Electric Machine Cooling With Two-Phase Refrigerant Cavities
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Solution Overview
Problem
Existing cooling systems for electric machines face challenges in effectively removing heat from all electrical components, particularly those with longer thermal conductive paths to the housing, leading to reduced power density and increased operating temperatures.
Innovation Solution
The implementation of a rotary mechanical system that utilizes a housing with both a liquid coolant and a sealed two-phase refrigerant to enhance heat transfer. The liquid coolant is circulated through a coolant cavity, while the two-phase refrigerant is sealed within an electrical cavity, facilitating heat transfer through convection and evaporation/condensation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a liquid coolant system is used to cool electrical components, then heat removal capability is improved, but components with longer thermal conductive paths still experience high operating temperatures
Solution Approach 1:
A two-phase refrigerant is introduced as an intermediary cooling medium between the electrical components and the liquid coolant system. The refrigerant absorbs heat directly from electrical components through evaporation, bypassing the limitation of long thermal conductive paths to the housing, and then transfers this heat to the liquid coolant through condensation in thermal contact with the coolant cavity.
Solution Approach 2:
The system utilizes phase transitions of a two-phase refrigerant (evaporation from liquid to vapor to absorb heat, and condensation from vapor to liquid to release heat) to enhance heat transfer efficiency. This allows effective cooling of electrical components regardless of their distance from the housing, as the refrigerant can absorb heat directly where it is generated.
2Device complexity
If electrical components are cooled through the housing structure, then system complexity is reduced, but heat transfer efficiency decreases for components with long thermal paths
Solution Approach 1:
The cooling system employs a nested structure where the electrical cavity containing the two-phase refrigerant is positioned within or adjacent to the coolant cavity. This nested arrangement allows the refrigerant to cool electrical components directly while the outer coolant cavity provides additional cooling capacity, maximizing heat transfer efficiency without significantly increasing overall system complexity.
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 allows for increased heat transfer to the liquid cooling system, enabling higher power density and lower operating temperatures in electric machines by effectively cooling all electrical components, including those with longer thermal paths.
Implementation Method 1
Another portion of the heat generated from electrical components may transfer to the housing by the refrigerant, such as through convection of a liquid phase of the refrigerant
Implementation Method 2
through evaporation and subsequent condensation of a vapor phase of the refrigerant against the wall of the housing or another cool surface coupled to the housing
Implementation Method 3
through evaporation and subsequent condensation of a vapor phase of the refrigerant against the wall of the housing or another cool surface coupled to the housing
Implementation Method 4
A portion of the heat generated by electrical components may transfer to the housing through thermal conduction, such as from portions of electrical components attached to the housing
Implementation Method 5
The liquid coolant removes heat from the housing
Data Source
AI summary
A rotary mechanical system includes an electric machine, such as an electric motor, and a housing at least partially housing one or more components of the electric machine. The housing defines an electrical cavity and a coolant cavity. The electrical cavity houses one or more electrical components, such as a stator, of the electric machine. The coolant cavity is configured to receive a liquid coolant, such as ethylene glycol and water, from a liquid coolant system. The housing is configured to seal a two-phase refrigerant within the electrical cavity to transfer heat from the one or more electrical components to a wall of the electrical cavity and from the wall of the electrical cavity to the liquid coolant.