Cryogenic cooling system with plural mechanical refrigerators
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Solution Overview
Problem
Cryostats face challenges in managing larger heat loads, which limits the rate at which helium can flow to the coldest parts and prevents effective pre-cooling and condensation, due to the finite cooling power of pulse tubes, especially as temperature decreases.
Innovation Solution
A cryogenic cooling system that uses a dedicated mechanical refrigerator with multiple stages to pre-cool and condense helium, where the coldest stage is used to further cool helium pre-cooled by a thermally more loaded refrigerator, allowing for a more efficient heat load distribution and increased flow rate to the coldest parts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single mechanical refrigerator is used to cool helium, then the cooling power is sufficient at higher temperatures, but the cooling power becomes insufficient at lower temperatures, limiting the flow rate of helium to the coldest parts
Solution Approach 1:
The cooling system is divided into multiple independent mechanical refrigerators, each responsible for specific temperature ranges. The first mechanical refrigerator handles the warmer temperature stages, while the second mechanical refrigerator handles the coldest stages. This segmentation allows each refrigerator to operate within its optimal temperature range, maintaining sufficient cooling power across the entire temperature spectrum and enabling higher helium flow rates to the coldest parts.
2Power
If more cooling power is provided to handle larger heat loads, then the cooling capacity increases, but the system complexity increases
Solution Approach 1:
Instead of using a single complex refrigerator with excessive cooling power, the system uses multiple simpler refrigerators with moderate cooling power, each optimized for specific temperature ranges. This segmentation reduces the complexity of individual units while achieving the required total cooling capacity.
Solution Approach 2:
Each mechanical refrigerator is designed to perform multiple functions: cooling the helium stream, maintaining temperature stability, and providing headroom for heat load variations. This multi-functionality reduces the need for additional specialized components, thereby limiting system complexity.
3Productivity
If the cooling power is increased to maintain higher flow rates, then the helium flow rate increases, but the pre-cooling and condensation efficiency decreases
Solution Approach 1:
The pre-cooling and condensation process is segmented into multiple stages, with each mechanical refrigerator responsible for specific temperature ranges. The first refrigerator performs initial cooling and partial condensation, while the second refrigerator completes the cooling and condensation process. This segmentation allows each stage to operate at optimal conditions, maintaining high pre-cooling and condensation efficiency even at elevated flow rates.
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 solution enables helium to reach lower temperatures, improves the efficiency of pre-cooling and condensation, and increases the rate at which helium can flow to the coldest parts of the cryostat, addressing the limitations of existing systems.
Implementation Method 1
at least one thermal coupling of said first conduit and said first mechanical refrigerator for cooling said fluid cooling medium on its way towards said working region
Data Source
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AI summary
A cryogenic cooling system comprises a vacuum enclosure. A first mechanical refrigerator comprises first upper (104) and lower (106) cooling stages in said vacuum enclosure. A first conduit (402) passes a first stream of fluid cooling medium towards a working region. At least one thermal coupling (403) of said first conduit (402) and said first mechanical refrigerator (401) cools said fluid cooling medium on its way towards said working region. A second mechanical refrigerator (404) comprises second upper (405) and lower (406) cooling stages in said vacuum enclosure. At least one thermal coupling (407) of said first conduit (402) and said second mechanical refrigerator (404) cools said fluid cooling medium further after said at least one thermal coupling (403) of said first conduit (402) and said first mechanical refrigerator (401) on the path of said first stream of fluid cooling medium.