrigerant through the heat exchanger, acting as a mediator that transfers thermal energy from the CO2 system to the environment. This intermediary mechanism enables effective heat removal that prevents dangerous pressure increases in the CO2 refrigerant line.
2Stress or pressure
If refrigerant is released from the system to decrease pressure, then pressure in the refrigerant line is reduced, but the refrigerant would have to be refilled at a later time
Solution Approach 1:
The subcooling loop performs preliminary heat removal from the CO2 refrigerant before it can accumulate enough heat to require pressure relief through refrigerant discharge. By continuously removing excess heat in advance, the system prevents the conditions that would lead to refrigerant loss, eliminating the need for frequent refilling operations.
Solution Approach 2:
The system converts the potentially harmful effect of heat accumulation (which leads to pressure buildup and refrigerant loss) into a beneficial process by using the subcooling loop to deliberately remove this excess heat. The heat that would otherwise be harmful is now systematically extracted through the second heat exchanger, transforming a problem into a controlled solution that preserves refrigerant quantity.
3Stress or pressure
If a subcooling system is added to remove additional heat from CO2 refrigerant, then pressure levels are maintained safely, but device complexity increases with additional components
Solution Approach 1:
The second heat exchanger serves multiple functions: it acts as a heat transfer surface for the subcooling loop, a condenser for the second refrigerant, and a pressure control mechanism for the CO2 refrigerant line. By designing this component to perform multiple roles, the patent reduces the need for separate dedicated components for each function, thereby mitigating the increase in device complexity while still achieving effective pressure control.
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 reduces the need for frequent refrigerant refills by maintaining safe pressure levels in the CO2 refrigerant line, enhancing cooling system efficiency and reducing the refill rate.
Implementation Method 1
a first heat exchanger that removes heat from carbon dioxide refrigerant
Implementation Method 2
The condenser removes heat from a second refrigerant
Implementation Method 3
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 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 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.