cryocooler
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Solution Overview
Problem
Cryocoolers using ceramic-based magnetic regenerator materials face performance decreases due to significant specific heat fluctuations caused by slight temperature fluctuations, especially in Gifford-McMahon cryocoolers.
Innovation Solution
A cryocooler design that includes a cylinder with a first thermal conductivity, a cooling stage with a higher thermal conductivity, a displacer capable of reciprocating within the cylinder, and a ceramic-based magnetic regenerator material positioned to overlap the stage tubular portion at the top dead center, stabilizing the temperature of the regenerator material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a ceramic-based magnetic regenerator material is used to improve cooling capacity at cryogenic temperatures, then the specific heat peak is extremely sharp which enhances cooling performance, but slight temperature fluctuations cause significant specific heat variations leading to performance decrease
Solution Approach 1:
The patent introduces a temperature stabilizing structure as an intermediary between the ceramic-based magnetic regenerator material and the thermal environment. This stabilizing structure acts as a buffer that reduces the direct impact of temperature fluctuations on the regenerator material, thereby maintaining more stable specific heat characteristics while preserving the sharp peak's cooling enhancement capability
Solution Approach 2:
The patent modifies the thermal parameters of the system by controlling the thermal conductivity and heat capacity of surrounding structures. By adjusting these thermal parameters, the system maintains the regenerator material's temperature within a narrower range, preventing excessive specific heat variations while preserving the beneficial sharp specific heat peak effect
2Productivity
If the displacer moves axially to enable refrigeration cycle operation, then the expansion space volume changes to produce cooling effect, but axial temperature distribution causes temperature fluctuation in the regenerator material
Solution Approach 1:
The patent segments the thermal management function by separating the displacer's mechanical reciprocation function from the thermal stabilization function. The temperature stabilizing structure is introduced as a distinct component that handles thermal stabilization independently, allowing the displacer to focus on volume change for refrigeration while the stabilizing structure manages temperature fluctuations
Solution Approach 2:
The patent implements preliminary thermal stabilization by positioning the temperature stabilizing structure in advance to preemptively counteract temperature fluctuations. This structure is designed to anticipate and compensate for temperature variations that would otherwise occur during the displacer's axial movement, maintaining regenerator material temperature stability throughout the refrigeration cycle
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 by stabilizing the temperature of the ceramic-based magnetic regenerator material, thereby maintaining consistent specific heat and improving the overall cryogenic performance of the cryocooler.
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 and that includes a stage end portion and a stage tubular portion connecting the stage end portion to the cylinder
Data Source
AI summary
A cryocooler includes a cylinder that has a first thermal conductivity and that extends in an axial direction, a cooling stage that has a second thermal conductivity higher than the first thermal conductivity and that includes a stage end portion and a stage tubular portion connecting the stage end portion to the cylinder in the axial direction, a displacer that is capable of reciprocating in the axial direction in the cylinder, that forms an expansion space with the stage end portion, and in which the expansion space takes a maximum volume at a top dead center, and a ceramic-based magnetic regenerator material that is accommodated in the displacer and of which an axial position in the displacer is determined to overlap the stage tubular portion in the axial direction when the displacer is at the top dead center.