Cryogenic cooling system
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Solution Overview
Problem
Mechanical cryo-coolers require longer cool-down times for target assemblies with high thermal mass due to the limited cooling power of their second stage, and existing solutions involving liquid cryogens are bulky, expensive, and scarce.
Innovation Solution
A cryogenic cooling system combining a mechanical refrigerator with a heat pipe and a heat switch assembly, allowing for efficient thermal communication between the second cooled stage and the target assembly through a heat pipe cooling mode and gas gap cooling mode, reducing the need for moving parts and enhancing cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If liquid cryogens are used for cooling target assemblies, then cooling speed is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical system of liquid cryogen handling (tanks, pumps, transfer lines) with a solid-state cooling system using a mechanical refrigerator coupled to the target assembly, eliminating the need for bulky liquid handling apparatus while maintaining effective cooling
Solution Approach 2:
The patent extracts the cooling function from the liquid cryogen system and implements it through a dedicated mechanical refrigerator unit that is directly coupled to the target assembly, separating the cooling generation from the target cooling process
2Power
If liquid cryogens are used for cooling target assemblies, then cooling power is improved, but availability and cost worsen
Solution Approach 1:
The patent substitutes mechanical refrigeration systems for liquid cryogen-based cooling, using a mechanical refrigerator with evaporative cooling to provide the necessary cooling power without depleting scarce helium resources
Solution Approach 2:
The patent changes the cooling mechanism from chemical/physical properties of liquid cryogens to mechanical refrigeration cycles, utilizing phase change of a working fluid in a controlled mechanical system to provide sustained cooling power
3Device complexity
If mechanical refrigerators are used for cooling target assemblies, then device complexity is reduced, but cooling speed worsens
Solution Approach 1:
The patent employs periodic evaporation and condensation cycles of the working fluid in the heat pipe to accelerate heat transfer from the target assembly to the mechanical refrigerator, significantly increasing the effective cooling speed compared to steady-state conduction alone
Solution Approach 2:
The patent utilizes phase transitions (evaporation and condensation) of the working fluid in the heat pipe to enhance heat transfer efficiency, allowing rapid removal of heat from the target assembly and significantly reducing cool-down time despite the simplicity of the mechanical refrigerator
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 combination significantly reduces the cool-down time for target assemblies by leveraging the high conductance of heat pipes and the operational range of gas gap heat switches, achieving faster cooling from room temperature to cryogenic temperatures while minimizing the use of liquid cryogens and avoiding unwanted heat generation.
Implementation Method 1
the temperature of the second cooled stage causes the coolant in the first part of the heat pipe to condense
Implementation Method 2
the temperature of the target assembly causes the coolant within the second part of the heat pipe to be gaseous
Implementation Method 3
the target assembly is cooled by the movement of the condensed liquid coolant from the first part of the heat pipe to the second part of the heat pipe
Implementation Method 4
the heat switch assembly comprising one or more gas gap heat switches
Implementation Method 5
a mechanical refrigerator having a first cooled stage and a second cooled stage, the second cooled stage being configured to reach a lower base temperature than the first cooled stage
Data Source
AI summary
A cryogenic cooling system is provided comprising: a mechanical refrigerator, a heat pipe and a heat switch assembly. The mechanical refrigerator has a first cooled stage and a second cooled stage. The heat pipe has a first part coupled thermally to the second cooled stage and a second part coupled thermally to a target assembly. The heat pipe is adapted to contain a condensable gaseous coolant when in use. The heat switch assembly comprises one or more gas gap heat switches, a first end coupled thermally to the second cooled stage and a second end coupled thermally to the target assembly. The cryogenic cooling system is adapted to be operated in a heat pipe cooling mode in which the temperature of the second cooled stage is lower than the first cooled stage and wherein the temperature of the target assembly causes the coolant within the second part of the heat pipe to be gaseous and the temperature of the second cooled stage causes the coolant in the first part of the heat pipe to condense. The target assembly is cooled by the movement of the condensed liquid coolant from the first part of the heat pipe to the second part of the heat pipe during the heat pipe cooling mode. The cryogenic cooling system is further adapted to be operated in a gas gap cooling mode in which the temperature of the second cooled stage causes freezing of the coolant. The heat switch assembly is adapted to provide cooling from the second cooled stage to the target assembly during the gas gap cooling mode via the one or more gas gap heat switches.