Multi-Stage Joule-Thomson Cryocooler for Liquid Helium Temperatures
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Solution Overview
Problem
Current miniature Joule-Thomson cryocoolers face challenges in achieving liquid helium temperatures due to the low maximum Joule-Thomson transition temperature of helium, requiring additional precooling stages and suitable working fluids, which complicates the design and efficiency.
Innovation Solution
A miniature Joule-Thomson cryocooler with an integral structure formed by welding multiple base plates, where each stage uses a specific working fluid for precooling, with the first-stage working fluid achieving cooling without precooling, and subsequent stages using neon or hydrogen and helium, respectively, to achieve liquid helium temperatures through sequential precooling and heat exchange processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If helium is used as the working fluid in a Joule-Thomson cryocooler, then the cooling temperature can reach liquid helium temperatures, but the maximum Joule-Thomson transition temperature of helium is only 45 K, requiring additional precooling stages
Solution Approach 1:
The cryocooler is divided into multiple cooling stages, with each stage using a different working fluid optimized for its temperature range. The first stage uses nitrogen (max JT temperature 126 K) for initial cooling, the second stage uses neon (max JT temperature 250 K) for intermediate cooling, and the third stage uses helium (max JT temperature 45 K) for final liquid helium temperature achievement. This segmentation allows each stage to operate within its optimal temperature range, eliminating the need for excessive precooling stages.
Solution Approach 2:
The patent changes the working fluid parameters at different stages of the cooling process. By selecting working fluids with different maximum Joule-Thomson transition temperatures (nitrogen: 126 K, neon: 250 K, helium: 45 K), the system optimizes the cooling efficiency at each temperature level, allowing direct achievement of liquid helium temperatures without requiring additional precooling stages beyond the three main stages.
2Temperature
If multiple precooling stages are added to achieve liquid helium temperatures, then the cooling temperature can reach liquid helium range, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent merges multiple cooling stages into a single integrated cryocooler device with a unified structure. The three cooling stages (nitrogen, neon, helium) are combined in one device with shared components such as the common housing, integrated heat exchangers, and coordinated throttle valves. This merging approach reduces manufacturing complexity compared to assembling multiple separate cooling devices, while still achieving liquid helium temperatures through the sequential action of different working fluids.
3Volume of moving object
If a miniature cryocooler is designed for small electronic devices, then the size is reduced, but the cooling capacity becomes insufficient for maintaining cryogenic temperatures
Solution Approach 1:
The patent utilizes phase transitions of the working fluids (nitrogen, neon, and helium) to enhance cooling capacity in the miniature device. Each working fluid undergoes Joule-Thomson expansion and phase change at its respective stage, absorbing latent heat during the transition process. This phase transition mechanism allows the small cryocooler to achieve sufficient cooling capacity despite its compact size, as the phase changes provide intense cooling effects at each stage.
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 design allows for a compact, cost-effective, and high-precision cryocooler capable of reaching liquid helium temperatures with improved processing efficiency and reduced complexity, facilitating industrial mass production.
Implementation Method 1
a working fluid which may achieve the Joule-Thomson cooling effect without the precooling operation is referred to as a first-stage working fluid
Implementation Method 2
only neon and hydrogen are working fluids which may provide precooling temperatures below 45 K by a Joule-Thomson cooling operation
Implementation Method 3
the helium is referred to as a third-stage working fluid herein
Data Source
AI summary
A miniature Joule-Thomson cryocooler operating at liquid helium temperatures includes an integral structure formed by welding at least three base plates sequentially superposed, an outermost base plate in the at least three base plates is configured as a cover plate and configured to seal the rest of the at least three base plates, the rest of the at least three base plates is configured as a first-stage cooling circulator, a second-stage cooling circulator and a third-stage cooling circulator respectively, the first-stage cooling circulator, the second-stage cooling circulator and the third-stage cooling circulator have a first-stage working fluid, a second-stage working fluid and a third-stage working fluid respectively, the first-stage cooling circulator is configured to precool the second-stage working fluid and the third-stage working fluid through the first-stage working fluid, and the second-stage cooling circulator is configured to precool the third-stage working fluid through the second-stage working fluid.