Porous Heat Insulating Layer That Blocks Radiation Without Heat Paths
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Solution Overview
Problem
Conventional heat insulating members using silica aerogels face challenges in maintaining high heat insulation at high temperatures due to the formation of heat transfer paths when infrared shielding particles and inorganic fibers are blended, leading to increased thermal conductivity and reduced insulation effectiveness.
Innovation Solution
A heat insulating member with a specific composition comprising a porous structure, infrared shielding particles, and inorganic fibers, where the content of inorganic fibers is 5-25% by mass, infrared shielding particles is 10% or more, the total content of the porous structure and infrared shielding particles is 70% or more, and the ratio of the porous structure to infrared shielding particles is 1.2 or more, inhibiting the formation of heat transfer paths and enhancing radiation blocking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If infrared shielding particles are blended into the heat insulating layer, then radiation heat transfer is blocked, but heat transfer paths are formed between particles, increasing thermal conductivity
Solution Approach 1:
The patent uses inorganic fibers as intermediary materials between infrared shielding particles. These fibers physically separate the particles, preventing direct contact and heat transfer path formation while allowing the particles to maintain their radiation blocking function. The inorganic fibers act as thermal barriers that interrupt conductive heat transfer between particles.
Solution Approach 2:
The patent creates a composite heat insulating layer combining infrared shielding particles, inorganic fibers, and binder in specific proportions. This composite structure leverages the radiation blocking capability of particles while using fibers to maintain structural integrity and prevent particle-to-particle thermal conduction, achieving synergistic heat insulation performance.
2Strength
If inorganic fibers are added to the heat insulating layer, then structural integrity is improved, but heat transfer paths are more likely to form between fibers and particles
Solution Approach 1:
The patent optimizes the content ratio of inorganic fibers to infrared shielding particles, specifying that fiber content should be 5-25% by mass. This parameter control ensures sufficient structural integrity while limiting the formation of continuous heat transfer paths. The specific ratio range balances mechanical strength requirements with thermal insulation performance.
3Object-affected harmful factors
If the content of infrared shielding particles is increased, then radiation blocking is enhanced, but thermal conductivity increases due to more particle connections
Solution Approach 1:
Inorganic fibers serve as intermediary materials that physically separate infrared shielding particles even at high particle concentrations. This mediation allows the formulation to achieve high radiation blocking capability while preventing the formation of continuous thermal conduction networks between particles, thereby maintaining low thermal conductivity.
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 composition effectively prevents heat transfer by radiation and the formation of heat transfer paths, achieving high heat insulation both at room and high temperatures, with thermal conductivity below 0.3 W/m-K, thereby improving the overall insulation performance.
Implementation Method 1
A silica aerogel has a plurality of fine silica particles connected to form a skeleton, and has pores smaller than the mean free path of air between the skeletons. Among three forms of heat transfer (conduction, convection, and radiation), mainly convection is prevented by this fine porous structure
Implementation Method 2
Radiation is a phenomenon in which heat is transferred by electromagnetic waves, and the higher the temperature, the greater the emitted radiant energy. Therefore, in a high-temperature atmosphere, radiation becomes the main factor of heat transfer. Accordingly, at high temperatures, it is difficult to obtain desired heat insulation with only a silica aerogel, and blending in infrared shielding particles is effective
Data Source
AI summary
A heat insulating member includes a heat insulating layer containing: a porous structure that has a plurality of particles connected to form a skeleton, has pores in an inside, and has a hydrophobic site on at least a surface between the surface and the inside; infrared shielding particles; and inorganic fibers, the heat insulating layer satisfying the following conditions (a) to (d) with a total mass of the heat insulating layer as 100% by mass. (a) A content of the inorganic fibers is 5% by mass or more and 25% by mass or less. (b) A content of the infrared shielding particles is 10% by mass or more. (c) A total content of the porous structure and the infrared shielding particles is 70% by mass or more. (d) A ratio of a content of the porous structure to the content of the infrared shielding particles is 1.2 or more.