Cryogenic Cold Finger Annulus Obstruction for Faster Cool-Down

Solution Overview

Problem

Cryogenic cooling systems face increased cool down time and reduced effectiveness due to convective currents formed between the cold finger and the Dewar, which hinder heat transfer and increase power requirements.

Innovation Solution

Inhibiting the formation of convective currents by inserting obstructions, such as thin disks, within the annulus between the cold finger and the Dewar to disrupt the convective loop, thereby enhancing heat transfer efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If the cold finger is inserted into the Dewar to cool the infrared detector, then the detector can be cooled to liquid nitrogen temperatures, but convective currents form in the annulus between the cold finger and Dewar, increasing cool down time and power requirements

Engineering Contradiction:

Improvedetector temperatureVSAvoidcool down time

Core Design Contradiction:

TemperatureVSLoss of time

Solution Approach 1:

The patent introduces an intermediary substance (such as a thermal conductor or heat transfer medium) in the annulus between the cold finger and Dewar to replace the convective air currents. This intermediary substance conducts heat more efficiently without creating harmful convection loops, thereby reducing cool down time while maintaining the detector at the required temperature.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If the cold finger is inserted into the Dewar to cool the infrared detector, then the detector can be cooled to liquid nitrogen temperatures, but convective currents form in the annulus between the cold finger and Dewar, increasing power requirements

Engineering Contradiction:

Improvedetector temperatureVSAvoidpower requirements

Core Design Contradiction:

TemperatureVSUse of energy by moving object

Solution Approach 1:

The patent introduces an intermediary substance (such as a thermal conductor or heat transfer medium) in the annulus between the cold finger and Dewar to replace the convective air currents. This intermediary substance conducts heat more efficiently without creating harmful convection loops, thereby reducing cool down time while maintaining the detector at the required temperature.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If the annulus between the cold finger and Dewar is left open, then the structure is simple, but convective currents transfer hot and cold air, reducing heat transfer efficiency

Engineering Contradiction:

Improvestructure complexityVSAvoidheat transfer efficiency

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent introduces an intermediary substance (such as a thermal conductor or heat transfer medium) in the annulus between the cold finger and Dewar to replace the convective air currents. This intermediary substance conducts heat more efficiently without creating harmful convection loops, thereby reducing cool down time while maintaining the detector at the required temperature.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 reduces cool down time and increases the lifespan of the cooling system by minimizing cooling requirements, as it prevents the undesirable transfer of hot and cold air, allowing for more efficient temperature maintenance.

Implementation Method 1

Joule-Thomson and Stirling Cycle coolers are the two cooling techniques most often used to provide controlled cooling at such extreme temperatures

Methodology Applied

Scientific EffectJoule-Thomson effect: Joule-Thomson Effect

Implementation Method 2

Joule-Thomson and Stirling Cycle coolers are the two cooling techniques most often used to provide controlled cooling at such extreme temperatures

Methodology Applied

Scientific EffectStirling cycle: Stirling Cycle

Implementation Method 3

a cold finger operable to receive the cooling fluid

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 4

inhibiting the formation of convective currents within the annulus in a direction between the first end and the second end

Methodology Applied

Scientific EffectConvection: Convection

Data Source

PatentUS7415830B2Method and system for cryogenic cooling

Publication Date: 2008.08.26 RAYTHEON CO

AI summary

According to one embodiment, a method for improving heat transfer between a cold finger of a cryogenic cooler and a Dewar includes forming an annulus between the cold finger of the cryogenic cooler and the Dewar by inserting the cold finger into the Dewar. The cold finger has a first end and a second end. The method also includes inhibiting the formation of convective currents within the annulus in a direction between the first end and the second end. According to another embodiment of the invention, the cooling system includes a cryogenic cooler that includes a cooling section operable to generate cooling fluid and a cold finger operable to receive the cooling fluid. The cooling system also includes a Dewar formed with a void region coupled to an infrared detector. The cold finger is positioned within the void region of the Dewar creating an annulus. The cooling system also includes at least one obstruction disposed within the annulus and operable to inhibit the formation of convective currents in a direction along a length of the cold finger.