Detailed data collection of thermal insulation materials

Thermal insulation material can block heat transfer, also called thermal insulation material. Traditional thermal insulation materials, such as glass fiber, asbestos, rock wool, silicate, etc. New thermal insulation materials, such as aerogel felt, vacuum board, etc.

Basic introduction Chinese name: thermal insulation material mbth: Keeprecision thermal insulation? Function: Materials that can prevent heat transfer are also called insulation materials. Also called nano-airbag reflective layer. Usage: steel structure room/heat pipe packaging, etc. Introduction, principle, influencing factors, material type, working temperature, moisture content, pore characteristics, bulk density, material particle size, heat flow direction, filling gas, specific heat capacity, vacuum, representative materials. Introduction: Thermal insulation materials are divided into porous materials, thermal reflective materials and vacuum materials. The former uses the pores contained in the material itself for heat insulation, because the thermal conductivity of air or inert gas in the gap is very low, such as foam materials and fiber materials; Thermal reflective materials have high reflection coefficient and can reflect heat, such as gold, silver, nickel, aluminum foil or metallized polyester, polyimide film, etc. Vacuum heat insulation material is to use the vacuum inside the material to block convection and thus heat insulation. The aerospace industry has strict requirements on the weight and volume of thermal insulation materials, and often requires them to have sound insulation, vibration reduction, corrosion resistance and other properties. Different aircraft have different requirements for thermal insulation materials. Foam plastics, superfine glass wool, high-silicon wool and vacuum insulation panel are commonly used in aircraft cockpit and cockpit insulation. The thermal insulation material of early missile head was phenolic foam. With the application of polyurethane foam with good temperature resistance, a single thermal insulation material has developed into a sandwich structure. The thermal insulation method of missile instrument cabin is to coat a millimeter-thick foam coating on the outer skin of the cabin as an anti-corrosion coating at room temperature. When pneumatic heating reaches above 200℃, it will bubble evenly and play a role in heat insulation. When the artificial earth satellite moves in the alternating environment of high temperature and low temperature, it needs to use multi-layer heat insulation materials with high reflectivity, which generally consists of dozens of aluminum-plated films, aluminum-plated polyester films and aluminum-plated polyimide films. In addition, the development of surface heat insulation tile successfully solved the heat insulation problem of space shuttle, which also marked the higher development level of heat insulation materials. Aerogel felt is a new type of thermal insulation material. It is a porous material with nanometer pore size, which is mostly used for pipeline insulation and equipment insulation. The thermal conductivity of this material is 0.0/||| 0/8W/(k m) at room temperature and 0.009W/(k m) at low temperature. Vacuum insulation board is the latest insulation material, which has been widely used abroad, mostly in household appliances industry. The thermal conductivity of this material is extremely low, only 0.004, so it has an outstanding effect in heat preservation and energy saving. At present, this material has been completely used in household freezers and refrigerated containers. Najib thermal insulation soft felt is a kind of soft industrial thermal insulation material with strong thermal insulation performance. There are three ways of principle heat transfer in building heat transfer: conduction heat+convection heat; 75%。 After the temperature of tile roof rises in summer, a large amount of radiant heat enters the room, which leads to the continuous rise of temperature and extremely uncomfortable working and living environment. The solar radiation absorption coefficient (normal total radiation emissivity) of aluminum foil coil is 0.07, and the radiation heat is very small. It is widely used for heat insulation of roofs and walls. Heat energy transmission way (without heat insulation film): the sun-infrared electromagnetic wave-heat energy hits the tiles to raise the temperature-tiles become heat sources to release heat energy-heat energy hits the cast-in-place roof to raise the temperature-cast-in-place roof becomes heat sources to release heat energy-indoor ambient temperature continues to rise. Heat energy transfer path (with heat insulation film): solar-infrared electromagnetic wave-heat energy hits the ceramic tile to raise the temperature-ceramic tile becomes a heat source to release heat energy. Influencing factors: Different types of materials and thermal insulation materials (thermal insulation materials) have different thermal conductivity. The physical and thermal properties of thermal insulation materials are different because of their different material compositions. There are differences in heat insulation mechanism, and their thermal conductivity or thermal conductivity are also different. Even the thermal insulation materials with the same material have different internal structures or different production control