Back Iron Heat Exchanger Two-Phase Cooling for Electric Motors

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Solution Overview

Problem

Conventional electric motor cooling systems, such as those using ram air, are inefficient in hot and humid conditions, necessitating improved heat transfer control and efficiency.

Innovation Solution

An electric motor cooling system that introduces a mixture of liquid coolant and air into a back iron heat exchanger, where the liquid coolant converts to a gas to absorb thermal energy, with the option of a closed or open loop system, including a condenser for recycling or releasing the gas coolant, and a fluid mixer to optimize the cooling mixture.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If liquid coolant is introduced into the back iron heat exchanger to absorb thermal energy through phase change, then thermal transfer efficiency is improved, but device complexity increases due to additional components such as fluid mixer and condenser

Engineering Contradiction:
Improvethermal transfer efficiencyVSAvoiddevice complexity
Core Design Contradiction:
TemperatureVSDevice complexity

Solution Approach 1:

The patent utilizes the phase transition of liquid coolant to gas phase within the back iron heat exchanger to absorb thermal energy. This phase change process enables highly efficient heat transfer from the motor components, directly addressing the thermal management challenge while maintaining a relatively simple system architecture.

Inventive Principle:
Principle #36Phase transitions

Solution Approach 2:

The patent introduces a fluid mixer as an intermediary component that combines liquid coolant and air to create a cooling mixture before it enters the heat exchanger. This intermediary substance optimizes the cooling process by enhancing heat transfer efficiency and controlling the phase change behavior within the back iron heat exchanger.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If a closed loop system with condenser is used to recycle gas coolant, then cooling performance is enhanced through continuous cooling mixture supply, but device complexity and cost increase

Engineering Contradiction:
Improvecooling performanceVSAvoiddevice complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The closed loop system with condenser implements a feedback mechanism where exhaust gases are condensed back to liquid form and recycled into the cooling process. This feedback loop ensures continuous supply of cooled liquid coolant to the heat exchanger, maintaining optimal cooling performance and thermal management reliability.

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The condenser recovers the thermal energy and mass from the exhaust gases by condensing them back to liquid form. This recovery process eliminates waste of cooling medium and maintains continuous operation, improving reliability while the system can be configured as open or closed loop to balance complexity and performance needs.

Inventive Principle:
Principle #34Discarding and recovering

3Manufacturing precision

If fluid mixer is used to create optimal cooling mixture, then heat transfer control is improved, but manufacturing complexity increases

Engineering Contradiction:
Improveheat transfer controlVSAvoidease of manufacture
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The fluid mixer performs preliminary action by pre-mixing the liquid coolant with air to create an optimized cooling mixture before it enters the back iron heat exchanger. This preliminary mixing ensures proper composition and distribution of the cooling medium, improving heat transfer control and efficiency while using a relatively simple mixing mechanism.

Inventive Principle:
Principle #10Preliminary action

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

Enhances thermal transfer efficiency by leveraging the phase change of the liquid coolant and controlled mixing of air and liquid, providing superior cooling performance compared to traditional methods.

Implementation Method 1

allowing the liquid coolant to convert to a gas coolant within the back iron heat exchanger of the electric motor for absorbing additional thermal energy due to the phase change of the liquid coolant to a gas phase

Methodology Applied
Scientific EffectPhase change: Phase Change

Implementation Method 2

allowing the liquid coolant to convert to a gas coolant within the back iron heat exchanger of the electric motor for absorbing additional thermal energy due to the phase change of the liquid coolant to a gas phase

Methodology Applied
Scientific EffectEvaporation: Evaporation

Implementation Method 3

The system can further include a condenser configured to condense the gas coolant back to a liquid coolant downstream of the fluid outlet

Methodology Applied
Scientific EffectCondensation: Condensation

Data Source

PatentEP3015806B1Two-phase electric motor cooler
Publication Date: 2022.08.24 HAMILTON SUNDSTRAND CORP
  • EP3015806B1 patent drawingFigure 1
  • EP3015806B1 patent drawingFigure 2

AI summary

An electric motor system 100 includes a motor housing 101 and a stator core 103 disposed within the motor housing 101. The stator core 103 includes a back iron heat exchanger 105 for passing fluid therethrough. A fluid inlet 109 is disposed at a first portion 105a of the back iron heat exchanger 105 that is at least partially in fluid communication with a liquid coolant source and is configured to accept a cooling mixture. A fluid outlet 115 is disposed at a second portion 105b of the back iron heat exchanger 105 for outletting a gas coolant from the back iron heat exchanger 105 such that liquid coolant is convertible to the gas coolant in the back iron heat exchanger105 by receiving energy from the stator core 103 allowing the gas coolant exit through the outlet 115 and thereby removing heat from the stator core 103.