Cooling device
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Solution Overview
Problem
Existing cooling devices for detectors in Dewar vessels have a large time constant for temperature control, limiting temperature stability and allowing operation only 5°K above the boiling temperature of the pressurized gas, with cooling power directly affecting temperature.
Innovation Solution
A cooling device with a Joule-Thomson cooler and an expansion nozzle, featuring a first temperature sensor in the expansion chamber and a second temperature sensor outside, uses a control device to record a temperature gradient and adjust the final control element, allowing operation in the liquid phase for improved stability and regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the temperature sensor is disposed on the detector element in the jacket cavity of the Dewar vessel, then the detector temperature can be directly monitored, but the time constant for temperature control becomes large, limiting temperature stability
Solution Approach 1:
The patent introduces an intermediary temperature sensor in the expansion chamber that indirectly monitors the cooling state through the temperature gradient, rather than directly sensing the detector temperature. This intermediary measurement point responds faster to cooling changes while still providing accurate control information to the control device, which adjusts the final control element accordingly.
Solution Approach 2:
The patent measures the temperature gradient in the expansion chamber as a preliminary indicator of cooling state, before the full effect propagates to the detector element. This preliminary measurement allows the control system to anticipate and adjust cooling power earlier, reducing the overall time constant and improving temperature stability.
2Reliability
If actively regulated cooling devices operate above the boiling temperature of the pressurized gas, then stable operation is achieved, but the achievable low temperature is limited to approx. 5°K above the boiling temperature
Solution Approach 1:
The patent implements a feedback control system where the temperature sensor in the expansion chamber continuously monitors the cooling state and feeds this information back to the control device. The control device adjusts the final control element based on this feedback, enabling stable operation even when the temperature approaches or reaches the boiling point of the pressurized gas, thereby breaking the 5°K limitation.
Solution Approach 2:
The patent changes the control parameter from direct detector temperature to the temperature gradient in the expansion chamber. This parameter change allows the system to operate at lower temperatures closer to the boiling point, as the feedback control maintains stability by continuously adjusting the cooling power based on the gradient measurement rather than relying on a fixed temperature margin.
3Productivity
If a temperature sensor is disposed in the expansion chamber to monitor cooling power, then the time constant is reduced, but the sensor must operate in a harsh environment with mixed gas and liquid phases
Solution Approach 1:
The temperature sensor in the expansion chamber serves as an intermediary measurement point that captures the cooling state without being directly exposed to the detector element's harsh environment. By positioning the sensor in the expansion chamber where it measures the temperature gradient of the cooling medium, it achieves fast response while avoiding direct contact with potential contaminants or extreme conditions at the detector interface.
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 reduces the time constant of the control loop, enabling operation at the boiling temperature with high temperature stability by exploiting the inherent temperature stability of the liquid phase, and allows for precise control of the mixing ratio of gas and liquid phases.
Implementation Method 1
A pressurized gas or general coolant that is fed in is expanded at the expansion nozzle and as a result cools according to its Joule-Thomson thermal coefficients into a region close to its boiling temperature
Implementation Method 2
a first temperature sensor is disposed in the expansion chamber and a second temperature sensor is disposed within the Dewar vessel outside of the expansion chamber
Implementation Method 3
a control device is provided that is configured for recording a temperature gradient from the sensor values of the first temperature sensor and of the second temperature sensor and for adjustment of the final control element depending on the recorded temperature gradient
Data Source
Figure 1
AI summary
A cooling device (1) is specified for cooling a detector element (3) disposed in the jacket cavity (4) of a Dewar vessel (4) by means of a Joule-Thomson cooler (2) with an expansion nozzle (15) that opens into an expansion chamber (16), wherein the cooling device comprises a final control element (22) that is adjustable depending on the temperature for influencing the flow through the expansion nozzle (15). It is provided here that a first temperature sensor (34) is disposed in the expansion chamber (16) and a second temperature sensor (35) is disposed within the Dewar vessel (4) outside the expansion chamber (16), and that the cooling device comprises a control device (40) that is configured for detecting a temperature gradient from the sensor values of the first temperature sensor (34) and of the second temperature sensor (35) and for adjusting the final control element (22) depending on the detected temperature gradient.