Two-Stage Cryogenic Refrigeration for Liquid Oxygen Densification
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Solution Overview
Problem
Current liquid oxygen densification systems for space vehicle launches face logistical challenges due to the large volumes of liquid nitrogen required for cooling, leading to increased operational and capital costs, as well as waste nitrogen vented to the atmosphere, and inefficiencies in transporting cryogenic liquids to launch facilities.
Innovation Solution
A two-stage integrated densification system using a nitrogen-based reverse Brayton cycle refrigeration stage and a helium or neon-based second refrigeration stage to subcool and densify liquid oxygen, reducing the need for liquid nitrogen transport by utilizing a more efficient refrigeration cycle that recycles nitrogen refrigerant streams and uses indirect heat exchange to achieve temperatures between 70 Kelvin and 57 Kelvin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid nitrogen is used for cooling liquid oxygen in current densification systems, then cooling is achieved, but the volume and weight of nitrogen transport requirements increase significantly
Solution Approach 1:
The patent changes the thermodynamic parameters of the refrigeration process by implementing a two-stage system with inter-stage heat exchange. The first stage pre-cools the liquid oxygen using nitrogen refrigerant, while the second stage uses a different refrigerant cycle to achieve the final densification temperature. This parameter optimization reduces the quantity of liquid nitrogen required while achieving the same cooling effect.
Solution Approach 2:
The patent merges the cooling function with the refrigeration cycle by integrating heat exchangers that recover cold from the nitrogen refrigerant stream. The inter-stage heat exchanger combines the cooling effects of both refrigeration stages, allowing the system to achieve densification with reduced refrigerant volume by utilizing the cold content already present in the nitrogen stream.
2Temperature
If liquid nitrogen is transported to the launch facility for densification, then cooling capability is provided, but logistical burden and operational costs increase
Solution Approach 1:
The patent optimizes the refrigeration cycle parameters to reduce the quantity of liquid nitrogen required for the densification process. By implementing a two-stage system with heat recovery, the system achieves the same cooling effect with less refrigerant, thereby reducing transport logistics and operational complexity.
3Temperature
If excessive liquid nitrogen is used for densification, then cooling is achieved, but waste nitrogen vented to the atmosphere increases
Solution Approach 1:
The patent recovers the cold content from the nitrogen refrigerant stream through inter-stage heat exchange before the nitrogen is vented or recycled. The heat exchangers capture the cooling effect that would otherwise be wasted, allowing the system to achieve densification while minimizing the amount of nitrogen that needs to be discarded or requiring less replacement nitrogen.
Solution Approach 2:
The patent implements a feedback mechanism where the cold content of the nitrogen refrigerant stream is utilized in the second stage of the refrigeration cycle. The nitrogen that has performed its cooling function in the first stage is directed through heat exchangers to provide additional cooling in the second stage, creating a feedback loop that reduces overall nitrogen consumption and waste.
4Volume of moving object
If liquid oxygen is densified to smaller volume, then tank size is reduced, but the complexity of the densification system increases
Solution Approach 1:
The patent divides the densification process into two distinct stages, each with its own refrigeration cycle and heat exchangers. The first stage handles pre-cooling with nitrogen refrigerant, while the second stage completes the densification process. This segmentation allows each stage to be optimized independently and simplifies the overall system design by breaking down the complex single-stage process into manageable modules.
Solution Approach 2:
The patent introduces inter-stage heat exchangers as intermediary components that transfer cold from the first refrigeration stage to the second stage. These heat exchangers act as mediators that couple the two stages efficiently, allowing the system to achieve the desired densification while maintaining modular architecture and reducing overall system complexity through functional decomposition.
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
This approach significantly reduces the volume and weight of oxygen tanks needed, minimizing logistical burdens and operational costs by producing a densified liquid oxygen stream that can be transported efficiently to launch platforms, while eliminating the need for excessive nitrogen transport and waste.
Implementation Method 1
a first refrigeration stage configured to receive flow a nitrogen refrigerant through at least one first heat exchanger
Implementation Method 2
The first refrigeration stage is a nitrogen based reverse Brayton cycle refrigeration cycle configured to provide refrigeration
Implementation Method 3
flow a helium or neon containing second refrigerant through a second heat exchanger configured to cool the helium or neon containing second refrigerant via indirect heat exchange with one or more streams of the nitrogen refrigerant
Implementation Method 4
flow the helium or neon containing second refrigerant through a densification heat exchanger to subcool and densify the liquid oxygen stream
Data Source
AI summary
A system and method for the production and supply of a densified, liquid oxidant to a space vehicle launch facility is provided. A stream of liquid oxygen taken from a co-located, liquid producing air separation unit is densified in a two refrigeration stage, integrated densification system. The first refrigeration stage is a nitrogen based reverse Brayton cycle refrigeration cycle that provides refrigeration to the second refrigeration stage. The second refrigeration stage is a helium and/or neon comprising refrigerant loop that densifies the liquid oxygen to a temperature between about 70 Kelvin and 57 Kelvin. The integrated densification system may also be configured to densify liquid methane or other propellants used in space vehicle launches.