processes, and the thermal conductivity sometimes varies greatly. For solid thermal insulation materials with low porosity, the thermal conductivity of crystalline structure is the largest, followed by microcrystalline structure and glass structure is the smallest. However, for thermal insulation materials with high porosity, gas (air) plays a major role in the thermal conductivity, and the solid part has little influence on the thermal conductivity regardless of the crystalline structure or the glassy structure. The working temperature has a direct influence on the thermal conductivity of various thermal insulation materials. With the increase of temperature, the thermal conductivity of the material increases. Because when the temperature rises, the thermal motion of solid molecules in the material increases, and at the same time, the heat conduction of air in the pores of the material and the radiation between the pore walls also increase. However, in the temperature range of 0-50℃, this effect is not significant, and the temperature effect should be considered only for materials at high temperature or negative temperature. Most moisture-containing thermal insulation materials have porous structure and are easy to absorb moisture. After the material absorbs water, the thermal conductivity increases. When the water content is more than 5%- 10%, the increase of thermal conductivity is most obvious in porous materials. This is because when there is water (including water vapor) in the pores of the material, the diffusion of steam in the pores and the movement of water molecules will play a major role in heat transfer, and the thermal conductivity of water is about 20 times greater than that of air, resulting in an obvious increase in its effective thermal conductivity. If the water in the pores becomes ice, the thermal conductivity of the ice is greater, and as a result, the thermal conductivity of the material is greater. Therefore, non-hydrophobic thermal insulation materials must be waterproof and moisture-proof when applied. With the same porosity, the larger the pore size, the greater the thermal conductivity. The thermal conductivity of connected pores is higher than that of closed pores, and the higher the porosity of closed pores, the lower the thermal conductivity. Bulk density Bulk density (or specific gravity, density) is a direct reflection of the porosity of materials. Because the thermal conductivity of gas phase is usually smaller than that of solid phase, thermal insulation materials often have higher porosity, that is, lower bulk density. Generally speaking, increasing porosity or decreasing bulk density will lead to the decrease of thermal conductivity. However, for materials with low apparent density, especially fibrous materials, when the apparent density is below a certain limit, the thermal conductivity will increase, because when the porosity increases, the connected pores will increase greatly, thus strengthening convection. Therefore, this material has an optimal apparent density, that is, the thermal conductivity is the smallest at this apparent density. When the particle size of the material is at room temperature, the thermal conductivity of the loose particle material decreases with the decrease of the particle size. When the particle size is larger, the gap size between particles increases, and the thermal conductivity of air will inevitably increase. In addition, the smaller the particle size, the smaller the influence of temperature change on its thermal conductivity. The relationship between thermal conductivity and heat flow direction only exists in anisotropic materials, that is, materials with different structures in all directions. From the arrangement state, fibrous materials can be divided into two situations: the direction is perpendicular to the heat flow direction and the fiber direction is parallel to the heat flow direction. The heat insulation performance when the heat transfer direction is perpendicular to the fiber direction is better than that when the heat transfer direction is parallel to the fiber direction. Generally speaking, the fiber arrangement of fiber insulation materials is the latter or close to the latter, and its thermal conductivity is much smaller than other forms of porous insulation materials at the same density. For anisotropic materials (such as wood), when the heat flow is parallel to the fiber direction, the resistance is small; When perpendicular to the fiber direction, the resistance is greater. Taking pine as an example, the thermal conductivity is 0./|||| 0/7 w/(m k) when the heat flow is perpendicular to the wood grain, and 0.35 w/(m k) when it is parallel to the wood grain. Porous materials can be divided into two types: solid materials with bubbles and solid materials with slight contact between particles. Thermal insulation materials with a large number or countless multi-opening pores have worse thermal insulation performance than materials with a large number of closed pores, because the direction of pore communication is closer to the direction of heat transfer. In inflatable thermal insulation materials, most of the heat is conducted from the gas in the pores. Therefore, the thermal conductivity of thermal insulation materials depends largely on the type of filling gas. If helium or hydrogen is filled in cryogenic engineering, it can be regarded as a first-order