Liquid Oxygen Densification Cycle Using JT Expansion Refrigerant Mix
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Solution Overview
Problem
Current cryogenic refrigeration systems for propellant densification, such as liquid oxygen, face challenges in reducing operational and capital costs, as well as the time required to achieve desired temperatures, necessitating improved refrigeration cycles.
Innovation Solution
A closed-loop Joule-Thompson expansion valve or turbine-based refrigeration system using a mixture of neon or helium with nitrogen and/or oxygen as the working fluid, which compresses, cools, expands, and recirculates the fluid to subcool liquid oxygen to temperatures below 66.5 K, optimizing the refrigeration cycle for efficient densification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional cryogenic refrigeration systems are used for liquid oxygen densification, then the system can achieve propellant densification, but the operational and capital costs are high and the time required to achieve desired temperatures is excessive
Solution Approach 1:
The patent changes the thermodynamic parameters of the refrigeration cycle by using a two-stage expansion process with interstage cooling. The first expansion stage operates at a higher pressure ratio, followed by interstage cooling to reset the temperature, then a second expansion stage. This parameter optimization enables faster cooling rates while maintaining energy efficiency, directly addressing the contradiction between productivity and time loss.
Solution Approach 2:
The refrigeration cycle is segmented into distinct stages: first expansion, interstage cooling, and second expansion. This segmentation allows each stage to be optimized independently, with the interstage cooling serving as a reset point that enables faster overall cooling while managing thermal loads efficiently. The segmentation resolves the contradiction by breaking the continuous cooling process into manageable phases that can be executed more rapidly.
2Ease of manufacture
If conventional refrigeration cycles are used, then the system structure is relatively simple, but the operational and capital costs are high
Solution Approach 1:
The patent utilizes phase transitions of the working fluid during the expansion processes. The two-stage expansion with interstage cooling leverages the phase change characteristics of the refrigerant to achieve efficient heat transfer and cooling. This approach improves operational efficiency and reduces energy consumption compared to conventional single-stage systems, while the added complexity remains manageable due to the use of well-understood phase transition physics.
3Productivity
If a single-stage expansion system is used, then the device complexity is low, but the cooling efficiency and speed are insufficient
Solution Approach 1:
The interstage cooling acts as a preliminary action between the two expansion stages. By cooling the working fluid between expansions, the system prepares the refrigerant for the second expansion stage, enabling faster and more efficient cooling overall. This preliminary action justifies the increased device complexity by delivering superior cooling performance that cannot be achieved with single-stage expansion.
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 time and cost associated with achieving low temperatures for liquid oxygen densification, offering a balance between power efficiency and capital costs, while managing the challenges of fluid phase changes and refrigerant mixtures.
Implementation Method 1
compressing a working fluid having between 70 mol % and 80 mol % neon or neon and helium and between 20 mol % and 30 mol % nitrogen and/or oxygen in a multistage compressor from a pressure just above ambient pressure to a pressure between about 150 psia and 380 psia
Implementation Method 2
cooling the compressed working fluid via indirect heat exchange with a cold gaseous nitrogen stream or a liquid nitrogen stream or both to produce a cold, compressed working fluid
Implementation Method 3
expanding the cold, compressed working fluid in a JT expansion valve to produce a refrigeration stream of expanded working fluid at a temperature less than 66.5 K
Implementation Method 4
subcooling a stream of liquid oxygen via indirect heat exchange with the expanded working fluid to produce a densified liquid oxygen stream
Data Source
AI summary
Closed-loop refrigeration cycles for liquid oxygen densification are disclosed. The disclosed refrigeration cycles may be turbine-based refrigeration cycles or a Joule-Thompson (JT) expansion valve based refrigeration cycles and include a refrigerant or working fluid comprising a mixture of neon or helium together with nitrogen and/or oxygen.