Porous Oxide Heat-Transfer Surface for Sustained Coolant Boiling
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Solution Overview
Problem
Coolant resistance to boiling in cooling systems leads to reduced heat transfer and increased equipment temperature, particularly in systems with repeated boiling or long-term immersion, due to increased superheating near the heat-dissipating surface.
Innovation Solution
A heat-transfer member with a base material composed of an inorganic compound and an oxide layer featuring pores with specific dimensions and configurations, formed through a two-stage anodic oxidation process, promoting coolant boiling and bubble separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a boiling heat-transfer surface with recessed and protruding parts is used to promote coolant boiling, then coolant boiling is promoted initially, but the coolant becomes resistant to boiling after repeated boiling or long-term immersion
Solution Approach 1:
The patent applies porous materials by forming a porous oxide layer on the heat-transfer surface through anodic oxidation. This porous structure with controlled pore sizes (5-70 nm openings) and depths (600 nm - 20 μm) provides numerous nucleation sites for bubble formation, promoting sustained coolant boiling without the degradation issues of conventional recessed and protruding surfaces
Solution Approach 2:
The patent changes physical parameters by controlling pore diameter (5-70 nm), pore depth (600 nm - 20 μm), and oxide layer composition through anodic oxidation processing conditions. These parameter optimizations ensure the pores maintain gas pockets that promote boiling while resisting coolant penetration and degradation over time
2Productivity
If the coolant is boiled repeatedly or immersed for a long period, then heat transfer continues, but the degree of superheating increases and heat transfer efficiency decreases
Solution Approach 1:
The porous oxide layer with specific pore dimensions provides continuous nucleation sites that facilitate bubble formation at lower superheating degrees. The pore structure traps gas pockets that serve as bubble nuclei, enabling sustained efficient heat transfer even after repeated boiling cycles without significant superheating accumulation
Solution Approach 2:
The anodic oxidation process preliminarily creates the porous structure with optimal pore sizes and distributions before operation. This pre-formed structure ensures immediate and sustained bubble nucleation capability from the start of operation, preventing superheating buildup that would otherwise occur during initial heating phases
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 heat-transfer member maintains coolant-boiling-promoting effects for a long period by effectively vaporizing superheated coolant and separating bubbles, reducing coolant penetration and maintaining efficient heat transfer.
Implementation Method 1
Pores having such a shape are capable of promoting the vaporization of superheated coolant upon contact therewith, thereby generating numerous bubbles
Implementation Method 2
by performing an anodic oxidation process on the base material under first processing conditions, the oxide layer comprising the plurality of pores is formed on the surface of the base material
Implementation Method 3
causing the coolant, which has contacted the heat-dissipating surface of the heat-transfer member, to boil
Data Source
AI summary
A heat-transfer member (1) includes: a base material (2) that is composed of an inorganic compound containing a metal or a metal element; and an oxide layer (3) that is composed of an oxide or oxides of the metal element contained in the base material (2) and is formed on the base material (2). The oxide layer (3) has a plurality of pores (31), which include: first portions (312) that have openings (311) on the surface of the heat-transfer member (1), the openings (311) having an average opening diameter of 5 nm or larger and 70 nm or smaller; and second portions (313) that have an average pore diameter larger than the average opening diameter of the first portions (312) and are continuous with the first portions (312). The average depth of the second portions (313) is 600 nm or more and 20 μm or less.