Cryocooler Regenerator With Anisotropic Carbon Layers for Axial Heat Isolation
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Solution Overview
Problem
Cryocoolers face reduced cooling capacity and effectiveness due to heat flow between the warm and cold ends, as conventional regenerators often have high end-to-end thermal conduction, which is not adequately addressed by using materials with low thermal conductivities.
Innovation Solution
Incorporating carbon-based anisotropic thermal layers, such as carbon nanotubes or graphene, into the regenerator to reduce axial heat flow and enhance radial or lateral heat spreading, thereby reducing thermal conductivity along the regenerator while maintaining efficient heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If materials with low thermal conductivities are used in the regenerator, then axial heat flow is reduced, but volumetric heat capacity becomes inadequate
Solution Approach 1:
The regenerator is designed with spatially varying thermal properties: the porous matrix material provides low axial thermal conductivity for heat isolation, while the carbon-based anisotropic layers embedded within provide high radial thermal conductivity for lateral heat spreading. This local differentiation of thermal properties allows the system to simultaneously reduce axial heat flow and maintain adequate volumetric heat capacity through the combined effect of different materials in different spatial orientations.
Solution Approach 2:
The regenerator employs a composite structure combining a porous matrix material (such as sintered metal or ceramic) with carbon-based anisotropic layers (such as carbon nanotubes or graphene). The porous matrix provides the necessary volumetric heat capacity and structural framework, while the carbon-based layers contribute anisotropic thermal conductivity properties. This composite material approach resolves the contradiction by integrating materials with complementary thermal properties to achieve both low axial conduction and sufficient heat storage capacity.
2Productivity
If conventional regenerator materials are used, then structural integrity is maintained, but cooling capacity and effectiveness are reduced due to high end-to-end thermal conduction
Solution Approach 1:
The regenerator implements directional thermal property differentiation through carbon-based anisotropic layers that exhibit high thermal conductivity in the radial direction (perpendicular to the axial flow direction) and low thermal conductivity in the axial direction. This local quality variation allows heat to be effectively spread laterally across the regenerator cross-section while preventing axial heat leakage from the cold end to the warm end, thereby improving cooling capacity without sacrificing structural integrity.
Solution Approach 2:
The invention introduces a dimensional approach to thermal management by utilizing the anisotropic thermal conductivity of carbon-based materials to preferentially conduct heat in the radial dimension while blocking axial heat flow. This dimensional selectivity in heat transfer pathways allows the regenerator to maintain structural integrity along the axial dimension while achieving superior thermal isolation in that same dimension through the directional properties of the carbon-based layers.
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 configuration improves the efficiency of cryocoolers by reducing axial heat transfer and increasing thermal spreading, potentially enhancing cooling capacity and efficiency by 16%-37% depending on the volume of carbon nanotubes used, while maintaining low volumetric heat capacity and structural integrity.
Implementation Method 1
The anisotropic thermal layer is configured to reduce a flow of heat axially along the regenerator and to spread the absorbed heat radially or laterally in a plane of the anisotropic thermal layer
Implementation Method 2
The anisotropic thermal layer includes at least one allotropic form of carbon
Data Source
AI summary
An apparatus includes a regenerator configured to transfer heat to a fluid and to absorb heat from the fluid as the fluid flows between a warm end and a cold end of a cryocooler. The regenerator includes an anisotropic thermal layer configured to reduce a flow of heat axially along the regenerator and to spread the absorbed heat radially or laterally in a plane of the anisotropic thermal layer. The anisotropic thermal layer includes at least one allotropic form of carbon. The anisotropic thermal layer could have a higher radial or lateral thermal conductivity and a lower axial thermal conductivity. The anisotropic thermal layer could include carbon nanotubes and/or graphene. The regenerator could include multiple anisotropic thermal layers that divide the regenerator into multiple segments, where the anisotropic thermal layers are configured to reduce heat transfer between adjacent segments of the regenerator.