Installation for storing and supplying liquid carbon dioxide as refrigerant, particularly for filling air conditioning systems
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Solution Overview
Problem
The high operating pressure and low critical point of carbon dioxide as a refrigerant pose demanding requirements for storage and supply systems, particularly in the automotive sector for air conditioning systems.
Innovation Solution
A system for storing and supplying liquid carbon dioxide (R744) is proposed, featuring a CO2 tank system, pressure increase station, air heater, buffer container with heating and cooling, and a CO2 recooler, designed to manage temperature and pressure effectively within specified ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If liquid carbon dioxide is stored and supplied at high operating pressure, then the refrigerant can be effectively used in air conditioning systems, but the system requirements become correspondingly demanding
Solution Approach 1:
The system is divided into multiple functional components: a storage tank for liquid CO2, a pressure boosting station with compressor, a buffer tank, and a recooler. Each component handles a specific aspect of pressure management, allowing the high operating pressure requirement to be met while distributing the complexity across modular units rather than requiring a single complex system
Solution Approach 2:
The storage tank pre-cools the liquid CO2 to temperatures between -25°C and -20°C before it reaches the pressure boosting station. This preliminary cooling action reduces the thermal load on subsequent components and ensures the refrigerant is in the optimal state for compression, thereby reducing overall system complexity
2Temperature
If the temperature is reduced to maintain liquid carbon dioxide storage, then the refrigerant remains in liquid phase, but the risk of dry ice formation increases when the triple point is undershot
Solution Approach 1:
Temperature sensors monitor the CO2 temperature throughout the system, and the control system automatically activates heating elements when temperatures approach the triple point threshold. This feedback mechanism ensures the temperature remains below the dry ice formation point while still maintaining liquid phase, thereby ensuring reliable operation
Solution Approach 2:
Heating elements and temperature monitoring are installed in advance in critical sections of the system where temperature drops could lead to triple point conditions. This preparatory protection ensures that even if cooling systems fail or ambient temperatures drop, dry ice formation is prevented before it can occur
3Object-affected harmful factors
If carbon dioxide is stored as liquid refrigerant, then environmental benefits are achieved with low GWP and ODP, but high operating pressure and low critical point present significant challenges
Solution Approach 1:
The system transforms the physical parameters of CO2 by pre-cooling it to -25°C to -20°C before compression. This parameter change allows the refrigerant to be compressed to the required operating pressure (60-70 bar) while remaining in liquid phase, enabling the use of environmentally friendly CO2 without requiring excessively complex high-pressure equipment
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 efficiently stores and supplies R744, ensuring optimal temperature and pressure conditions for use in automotive air conditioning systems, while being environmentally friendly and cost-effective.
Implementation Method 1
Liquid carbon dioxide is stored in the pressurized carbon dioxide tank system (1). Temperature and pressure typically range between -25 and -20 °C and 16 and 20 bar.
Implementation Method 2
The tank system can be double-walled with an inner stainless steel tank. The space between the walls can be filled with a highly insulating material and additionally maintained under high vacuum.
Implementation Method 3
This station pumps the CO2 into the downstream pipeline (6) and increases the pressure to the process-related required value, typically around 70 bar.
Implementation Method 4
After pressure increase, the CO2 is warmed to approximately ambient temperature using an air-heated heater (3)
Implementation Method 5
An integrated, redundant heating system and a chiller ensure compliance with the process parameters even under varying ambient temperatures.
Implementation Method 6
An integrated, redundant heating system and a chiller ensure compliance with the process parameters even under varying ambient temperatures.
Implementation Method 7
the liquid carbon dioxide is cooled to the desired temperature level directly before the filling system on the line via at least one recooling unit and at least one heat exchanger of the CO2 recooler or chiller (5)
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
A system for storing and supplying liquid carbon dioxide as a refrigerant comprises a carbon dioxide tank system with at least one storage tank in which liquid carbon dioxide can be stored at a temperature in a first temperature range and at a pressure in a first pressure range, and which has at least one inlet connection for supplying liquid carbon dioxide, e.g., from a tank truck, and at least one outlet connection; at least one pressure boosting station, which is connected at at least one inlet connection via a pipeline to the outlet connection of the storage tank and is designed to provide liquid carbon dioxide at an outlet connection of the pressure boosting station at a pressure increased compared to the first pressure range in a second pressure range;A temperature control arrangement comprising at least one carbon dioxide buffer storage tank connected directly or indirectly via at least one pipeline to the outlet port of the pressure boosting station, designed to hold liquid carbon dioxide in the carbon dioxide buffer storage tank at a temperature higher than the first temperature range in a second temperature range and at a pressure in a third pressure range; and at least one carbon dioxide recooler connected via at least one pipeline to an outlet port of the carbon dioxide buffer storage tank, designed to supply liquid carbon dioxide to at least one consumer via an outlet port at a temperature in a setpoint temperature range and at a pressure in a setpoint temperature range.