Systems and methods for cryogenic refrigeration
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Solution Overview
Problem
Current cryogenic refrigeration systems, particularly dilution refrigerators, face significant challenges with contaminant plugging due to the freezing of contaminants like nitrogen, oxygen, and carbon dioxide in helium circuits, leading to reliability issues and the need for frequent warm-ups, as existing filters and cold traps are not effective enough.
Innovation Solution
The implementation of a multi-trap system utilizing cryocondensation and cryoadsorption techniques, with dedicated traps at specific temperatures to target different contaminants, and the use of materials with high thermal conductivity and specific heat for cryocondensation surfaces, along with adsorptive materials like zeolite, to effectively trap contaminants without blocking the helium circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If mechanical pumps and compressors are used to circulate helium, then the dilution refrigerator can operate, but contaminants are added to the helium and freeze in the circuits causing blockages
Solution Approach 1:
The system divides the trapping function into multiple separate traps (first trap with cryocondensation surface, second trap with adsorptive material) positioned at different locations in the helium circuit, each targeting different contaminants at different temperatures
Solution Approach 2:
The patent introduces traps as intermediary components between the mechanical pumps/compressors and the delicate dilution refrigerator components, where contaminants are removed from the helium before reaching sensitive areas
2Reliability
If filters and cold traps are used to remove contaminants, then plugging frequency is reduced, but existing filters and traps are of limited effectiveness
Solution Approach 1:
The trapping system is segmented into multiple specialized traps rather than using a single general-purpose filter, with each trap designed for specific contaminant removal at specific temperature ranges
Solution Approach 2:
The system utilizes temperature as a key parameter, operating traps at different temperatures (e.g., 4K, 77K, room temperature) to optimize contaminant removal efficiency for different types of contaminants
3Reliability
If the dilution refrigerator is warmed up to remove contaminants, then blockages are cleared, but the process takes several days and disrupts operation
Solution Approach 1:
The traps continuously remove contaminants from the helium circuit in advance, preventing blockage formation before they occur, rather than requiring corrective warm-up actions after blockages develop
Solution Approach 2:
The trapping system operates continuously during normal refrigerator operation, maintaining constant contaminant removal without interrupting the cooling process or requiring warm-up cycles
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 frequency of plugging events, enabling continuous operation of dilution refrigerators for extended periods by effectively removing contaminants at specific temperatures, minimizing helium trapping, and enhancing the overall performance and reliability of cryogenic refrigeration systems.
Implementation Method 1
the first trap comprises a first trap volume and at least one cryocondensation surface inside the first trap volume
Implementation Method 2
the second trap comprises a second trap volume and an adsorptive material inside the second trap volume
Data Source
AI summary
Systems and methods for improving the performance of dilution refrigeration systems are described. Filters and traps employed in the helium circuit of a dilution refrigerator may be modified to improve performance. Some traps may be designed to harness cryocondensation as opposed to cryoadsorption. A cryocondensation trap employs a cryocondensation surface having a high thermal conductivity and a high specific heat with a binding energy that preferably matches at least one contaminant but does not match helium. Multiple traps may be coupled in series in the helium circuit, with each trap designed to trap a specific contaminant or set of contaminants. Both cryocondensation and cryoadsorption may be exploited among multiple traps.