Series Cryogenic Cold Box With Welded Intermediate Heat Exchanger
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Solution Overview
Problem
Cryogenic installations face challenges in maintaining high-performance cooling across both transient and steady states due to mechanical limitations of brazed aluminum heat exchangers under steep thermal gradients, leading to uneven performance and complexity in design and operation.
Innovation Solution
A refrigeration method using a working gas like helium, which circulates through a cold box comprising a brazed plate and fin aluminum heat exchanger, a welded-plate intermediate exchanger made of stainless steel, and another brazed plate and fin aluminum heat exchanger, where a significant portion of the gas stream passes through the intermediate exchanger to absorb most of the temperature difference, thereby protecting the more fragile exchangers and optimizing thermal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If brazed aluminum heat exchangers are used to optimize thermal efficiency and limit pressure drops in steady state, then thermal performance is improved, but the exchangers cannot withstand steep thermal gradients during transient cooling
Solution Approach 1:
The patent introduces a robust intermediate heat exchanger as a mediator between the brazed aluminum exchangers and the hot working gas during transient cooling. This intermediate exchanger absorbs the thermal shock and protects the fragile aluminum exchangers from steep thermal gradients, while still enabling efficient heat transfer through the series configuration.
2Reliability
If auxiliary cooling systems with liquid nitrogen baths and complex switchover circuits are added to protect aluminum exchangers during transient state, then protection during cooling is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the protective function with the existing heat exchanger train by adding a robust intermediate exchanger in series with the aluminum exchangers. This integration eliminates the need for separate auxiliary cooling systems and complex switchover circuits, as the intermediate exchanger provides continuous protection during both transient and steady-state operation.
3Reliability
If the working gas temperature is reduced by at least 100 K in the intermediate exchanger, then the thermal load on aluminum exchangers is reduced, but the intermediate exchanger must handle significant temperature difference
Solution Approach 1:
The patent changes the material parameter of the intermediate exchanger to use robust materials (such as stainless steel) that can withstand steep thermal gradients. This material selection enables the exchanger to handle the significant temperature difference (at least 100 K) between the hot working gas and the cold aluminum exchangers, while providing mechanical strength and thermal shock resistance.
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 allows for effective cooling across a wide temperature range, improving the longevity and performance of the heat exchangers, reducing the size of the cold box, and enabling simple, compact, and multifunctional operation of cryogenic installations.
Implementation Method 1
the working gas is cooled by making said working gas circulate through a cold box which comprises in series at least a first brazed plate and fin aluminum heat exchanger, a second welded-plate heat exchanger and a third brazed plate and fin aluminum heat exchanger
Implementation Method 2
the second exchanger is able without damage to withstand steep temperature gradients, it can by itself perform a high-amplitude cooling of the working gas
Data Source
AI summary
Embodiments of the present invention relate to a refrigeration method, during which a user is supplied with frigories by means of a working gas, such as helium, that is cooled by having the same flow into a cold box that comprises, in series, at least one first aluminum heat exchanger having brazed plates and flanges, one second heat exchanger having welded plates, and one third aluminum heat exchanger having brazed plates and flanges in such a way that the flow of said working gas is at least partially caused to pass, consecutively, through the first exchanger, then through the second exchanger, and finally through the third exchanger before said working gas flow is directed to the user in order to supply the user with frigories.