Cryostat Recirculation Cooling to Eliminate Liquid Nitrogen Refills
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Solution Overview
Problem
Conventional cryostat configurations relying on liquid nitrogen for cooling superconducting magnet coils are cumbersome, require frequent refilling, and disrupt measurements, especially in environments lacking infrastructure, and are inefficient in terms of helium consumption and vibration management.
Innovation Solution
Introducing a gaseous cooling medium at 60K and 1 bar pressure into the second container, cooled by a closed refrigeration circuit, which reduces the temperature below 60K, thereby eliminating the need for liquid nitrogen and lowering helium evaporation rates, allowing for continuous operation with reduced mechanical disturbances and flexible placement of the refrigerator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If liquid nitrogen is used to cool the second container for thermal shielding, then the heat input into the first container is minimized, but frequent refilling is required and measurements must be interrupted
Solution Approach 1:
The patent replaces the mechanical refilling system with an automated refrigeration system. A refrigerator with a cooling circuit is installed to continuously cool the second container, eliminating the need for manual liquid nitrogen refilling and interruptions to measurements. The system uses a coolant circulating through cooling lines to maintain the thermal shielding temperature automatically.
Solution Approach 2:
The patent implements continuous cooling of the second container through an automated refrigeration system that operates without interruption. The cooling circuit continuously circulates coolant to maintain the thermal shielding, ensuring uninterrupted operation and eliminating the periodic interruptions caused by liquid nitrogen refilling.
2Temperature
If liquid nitrogen refilling is performed frequently, then the thermal shielding temperature is maintained, but measurement interruptions occur and operational complexity increases
Solution Approach 1:
The patent replaces the periodic manual refilling operation with a continuous automated refrigeration system. The refrigerator with cooling circuits maintains the second container temperature continuously, eliminating the time losses associated with frequent measurement interruptions for refilling.
Solution Approach 2:
The refrigeration system is designed to automatically maintain the thermal shielding temperature without requiring external intervention or measurement interruption. The cooling circuit self-regulates to keep the second container at the required temperature, making the system self-sufficient and eliminating operational downtime.
3Ease of operation
If a closed refrigeration circuit with gaseous cooling medium is used in the second container, then liquid nitrogen refilling is eliminated, but the system complexity increases
Solution Approach 1:
The patent employs a multi-functional refrigeration system that serves multiple purposes: it cools the second container for thermal shielding, eliminates the need for liquid nitrogen handling, and provides continuous operation. The single refrigeration unit with cooling circuits integrates what would otherwise require separate systems, reducing overall operational complexity despite the added mechanical components.
4Temperature
If liquid nitrogen is used for cooling, then thermal shielding is effective, but helium evaporation rate increases due to higher temperature
Solution Approach 1:
The patent changes the temperature parameter of the second container from the liquid nitrogen temperature (77K) to a lower temperature achieved by the refrigeration system. This parameter change reduces the thermal gradient to the first container, thereby reducing the heat input and consequently the helium evaporation rate, while maintaining effective thermal shielding.
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 eliminates the need for liquid nitrogen, significantly reduces helium consumption, allowing for longer intervals between refills, minimizes vibrations, and enables more efficient and cost-effective cooling with flexible placement of the cooling system, enhancing operational stability and reducing maintenance.
Implementation Method 1
the cooling medium is cooled to an operating temperature of ≦60K by a refrigerator by means of a cooling circuit
Implementation Method 2
the second container is filled with liquid nitrogen for thermally shielding the first container
Implementation Method 3
This structure minimizes the heat input into the first container caused by radiation heat
Implementation Method 4
the operating temperature of which is kept below 5K by means of helium evaporation
Implementation Method 5
can be kept at an operating temperature of between 75 and 80K by means of nitrogen evaporation
Data Source
AI summary
A method for converting a cryostat configuration (1) having a first container (2) with a liquid helium bath (3) and a second container (6) which is filled with liquid nitrogen (7) is characterized in that a cooling medium (12) which is in a gaseous state at a temperature of 60K and a pressure of 1 bar, is introduced into the second container and is cooled by a refrigerator (16) by means of a cooling circuit (11), the coolant lines of which are guided into the second container, to an operating temperature of ≦60K. With this retrofit for existing cryostat configurations that utilize both liquid helium and also liquid nitrogen for cooling a superconducting coil, use of liquid nitrogen can be completely avoided and the evaporation rate of the liquid helium can also be considerably reduced without having to re-liquefy the cryogens used.