approximation. It is considered that the thermal conductivity of thermal insulation materials is equivalent to these gases, because the thermal conductivity of helium and hydrogen is relatively large. Specific heat capacity and thermal conductivity = thermal diffusion coefficient × specific heat × density. Under the same thermal diffusion coefficient and density, the greater the specific heat, the higher the thermal conductivity. The specific heat of thermal insulation materials is related to the calculation of the required cooling capacity (or heat) of thermal insulation structures during cooling and heating. At low temperature, the specific heat of all solids changes greatly. At normal temperature and pressure, the mass of air does not exceed 5% of the mass of thermal insulation material, but with the decrease of temperature, the proportion of gas is increasing. Therefore, this factor should be considered when calculating thermal insulation materials working under normal pressure. For commonly used thermal insulation materials, among the above factors, apparent density and humidity have the greatest influence. Therefore, when determining the thermal conductivity of materials, the apparent density of materials must be determined at the same time. With regard to humidity, for most thermal insulation materials, the equilibrium humidity of the material when the relative humidity of air is 80%-85% can be taken as the reference state, and the thermal conductivity of the material should be determined as far as possible under this humidity condition. There are three ways of vacuum heat conduction: convection, conduction and radiation. Among them, convection heat conduction is the most important. Vacuum blocks convection and the thermal conductivity is greatly reduced. The principle is like a thermos bottle. However, the filler material as the skeleton may conduct heat by conduction, so glass fiber with low thermal conductivity is used as the skeleton. The outer surface is covered with aluminum film packaging bag to block radiation. So this material has the lowest thermal conductivity. Dike aluminum foil thermal insulation coiled material represents the concept of aluminum foil thermal insulation coiled material, which is also called barrier film, thermal insulation film, thermal insulation foil, heat absorption film, reflective film and so on. It is made of aluminum foil veneer+polyethylene film+fiber braid+metal coating laminated by hot melt adhesive. Aluminum foil coil has the functions of heat insulation, waterproof and moistureproof. Aluminum foil thermal insulation coiled material has extremely low solar radiation absorption coefficient (0.07) and excellent thermal insulation performance, which can reflect more than 93% of radiant heat, so it is widely used for thermal insulation of building roofs and external walls. Several thermal insulation materials with low thermal conductivity (divided by thickness) 1. Thermal insulation paper: Fibergc-/|||| 0/0 ~ 50 series thermal insulation paper has a thermal conductivity of 0.027W and a thickness of 0.4~5mm, which is white and paper-like, and has the advantage of ultra-thin. IT is often used in IT small electronic products and household appliances, and rarely used for building insulation. 2. Glass fiber cotton board/felt: the thermal conductivity is 0.035W, the thickness is 3mm~5mm, it is white, and it is divided into hard board and soft felt. The glass fiber structure is used in household appliances, pipelines, etc. 3. Polyurethane foam board (PU/PIR): thermal conductivity is 0.02~0.035 Watt-meter, multicolor, hard and brittle, and thickness is/||||| 0/0 mm ~ 200mm; 4. Centrifugally peeled fiber wool/rock wool: the thermal conductivity is generally 0.038 W, the thickness is 30~200mm, and it is yellow, which is used in construction, computer rooms, warehouses, etc. 5. Micro-nano insulation board: thermal conductivity of 0.02 watts, high temperature resistance, mostly used in high temperature environment; 6. Aerogel felt: at room temperature, the thermal conductivity is 0.0/||| 0/8W/(k m), the thickness is 2mm ~ |||| 0/0mm, it is white or blue, and it can be customized into a rigid plate as required, which is suitable for thermal insulation of equipment and pipelines. Thermal insulation material RFC special-shaped thermal insulation parts, with arbitrary shape. Traditional hot air drying is time-consuming, energy-consuming and poor in drying uniformity due to poor thermal conductivity. However, microwave drying technology bypasses the problem of poor thermal conductivity, improves production efficiency, meets the requirements of modern industrial production for high efficiency, energy saving and environmental protection, and solves the problems of long time, slow capital turnover and uneven drying of traditional thermal insulation materials. The specific characteristics are: ● The drying process is fast, and the deep drying can be completed in a few minutes. ● Uniform drying, good product drying quality; ● High efficiency, energy saving, safety and environmental protection; Low thermal inertia, easy to control the instantaneity of heating. Synotherm is a world-renowned manufacturer of industrial microwave kiln equipment and provider of microwave heating solutions, specializing in the production of fine microwave drying equipment and high-temperature microwave sintering furnaces. For more information, see.