Process and apparatus for establishing vacuum insulation under cryogenic condition
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Solution Overview
Problem
Existing cryogenic processes face challenges in creating and maintaining vacuum insulation efficiently and cost-effectively, particularly at low temperatures, due to the need for costly and time-consuming vacuum pumping and the use of additional insulation materials.
Innovation Solution
A process involving purging cycles with a high-purity filling gas, such as carbon dioxide, to transform directly from gas to solid phase within the insulation enclosure, eliminating the need for hard vacuum pumping and reducing the use of insulation materials, while achieving a soft vacuum of around 100 Pa, which is sufficient for cryogenic applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If vacuum insulation is used for cryogenic equipment below -150°C, then heat transfer resistance is improved, but the cost and complexity of creating and maintaining hard vacuum increases significantly
Solution Approach 1:
The invention changes the operating parameters by using a filling gas that undergoes phase transition at cryogenic temperatures. The filling gas is introduced at ambient temperature and pressure, then transforms to solid phase when the equipment operates below -150°C, automatically providing insulation without requiring hard vacuum systems.
Solution Approach 2:
The filling gas acts as an intermediary substance between the cryogenic equipment and the ambient environment. It mediates the thermal interaction by transitioning from gas phase (allowing heat transfer) to solid phase (providing insulation), eliminating the need for complex vacuum systems.
2Loss of energy
If hard vacuum (below 5 Pa) is created at ambient temperature, then insulation performance is improved, but the time and cost required for vacuum creation increases significantly
Solution Approach 1:
The filling gas is introduced into the insulation enclosure before the cryogenic equipment operates. The gas is prepared at ambient conditions and distributed throughout the enclosure, so that when cooling occurs, the phase transition and insulation effect are already in place, eliminating the need for time-consuming hard vacuum creation.
Solution Approach 2:
Instead of creating hard vacuum at ambient temperature and maintaining it through operation, the invention introduces gas at ambient conditions and relies on the reverse process - phase transition to solid during operation - to achieve the insulation effect, inverting the conventional vacuum creation approach.
3Loss of energy
If additional insulation materials (perlite, mineral wool, aerogel) are used to maintain vacuum insulation, then insulation effectiveness is improved, but the cost and complexity of the system increases
Solution Approach 1:
The filling gas provides self-service insulation by automatically transitioning from gas to solid phase when the cryogenic equipment operates below -150°C. This self-transforming property eliminates the need for additional insulation materials or active maintenance systems, reducing complexity while maintaining effectiveness.
Solution Approach 2:
The invention exploits the phase transition of the filling gas from gas phase at ambient temperature to solid phase at cryogenic temperatures. This phase change provides automatic insulation adjustment based on operating conditions, replacing the need for static insulation materials like perlite or aerogel.
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 method significantly reduces the time and cost associated with vacuum creation, eliminates the need for expensive pumps, and maintains efficient insulation at cryogenic temperatures, thereby improving the efficiency of cryogenic equipment.
Implementation Method 1
the filling gas undergoes transformation from gas phase to solid phase without going through liquid phase during the cooling caused by operation of the cryogenic equipment
Implementation Method 2
operating the cryogenic equipment to cool the insulation enclosure and the filling gas to a temperature equal to or below that solidifies the filling gas
Data Source
AI summary
A process for establishing vacuum insulation under cryogenic condition and an apparatus compatible with such process are described. When an insulation enclosure filled with high purity CO2 is evacuated to around 100 absolute Pa at ambient temperature, hard vacuum of below 1 absolute Pa may be automatically obtained within the insulation enclosure when temperature drops to around or below −170° C. This process can be employed to provide vacuum insulation for cold box housing air separation units operated under cryogenic condition.