Phase Change Medium Heat Exchanger for Laser Thermal Management

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Solution Overview

Problem

High average power solid state laser systems face challenges with bulky, heavy, and costly cooling systems that generate excessive flow vibrations, making them unsuitable for mobile platforms due to size and weight constraints, and requiring substantial electric power for pumps that produce high flow rates.

Innovation Solution

A thermal management system utilizing a phase change medium heat exchanger and pressurized gas to condition coolant between laser shots, allowing for efficient heat transfer and reduced coolant flow vibrations, with a smaller refrigerator for reconditioning the phase change medium, enabling a lightweight, compact, and low-cost cooling solution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If closed loop cooling systems are used to reject waste heat from SSL systems, then effective cooling is achieved, but the system becomes bulky and heavy

Engineering Contradiction:

Improvecooling effectivenessVSAvoidcooling system weight

Core Design Contradiction:

TemperatureVSWeight of stationary object

Solution Approach 1:

The patent utilizes phase change materials (PCM) that absorb heat from the laser crystal during phase transition (solid to liquid). The PCM is contained in a heat exchanger that directly contacts the laser crystal, absorbing waste heat during lasing operations and storing it as latent heat during phase change, thereby cooling the laser crystal without requiring bulky refrigeration systems.

Inventive Principle:

Principle #36Phase transitions

Solution Approach 2:

The patent extracts the refrigeration function from the cooling system by using passive phase change materials instead of active refrigeration cycles. The PCM-based heat exchanger is directly integrated with the laser crystal, removing the need for external coolants and complex closed-loop cooling infrastructure, significantly reducing system weight and volume.

Inventive Principle:

Principle #2Taking out (Extraction)

2Productivity

If high flow rates are used to support high energy SSL lasing, then effective cooling is achieved, but large electrically operated pumps are required

Engineering Contradiction:

Improvecooling capacityVSAvoidpump power consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The patent replaces the mechanical pump system with a passive thermal conduction and phase change mechanism. The PCM-based heat exchanger directly contacts the laser crystal and absorbs heat through thermal conduction and phase transition, eliminating the need for electrically operated pumps and their associated power consumption (20%-30% of the SSL system's electric power budget).

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If large pumps are used to achieve high flow rates, then cooling capacity is improved, but flow vibrations increase

Engineering Contradiction:

Improvecooling capacityVSAvoidflow vibration

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent eliminates the mechanical pump system that generates flow vibrations by using passive phase change materials. The PCM absorbs heat through phase transition and thermal conduction without requiring fluid flow, completely eliminating the wide band spectrum vibrations and resonances that perturb laser component alignment.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Temperature

If conventional cooling systems are used, then heat rejection is achieved, but the system becomes costly

Engineering Contradiction:

Improveheat rejection capabilityVSAvoidsystem cost

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

The patent uses phase change materials that can be integrated directly into the laser crystal cooling structure. This approach eliminates the need for expensive refrigeration systems, large pumps, and complex closed-loop cooling infrastructure, significantly reducing system cost while maintaining effective heat rejection capability.

Inventive Principle:

Principle #36Phase transitions

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 system provides effective cooling with reduced size, weight, and vibration, facilitating the use of high energy solid state lasers on mobile platforms and enabling more powerful and economical systems by optimizing coolant conditioning and flow management.

Implementation Method 1

Heat absorbed from the laser by the coolant is subsequently, e.g., between laser firings and/or immediately prior to reuse, transferred from the coolant to a phase change medium

Methodology Applied

Scientific EffectHeat transfer: Heat Exchanger

Implementation Method 2

transferred from the coolant to a phase change medium

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 3

A thermal management system utilizing a phase change medium heat exchanger and pressurized gas to condition coolant between laser shots

Methodology Applied

Scientific EffectPressurized gas flow: Pressure Gradient

Data Source

PatentUS8023542B2High energy laser thermal management

Publication Date: 2011.09.20 THE BOEING CO

AI summary

Methods and systems are disclosed for cooling a laser, such as a high average power (HAP) solid state laser (SSL). A coolant that has been heated from previous use can be conditioned by transferring heat from the coolant to a phase change medium. The conditioned coolant can then be re-used to cool the laser. In this manner, a low cost, lightweight, compact cooling system that generates comparatively quiescent flow at comparatively high flow rates can be provided.