Cryocooler Intermediate Temperature Control for Cool-Down
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Solution Overview
Problem
The cool-down time of cryocoolers is prolonged due to uneven cooling rates between the first and second cooling stages, particularly when cooling objects with different heat capacities, leading to increased time requirements.
Innovation Solution
A cryocooler with a heater thermally coupled to the first cooling stage, controlled by a controller to maintain an intermediate target temperature between the initial and final temperatures, balancing the cooling rates of both stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the cryocooler operates without intermediate temperature control, then the cooling process is simpler, but the cool-down time is prolonged due to uneven cooling rates between stages
Solution Approach 1:
The controller receives temperature information from both the first and second cooling stages, compares the first stage temperature to the intermediate target temperature, and adjusts the heater output accordingly. This feedback control mechanism enables dynamic adjustment of the cooling process to maintain balanced temperature reduction across stages, significantly reducing cool-down time while managing system complexity through intelligent control algorithms
Solution Approach 2:
The system dynamically changes the heater power parameter based on real-time temperature measurements. By adjusting the heater output power as a controllable parameter in response to temperature feedback, the system optimizes the cooling rate of the first stage to match the second stage, resolving the uneven cooling issue without requiring major structural modifications
2Speed
If the first cooling stage is cooled rapidly without control, then the cooling speed increases, but the cooling becomes unbalanced with the second stage, prolonging overall cool-down time
Solution Approach 1:
The heater applied to the first cooling stage provides a preliminary counteracting heat input that prevents excessive cooling. By anticipating the temperature differential that would naturally occur between stages, the system applies preemptive heating to the faster-cooling first stage, maintaining temperature balance and synchronized cooling progression throughout the cool-down process
Solution Approach 2:
The heater acts as an intermediary element between the cooling mechanism and the first cooling stage. This intermediary component modulates the thermal interaction by providing controlled heating that mediates the cooling rate, ensuring the first stage cools at a rate compatible with the second stage rather than cooling too rapidly on its own
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 method shortens the cool-down time by preventing excessive cooling of the first stage, ensuring balanced cooling rates and efficient distribution of working gas, thereby reducing the overall cool-down duration.
Implementation Method 1
a heater thermally coupled to the first cooling stage
Implementation Method 2
a cold head including a first cooling stage and a second cooling stage cooled to a lower temperature than the first cooling stage
Data Source
Figure 1
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AI summary
A cryocooler (10) includes: a cold head (14) including a first cooling stage (33) and a second cooling stage (35) cooled to a lower temperature than the first cooling stage (33); a heater (46) thermally coupled to the first cooling stage (33); a first temperature sensor (48a) that measures a first temperature of the first cooling stage (33); and a controller (50) configured to, during a cool-down operation of the cold head (14), acquire a first temperature of the first cooling stage (33) from the first temperature sensor (48a), and control the heater (46) to cause the first temperature of the first cooling stage (33) to follow an intermediate target temperature which is lower than an initial temperature of the cool-down operation and higher than a final target temperature of the first cooling stage (33).