cryocooler
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Solution Overview
Problem
Ceramic-based magnetic regenerator materials in cryocoolers exhibit significant performance decreases due to temperature fluctuations caused by axial movement of the displacer, leading to a substantial decrease in specific heat and overall cryogenic performance.
Innovation Solution
A cryocooler design with a cylinder and cooling stages having different thermal conductivities, where the ceramic-based magnetic regenerator material's axial position overlaps with a stage tubular portion at the top dead center, ensuring it is surrounded by the cooling stage, thereby stabilizing its temperature and reducing temperature fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a ceramic-based magnetic regenerator material is used in a cryocooler, then the cooling capacity at cryogenic temperatures is improved, but the specific heat fluctuates significantly due to temperature variations caused by displacer movement
Solution Approach 1:
A thermal insulation layer is introduced as an intermediary between the ceramic-based magnetic regenerator material and the surrounding environment. This insulation layer acts as a mediator that blocks heat transfer paths, thereby stabilizing the temperature of the regenerator material despite the axial temperature distribution generated by the cryocooler itself during operation.
Solution Approach 2:
The patent employs a simple thermal insulation structure that can be easily manufactured and replaced if necessary. The insulation layer serves as a consumable protective element that maintains the thermal stability of the expensive ceramic regenerator material without requiring complex active control systems.
2Productivity
If the displacer moves axially to provide cooling, then the cryocooler operates, but the axial temperature distribution causes temperature fluctuation in the regenerator material
Solution Approach 1:
The cryocooler structure is segmented into distinct thermal zones. The thermal insulation layer creates a thermal boundary that separates the regenerator material from the axial temperature gradient generated during displacer movement. This segmentation allows the regenerator material to maintain a relatively stable temperature independent of the overall axial temperature distribution.
Solution Approach 2:
Thermal insulation is applied locally around the ceramic-based magnetic regenerator material rather than throughout the entire cryocooler. This localized insulation approach targets the specific region where temperature stability is critical, allowing the rest of the system to maintain the necessary axial temperature gradient for cooling operation.
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
The design effectively suppresses performance decreases in the cryocooler by stabilizing the ceramic-based magnetic regenerator material's temperature, enhancing the cryogenic performance and reducing heat generation from eddy currents.
Implementation Method 1
a magnetic regenerator material having a great specific heat peak associated with a magnetic phase transition in this temperature range
Implementation Method 2
a cooling stage that has a second thermal conductivity higher than the first thermal conductivity
Data Source
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AI summary
A performance decrease of a cryocooler (10) in which a ceramic-based magnetic regenerator material (28c) is built is suppressed. A cryocooler (10) includes a second cylinder (16b) that has a first thermal conductivity and that extends in an axial direction, a second cooling stage (35) that has a second thermal conductivity higher than the first thermal conductivity and that includes a stage end portion (35a) and a stage tubular portion (35b) connecting the stage end portion (35a) to the second cylinder (16b) in the axial direction, a second displacer (18b) that is capable of reciprocating in the axial direction in the second cylinder (16b), that forms a second expansion chamber (34) with the stage end portion (35a), and in which the second expansion chamber (34) takes a maximum volume at a top dead center, and a ceramic-based magnetic regenerator material (28c) that is accommodated in the second displacer (18b) and of which an axial position in the second displacer (18b) is determined to overlap the stage tubular portion (35b) in the axial direction when the second displacer (18b) is at the top dead center.