Thermal management systems
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Solution Overview
Problem
Conventional closed-circuit refrigeration systems are heavy and power-intensive, making them impractical for applications with size and weight constraints, and ammonia refrigerants pose disposal challenges due to toxicity.
Innovation Solution
The development of thermal management systems that integrate open-circuit refrigeration systems (OCRSs) with closed-circuit refrigeration systems (CCRSs), using supercritical carbon dioxide (CO2) as a refrigerant, which operates in sub-critical, trans-critical, or supercritical modes, allowing for safe discharge and efficient cooling without the need for heavy compressors and condensers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional closed-circuit refrigeration systems are used to handle absorbed thermal energy, then cooling capacity is achieved, but system weight increases and power consumption increases
Solution Approach 1:
The patent extracts the compressor and condenser components from the refrigeration system, transitioning from a closed-circuit to an open-circuit configuration. This removal of heavy power-consuming components directly addresses the contradiction by eliminating the source of high power consumption and weight while maintaining cooling functionality through direct refrigerant discharge to the environment.
Solution Approach 2:
The system employs a disposable refrigerant charge that is discharged into the environment after use, rather than being continuously circulated. This approach eliminates the need for heavy durable components like compressors and condensers, accepting that the refrigerant will be consumed and discharged, thereby reducing system weight and power requirements.
2Productivity
If ammonia is used as refrigerant fluid in open-circuit systems, then cooling efficiency is improved, but disposal becomes problematic due to toxicity
Solution Approach 1:
The patent changes the chemical parameter of the refrigerant fluid from ammonia to carbon dioxide. This parameter change maintains the open-circuit system's cooling efficiency while eliminating the toxicity issue, as CO2 is non-toxic and can be safely discharged into the environment without harmful effects.
3Duration of action of moving object
If receiver size is increased to extend operation period in open-circuit systems, then operating duration is improved, but system volume and weight increase
Solution Approach 1:
The system operates in periodic cycles where refrigerant is discharged, provides cooling, and then the system can be recharged. This periodic operation allows for a smaller receiver volume while maintaining adequate operating duration, as the system does not require continuous large-scale refrigerant storage but rather periodic replenishment.
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 reduces the overall size and weight of refrigeration systems, accurately matches temperature set points, and safely discharges refrigerant vapor, providing efficient cooling for high heat loads while avoiding the disposal issues associated with ammonia.
Implementation Method 1
The expansion valve is configured to expand refrigerant from the receiver to an ambient pressure that is below the triple point pressure of the refrigerant fluid to turn the refrigerant into a solid state
Implementation Method 2
The evaporator is configured to receive the solid state of the refrigerant and to extract heat from a heat load that contacts or is in proximity to the evaporator to sublime the solid state of the refrigerant directly into a vapor state of the refrigerant
Implementation Method 3
Refrigeration systems absorb thermal energy from the heat sources and discharge thermal energy into the surrounding environment
Data Source
AI summary
Thermal management techniques include: transporting a refrigerant fluid from a receiver to an inlet of a flash tank that has a vapor-side outlet and liquid-side outlet such that a liquid phase of the refrigerant fluid moves to a bottom of the flash tank and outputs from the liquid-side outlet; forming a solid-vapor state from the liquid phase by expanding the liquid phase with an expansion valve to a first pressure that is less than a triple point pressure to form a solid-vapor mixture of the refrigerant fluid; extracting heat from a heat load with an evaporator that receives the solid-vapor mixture of the refrigerant fluid and sublimates the solid state of the solid-vapor mixture of the refrigerant fluid directly into a vapor phase of the refrigerant fluid; and discharging, from an exhaust line, the vapor phase to an ambient environment without returning the vapor phase to the receiver.