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What is the thermal insulation principle of aerogel thermal insulation materials
Release time:
2021-11-18 17:27
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Aerogels, also known as xerogels, have a density of only 2.75 times the density of air, making it the densest solid in the world. Aerogels can be divided into carbon series, silicon series, sulfur series, metal oxide series, metal series, etc. according to their composition. However, the most developed and used silicon aerogel should be silica aerogel.
Aerogel is a new type of lightweight nanoporous product. It has a nanostructure (typical pore size is less than 50nm, skeleton particles are 1-20nm), large specific surface area (up to 800~1000m2/g), high porosity (can be Up to 80%~99.8%) and other characteristics. In addition, the high temperature of aerogel, generally at 800 ℃, has no obvious changes in structure and function. Therefore, aerogel has unparalleled superiority as a high-temperature insulation product.
Insulation principle of aerogel insulation products
(1) Convection: When the diameter of the pores in the aerogel is less than 70nm, the air molecules in the pores lose their ability to move freely and relatively adhere to the pore walls. At this time, the product is in an approximate vacuum state.
(2) Radiation: Because the pores in the aerogel are all nano-sized pores and the product itself has a very low volume density, the number of pore walls inside the product tends to be "infinitely large", and each pore wall is covered. The effect of the hot plate, therefore, is close to the "infinite number of heat shields" effect, which reduces the radiant heat transfer to almost the lowest limit.
(3) Heat conduction: Because of the existence of nearly infinite number of nanopores, the heat flow in the solid can only be transferred along the pore walls. The nearly infinite number of pore walls constitutes a nearly "infinitely long path" effect, which makes the solid heat conduction In order to drop to the lowest limit.
Compared with traditional thermal insulation products, nanoporous aerogel thermal insulation products can achieve equivalent thermal insulation effects with lighter weight and smaller volume. It has good thermal stability, thermal shock resistance and thermal insulation, which can replace the traditional mineral cotton, so that the house can be insulated and warm. If it is used in high-rise buildings, it can replace general curtain wall glass, greatly reduce the weight of the building, and can play a fire prevention effect. In addition, replacing traditional thermal insulation products with aerogel thermal insulation composite products on the top of pipelines, furnaces and other thermal equipment can greatly reduce heat loss. Applying nanoporous super insulation product aerogel to the storage tanks, pipes and collectors of solar water heaters, the heat collection efficiency can be increased by more than 1 times, and the heat loss is reduced to less than 30% of the current level. In addition, before and after use, it can insist on not powdering, not brittle, and not aging; it does not support the growth of mold, and the induction function remains unchanged for a long time; it has a long service life and can maintain the same life span as the building.
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