Evaporating Unit Layout for Uniform Two-Phase Power Electronics Cooling
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Solution Overview
Problem
Current two-phase cooling systems for power electronic devices face challenges in achieving efficient cooling while maintaining compactness and reducing costs, with issues such as temperature non-uniformities and premature device failure due to sub-cooled liquids causing hot spots.
Innovation Solution
The design of an evaporating unit with a thermo-conducting wall and a pre-heating mechanism that positions the inlet channel outside the cooling surface portion, pre-heating the cooling fluid to a temperature close to its liquid-gas phase transition point to prevent hot spots and enhance cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a two-phase cooling circuit is used to cool power electronic devices, then cooling performance is improved, but temperature non-uniformities and hot spots occur due to sub-cooled liquids
Solution Approach 1:
The inlet channel is positioned to allow the cooling fluid to be pre-heated by the heat emitting device before entering the evaporation channels. This preliminary heating action raises the fluid temperature closer to saturation, preventing sub-cooled liquid conditions that cause hot spots and temperature non-uniformities during evaporation
Solution Approach 2:
The inlet channel acts as an intermediary component between the heat emitting device and the evaporation channels. It mediates the thermal interaction by allowing the cooling fluid to absorb preliminary heat from the device through thermal conduction before the fluid enters the evaporation zone, thereby preparing the fluid for more uniform evaporation
2Volume of moving object
If the inlet channel is positioned inside the cooling surface portion, then compactness is achieved, but hot spots and premature device failure occur
Solution Approach 1:
The evaporating unit is designed with spatially differentiated zones: the inlet channel is positioned in a non-cooling region outside the cooling surface portion, while the evaporation channels are positioned within the cooling surface. This local quality differentiation allows the inlet channel to perform pre-heating without interfering with the uniform cooling function of the evaporation zones
Solution Approach 2:
The inlet channel is positioned in a different spatial dimension relative to the cooling surface portion - specifically outside the convex hull of the evaporation channels' projections. This dimensional positioning allows thermal interaction with the heat emitting device while preventing direct interference with the evaporation cooling zones, avoiding hot spots
3Device complexity
If cooling fluid is not pre-heated, then system complexity is reduced, but temperature non-uniformities cause premature device failure
Solution Approach 1:
The pre-heating function is merged into the existing inlet channel structure of the evaporating unit. The inlet channel serves dual purposes: delivering cooling fluid to the evaporation channels and simultaneously pre-heating the fluid through thermal conduction from the heat emitting device. This integration adds minimal complexity while significantly improving reliability
Solution Approach 2:
The heat emitting device itself serves as the heat source for pre-heating the cooling fluid. The device's own thermal energy is utilized to prepare the cooling fluid, eliminating the need for separate external pre-heating systems. This self-service approach improves reliability without proportionally increasing 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 solution improves cooling efficiency by maintaining the cooling fluid close to its saturation point, reducing temperature non-uniformities, and extending the lifespan of heat emitting devices by preventing premature failures.
Implementation Method 1
The liquid is heated inside of the evaporating unit by the dissipated heat from the heat emitting device and reaches a boiling temperature
Implementation Method 2
The vapour of the liquid is then guided through a vapour riser pipe system to a condenser. Within the condenser the vapour is changed into a liquid by emitting heat
Implementation Method 3
a thermo-conducting wall that is thermally connectable to the at least one heat emitting device
Implementation Method 4
As the temperature of the liquid will not rise above the boiling temperature, the temperature of the liquid and therefore the temperature of the heat emitting device is kept at a temperature of the boiling point of the liquid as a maximum
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
According to the present disclosure, an evaporating unit (40a) for cooling a heat emitting device (10) is provided. Typically, a cooling circuit (20a) comprises a stack (22) of evaporating units (40a) arranged in alternation with heat emitting devices (10). Each evaporating unit (40a) is connected to a condenser (80) and comprises a first inlet channel (43a), a first plurality of evaporation channels (45a), and a first outlet channel (50a). The evaporating unit (40a) is designed to pre-heat the cooling fluid flowing therein.