Cryogenic Displacer Groove Layout for Seal-Free Cooling Efficiency
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Solution Overview
Problem
Cryogenic refrigerators with displacers face reduced cooling efficiency due to direct gas flow between room temperature and expansion spaces, which is exacerbated by the degradation of sealing mechanisms like O-rings, leading to suboptimal refrigeration performance.
Innovation Solution
A cryogenic refrigerator design featuring a displacer with a helical groove on its periphery, creating a gap between the displacer and cylinder, where the volume ratio of the groove to the gap is optimized between 8 and 75, allowing for improved heat exchange and reduced heat loss without a sealing mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a sealing mechanism like an O-ring is provided to prevent refrigerant gas flow in the gap between cylinder and displacer, then cooling efficiency is improved, but the sealing mechanism degrades over time reducing sealability and refrigeration capacity
Solution Approach 1:
The invention removes the sealing mechanism (O-ring) from the system entirely. Instead of trying to seal the gap between the displacer and cylinder, the design accepts the gap's existence and uses a depressed part on the displacer to control refrigerant gas flow, eliminating the reliability issues associated with sealing mechanism degradation
Solution Approach 2:
The invention converts the potentially harmful direct gas flow through the gap into a beneficial controlled flow path. The depressed part on the displacer creates a specific flow pattern where refrigerant gas flows through the gap and then through the depressed part, utilizing the gap rather than fighting against it, thereby maintaining cooling efficiency without requiring seals
2Device complexity
If no sealing mechanism is provided allowing direct gas flow through the gap, then device complexity is reduced, but cooling efficiency deteriorates due to absence of regenerator material cooling
Solution Approach 1:
The invention applies a localized depressed part on the displacer surface to control gas flow in a specific region. This local structural modification creates a controlled flow path that ensures refrigerant gas passes through the regenerator material in the depressed part, maintaining cooling efficiency without adding complex sealing mechanisms throughout the entire system
Solution Approach 2:
The depressed part acts as an intermediary structure that mediates the gas flow between the gap and the regenerator material. It guides the refrigerant gas to flow through the regenerator material located in the depressed part, ensuring heat exchange occurs even though the gap itself remains open and unsealed
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 enhances refrigeration performance by optimizing the volume ratio of the groove to the gap, improving heat exchange and maintaining high efficiency, particularly at low temperatures around 3.85 K, while minimizing heat loss and the need for sealing mechanisms.
Implementation Method 1
cold temperatures are produced in the expansion space by optimizing the timing between the reciprocation of the displacer and the supply and return process of the refrigerant gas
Implementation Method 2
the refrigerant gas cooled by the produced cold temperatures cools the regenerator material inside the displacer when the refrigerant gas is returned to the compressor through the displacer at the gas return process
Data Source
AI summary
A cryogenic refrigerator includes a cylinder, a displacer accommodated in the cylinder so as to reciprocate inside the cylinder with a gap formed between the periphery of the displacer and the interior surface of the cylinder, and a depressed part formed on at least one of the periphery of the displacer and the interior surface of the cylinder. The ratio of the volume of the depressed part to the volume of the gap satisfies a condition of 8≤Vd/Vg≤75, where Vd is the volume of the depressed part and Vg is the volume of the gap.