Rare-Earth Regenerator Particles With Surface Depressions for Helium Flow
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Solution Overview
Problem
Conventional regenerator materials for cryogenic refrigerators face challenges in achieving high-density filling and maximizing the contact surface area with the operating medium gas, such as helium, which affects the refrigerating performance and reliability of superconducting applications like MRI and semiconductor manufacturing.
Innovation Solution
Rare-earth regenerator material particles with specific size and shape characteristics, including an average particle size of 0.01 to 3 mm, a high proportion of particles with an aspect ratio of 2 or less, and depressed portions on their surface, are developed to enhance packing density and contact surface area, utilizing manufacturing methods like the Rotary Disc Process and rotary nozzle processes under controlled conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If spherical particles are used for high-density filling, then packing density is improved, but contact surface area with He gas is reduced
Solution Approach 1:
The patent applies asymmetry by transitioning from spherical particles to particles with depressed portions on their surfaces. This asymmetric surface modification increases the contact surface area with He gas while maintaining high packing density, as the depressed portions create additional surface area without significantly increasing particle volume or disrupting the close-packing arrangement.
Solution Approach 2:
The depressed portions on particle surfaces create a porous-like surface structure that increases the effective contact area with He gas. This surface porosity allows for greater gas-particle interaction while maintaining the overall particle density and packing efficiency needed for high-performance regenerator operation.
2Quantity of substance
If smaller particles are used to fill spaces between larger particles, then packing density is improved, but He gas permeability is reduced
Solution Approach 1:
The patent applies local quality by modifying only the surface of each particle with depressed portions, rather than changing the overall particle size distribution. This localized surface modification increases contact area without requiring smaller particles, thereby maintaining the pore spaces and permeability pathways necessary for He gas flow while enhancing the gas-particle contact surface area.
3Quantity of substance
If particles are filled under high pressure to increase density, then packing density is improved, but particle crushing and clogging occur
Solution Approach 1:
The patent applies preliminary action by pre-forming the depressed portions on particle surfaces during the manufacturing process, before the particles are subjected to filling operations. This preliminary surface structuring allows particles to achieve high packing density through their inherent shape characteristics without requiring excessive filling pressure, thereby preventing particle crushing and maintaining structural integrity.
Data Source
AI summary
Provided is a group of rare-earth regenerator material particles having an average particle size of 0.01 to 3 mm, wherein the proportion of particles having a ratio of a long diameter to a short diameter of 2 or less is 90% or more by number, and the proportion of particles having a depressed portion having a length of 1/10 to ½ of a circumferential length on a particle surface is 30% or more by number. By forming the depressed portion on the surface of the regenerator material particles, it is possible to increase permeability of an operating medium gas and a contact surface area with the operating medium gas.