Refrigeration and/or liquefaction device using selective pre-cooling, and corresponding method
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Solution Overview
Problem
Existing refrigeration and liquefaction devices for helium are ill-suited for both normal operation and cooling-down phases due to constraints on temperature differences and performance, requiring inefficient use of liquid nitrogen and varying heat exchanger technologies.
Innovation Solution
A device with a working gas loop circuit incorporating a compression station, cold box with series and parallel heat exchangers, and a pre-cooling system using auxiliary cryogenic fluid to manage temperature differences and optimize heat exchange during both phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid nitrogen pre-cooling is used during cooling-down phase, then negative calories are supplied to cool the working gas, but the temperature difference between nitrogen and helium streams becomes greater than 50K which reduces heat exchange efficiency
Solution Approach 1:
The heat exchanger is divided into multiple sections with different heat exchange mechanisms. The first section uses a main exchanger for high-performance heat exchange when temperature differences are small, while the second section uses a secondary exchanger specifically designed to handle large temperature differences during pre-cooling, allowing each section to operate in its optimal range
Solution Approach 2:
Different sections of the heat exchanger system are assigned different functional qualities based on local operating conditions. The main exchanger section is optimized for normal operation with small temperature differences, while the secondary exchanger section is optimized for pre-cooling with large temperature differences, ensuring each local region operates with appropriate heat exchange characteristics
2Loss of energy
If the device is optimized for normal operation with small temperature differences, then heat exchange performance is high, but it becomes ill-suited for cooling-down phase with large temperature differences
Solution Approach 1:
The heat exchanger system is designed with multi-functionality to handle both normal operation and cooling-down phase effectively. By incorporating both a main exchanger and a secondary exchanger with different characteristics, the system can adapt to different operational requirements, serving multiple functions across different operating conditions
Solution Approach 2:
The system dynamically switches between different heat exchanger configurations based on operational phase. During normal operation, the main exchanger handles the heat exchange with optimized performance. During cooling-down phase, the system activates the secondary exchanger to handle large temperature differences, creating a dynamic adaptation to changing operational conditions
3Temperature
If the device is optimized for cooling-down phase with large temperature differences, then pre-cooling capability is improved, but pressure drop becomes excessively high when helium temperatures are still high
Solution Approach 1:
The cooling process is segmented into different stages handled by different exchangers. The secondary exchanger handles the initial pre-cooling stage with large temperature differences, while the main exchanger takes over for subsequent stages, distributing the thermal load and preventing excessive pressure drop in any single component
Solution Approach 2:
The secondary exchanger acts as an intermediary component that facilitates the transition from ambient temperature to cryogenic temperatures. It mediates the heat exchange process during pre-cooling, allowing the main exchanger to operate within its optimal pressure and temperature difference ranges, thereby preventing excessive pressure drop
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 enables efficient cooling of heavy components from ambient to 80K with reduced liquid nitrogen consumption and compact exchanger design, maintaining performance across all operational modes.
Implementation Method 1
a pre-cooling system comprising a volume of auxiliary cryogenic fluid such as liquid nitrogen, the volume being connected to the working circuit via at least one heat exchanger in order selectively to transfer negative calories from the auxiliary fluid to the working gas
Implementation Method 2
a cold box for cooling the working gas and comprising a plurality of heat exchangers arranged in series
Implementation Method 3
at least one member for expanding the working gas
Data Source
AI summary
Refrigeration device comprising a working circuit in a loop for the working gas and comprising, in series: a compression station, a cold box, a system for the exchange of heat between the cooled working gas and a point of use, a system for the additional pre-cooling of the working gas leaving the compression station comprising an auxiliary cryogenic fluid volume, the cold box comprising a first cooling stage for the working gas comprising a first and a second heat exchanger, these being connected both in series and in parallel to the working circuit at the outlet of the compression station, the first cooling stage also comprising a third heat exchanger selectively exchanging heat with the auxiliary fluid, characterized in that the third heat exchanger is connected both in series and in parallel to the first and to the second heat exchangers, the working circuit comprising a recuperation pipe fitted with at least one valve and which connects the outlet of the third heat exchanger to the second heat exchanger.