Cryogenic Vessel Compartment Design for Sub-Cooled HTS Operation
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Solution Overview
Problem
High temperature superconductor (HTS) devices face challenges in maintaining sub-cooled temperatures below the boiling point of liquid cryogen at atmospheric pressure, which requires continuous nitrogen supply, complex compressor systems, and introduces gas bubbles that affect electrical breakdown strength.
Innovation Solution
A thermally insulated vessel with a thermal insulation barrier dividing it into upper and lower compartments for pressure equalization, coupled with a cryogenic refrigerator to maintain the HTS below transition temperature, and a temperature controller to keep the liquid cryogen at or above its boiling point, preventing boiling and contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If suction pumping is used to lower the temperature of liquid nitrogen below its boiling point, then the critical current density of HTS conductor is improved, but gas bubbles are produced that adversely affect the electrical breakdown strength
Solution Approach 1:
The system is divided into two separate compartments: a lower compartment containing sub-cooled liquid nitrogen for HTS cooling, and an upper compartment containing gaseous nitrogen at atmospheric pressure. This segmentation allows the harmful boiling bubbles to be confined to the upper compartment while maintaining bubble-free conditions in the lower compartment where electrical breakdown strength is critical.
Solution Approach 2:
The liquid nitrogen acts as an intermediary medium that transfers heat from the HTS conductor to the upper compartment, where it boils and expands into gaseous nitrogen. This intermediary approach allows sub-cooling to be achieved without direct contact between the HTS conductor and boiling bubbles.
2Quantity of substance
If suction pumping is used to maintain sub-cooled temperature, then HTS critical current is improved, but continuous supply of liquid nitrogen or complex compressor and condenser systems are required
Solution Approach 1:
The system uses the natural boiling and expansion properties of nitrogen to maintain pressure balance. The lower compartment is sealed and self-contained, using the phase change of nitrogen itself to regulate pressure without requiring external compressors, condensers, or continuous liquid nitrogen supply.
Solution Approach 2:
The system exploits the phase transition of nitrogen from liquid to gas to maintain pressure equilibrium. As liquid nitrogen in the lower compartment absorbs heat and boils, it expands into the upper compartment, automatically maintaining pressure balance without mechanical intervention.
3Object-affected harmful factors
If the vessel is sealed to maintain pressure, then contamination from atmospheric oxygen and water vapor is prevented, but the vessel must withstand external atmospheric pressure
Solution Approach 1:
The pressure-bearing function is segmented from the containment function. The lower compartment is sealed and pressure-resistant, while the upper compartment is vented to atmosphere. This segmentation allows the critical HTS region to be protected from contamination without requiring the entire vessel to withstand high external pressure.
Solution Approach 2:
The upper compartment is maintained at atmospheric pressure, equalizing the pressure environment with the external atmosphere. This eliminates the pressure differential that would otherwise require the entire vessel to be pressure-resistant, reducing structural requirements.
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 allows for stable operation of HTS devices at improved critical current densities without the need for continuous nitrogen supply or non-condensable gases, maintaining a pressure above atmospheric pressure to prevent contamination and electrical breakdown issues.
Implementation Method 1
a cryogenic refrigerator has a cold head thermally coupled to the high temperature superconductor for maintaining the high temperature superconductor below a transition temperature for superconductivity
Implementation Method 2
a thermal insulation barrier disposed in the vessel and defining an upper compartment within the vessel above the barrier and a lower compartment within the vessel below the barrier
Implementation Method 3
the superconducting magnet often is immersed in liquid cryogen so that the liquid cryogen may boil off to absorb the heat
Data Source
AI summary
A thermally insulated vessel contains a thermal insulation barrier defining an upper compartment above the barrier and a lower compartment below the barrier. The compartments are interconnected by a passage to allow pressure equalization. High temperature superconductor is mounted within the lower compartment for immersion in the liquid cryogen. A cryogenic refrigerator has a cold head thermally coupled to the high temperature superconductor for maintaining the high temperature superconductor below a superconductive transition temperature. A temperature controller maintains a temperature of the liquid cryogen in the upper compartment at a temperature of at least a boiling point of the liquid cryogen at atmospheric pressure when the lower compartment and at least a portion of the upper compartment are filled with the liquid cryogen.