Cryogenic device with compact exchanger
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Solution Overview
Problem
Existing cold generation devices using the Joule-Thomson expansion principle face challenges in optimizing heat exchange efficiency while minimizing size and reducing axial conduction losses, as conventional counter-current exchangers with fins increase size and reduce efficiency.
Innovation Solution
A cold generation device employing a stack of sintered porous pellets with interposed thermal insulating grids and a capillary within the pellets, eliminating the need for fins and reducing axial conduction, thereby enhancing heat exchange efficiency and compactness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If radial fins are provided on the capillary to increase heat exchange surface, then heat exchange efficiency is improved, but the spacing between consecutive turns increases and the number of turns decreases, partially neutralizing the optimization
Solution Approach 1:
The patent replaces the conventional capillary with a porous sintered structure. The porous material provides an extremely large internal surface area for heat exchange without requiring external fins. The fluid flows through the porous matrix, maximizing contact area while maintaining compact dimensions and avoiding the spacing issues introduced by fins.
Solution Approach 2:
The invention uses a composite structure combining sintered porous material with the capillary assembly. This composite approach integrates the heat exchange function directly into the structural component, eliminating the need for separate fins and achieving both high surface area and high turn density.
2Area of stationary object
If the length of the capillary exchanger is increased to optimize heat exchange, then heat exchange efficiency is improved, but the size of the exchanger and cold machine increases
Solution Approach 1:
The porous sintered structure provides an extremely high surface area to volume ratio. The internal porosity creates numerous flow paths and heat exchange surfaces within a compact external dimension, allowing extensive heat exchange surface area without increasing the overall exchanger length or volume.
Solution Approach 2:
The invention transitions from a one-dimensional heat exchange approach (long capillary) to a three-dimensional heat exchange approach (porous matrix). The fluid flows through the volumetric porous structure, utilizing all three dimensions for heat exchange, thereby achieving high surface area within a compact volume.
3Strength
If a mandrel is used to support the capillary, then structural support is provided, but axial conduction occurs which causes heat loss and reduces efficiency
Solution Approach 1:
The invention removes the mandrel component entirely from the design. The capillary is supported directly by the porous structure or by alternative non-conductive means, eliminating the source of axial conduction losses. This extraction of the problematic component directly addresses the energy loss issue.
Solution Approach 2:
The porous structure serves as an intermediary that provides structural support without creating thermal conduction paths. The distributed porous matrix supports the capillary while minimizing thermal contact, acting as a thermal isolator rather than a conductor.
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 solution significantly increases heat exchange surface area, reducing cooling time and allowing for a compact design without increasing size, while maintaining performance, by utilizing sintered pellets and capillary materials like silver or copper, and thermally insulating spacers to minimize thermal bridges.
Implementation Method 1
the heat exchanger consists of the stack of pellets made of porous material, and in particular sintered, constituting a cylindrical mandrel, in contact with which is wound a capillary within which circulates the high pressure fluid, the low pressure fluid pressure circulating against the current inside the porous mandrel thus formed
Implementation Method 2
between each of the pellets made of sintered material, a porous thermal insulating fabric, typically made of fiberglass, is interposed
Implementation Method 3
devices of the type in question implementing, as a source of cold, the principle of expansion known as 'Joule-Thomson'
Data Source
Figure 1~3
Figure 4~5
AI summary
The invention relates to a cold-generating device that uses the "Joule-Thomson" expansion principle. It comprises a heat exchanger inside which a high-pressure and a low-pressure fluid circulate in countercurrent. The heat exchanger consists of a stack of pellets (5) made of a porous material, particularly sintered material, forming a cylindrical mandrel at the periphery of which, and in contact with which, a capillary (10) is wound inside which the high-pressure fluid circulates, wherein the low-pressure fluid circulates in countercurrent inside the porous mandrel formed in this way.