Method for suppressing the blockage of miniature Joule-Thomson cryocooler based on photothermal effect

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Solution Overview

Problem

Miniature Joule-Thomson cryocoolers face blockage issues due to trace water impurities, which condense and deposit in the throttle, leading to performance degradation and limited continuous operation, as existing solutions like heating the whole cold end are not suitable for continuous low-temperature operation.

Innovation Solution

A method utilizing the photothermal effect by selectively heating ice in the throttle with electromagnetic waves of specific wavelengths, based on the material's absorptivity, to remove ice without heating the entire cold end, maintaining continuous low-temperature operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the whole cold end of the cryocooler is heated to sublimate and remove ice, then the blockage is removed and the channel size is restored, but the continuous low-temperature operation requirement cannot be met

Engineering Contradiction:

Improveblockage removalVSAvoidcold end temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent applies local quality by using electromagnetic radiation to heat only the ice deposits in the throttle region, while the rest of the cold end remains at low temperature. The electromagnetic radiation source is positioned to target specifically the throttle area where ice blockage occurs, creating a localized heating zone that sublimates ice without raising the temperature of the entire cold end structure.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent replaces the conventional thermal conduction heating method with electromagnetic radiation heating. Instead of using thermal conduction from a heater that would heat the entire cold end, the system uses electromagnetic waves (infrared or microwave) that can penetrate and selectively heat the ice deposits through the throttle region, achieving blockage removal without mechanical contact or widespread thermal conduction.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Quantity of substance

If trace water in the working medium is removed by a filter, then most water is eliminated, but trace water at ppb-ppm level remains and causes blockage

Engineering Contradiction:

Improvewater content reductionVSAvoidblockage prevention

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent converts the harmful effect of trace water deposition into a beneficial process by using the same trace water's absorption characteristics of electromagnetic radiation. The trace water molecules in the ice deposits absorb electromagnetic radiation energy and convert it to thermal energy, causing sublimation. Thus, the previously harmful trace impurities become the target of selective heating and removal.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach effectively suppresses blockage by selectively removing ice in the throttle using targeted electromagnetic waves, ensuring continuous operation and improved performance of miniature Joule-Thomson cryocoolers.

Implementation Method 1

by taking advantage of the difference between the material (such as glass, silicon, etc.) of the miniature Joule-Thomson cryocooler and the ice in the absorptivity to electromagnetic waves in near/mid-infrared bands, the ice in the throttle can be heated and removed via a photothermal effect of electromagnetic waves of specific wavelengths in this band

Methodology Applied

Scientific EffectPhotothermal effect: Absorption (EM radiation)

Implementation Method 2

the ice in the throttle can be heated and removed via a photothermal effect of electromagnetic waves of specific wavelengths

Methodology Applied

Scientific EffectAbsorption of electromagnetic radiation: Absorption (EM radiation)

Data Source

PatentUS11561035B2Method for suppressing the blockage of miniature Joule-Thomson cryocooler based on photothermal effect

Publication Date: 2023.01.24 TSINGHUA UNIVERSITY

AI summary

A method for suppressing the blockage of a miniature Joule-Thomson cryocooler based on a photothermal effect includes: determining form and temperature of a trace impurity contained in a working medium of the cryocooler according to an operating condition of the cryocooler, and selecting an optimal wavelength of an electromagnetic wave based on the form and temperature of the impurity and a peak of absorption spectrum of the impurity to electromagnetic waves; estimating, via a prediction model of input power of the electromagnetic wave, an initial value of input power corresponding to the optimal wavelength; and emitting an electromagnetic wave with the power W by a laser capable of generating the optimal wavelength in a direction perpendicular to a passage of a throttle in the cryocooler to eliminate the impurity in the passage of the throttle.