How to judge the quality of building insulation materials by fire equipment manufacturer of Shengao company?
发布时间:2021/6/19
When a fire breaks out, we can't do without fire-fighting equipment, but in order to reduce or avoid the loss caused by the fire, we should try our best to prevent the fire from happening. For example, understanding some fire knowledge can effectively prevent the occurrence of fire. Today, the fire equipment manufacturers of Shengao Company come to popularize the fire knowledge: How to judge the quality of building insulation materials?
2. Temperature
Temperature directly affects the thermal conductivity of various insulation materials, and the thermal conductivity of materials increases with the increase of temperature.
3. Particle size of loose material
At room temperature, the thermal conductivity of porous materials decreases with the decrease of particle size. When the particle size is large, the gap size between particles increases, and the thermal conductivity of the air between particles will inevitably increase. If the particle size is small, the temperature coefficient of thermal conductivity is small.
4. Bulk density
Bulk density is a direct reflection of material porosity, because the thermal conductivity of gas phase is usually less than that of solid phase, so the porosity of thermal insulation material is larger, that is, the bulk density is smaller. Generally, increasing the porosity or decreasing the bulk density will lead to the decrease of the thermal conductivity.
5. Effect of filling gas
In thermal insulation materials, most of the heat is transferred from the gas in the pores. Therefore, the thermal conductivity of insulation materials depends largely on the type of filling gas. If helium or hydrogen is filled in cryogenic engineering, it can be regarded as the first order approximation. Because the thermal conductivity of helium and hydrogen is relatively large, it is considered that the thermal conductivity of thermal insulation materials is equal to that of these gases.
6. Direction of heat flow
The relationship between thermal conductivity and heat flow direction only exists in anisotropic materials, that is, different materials are constructed in different directions. When the heat transfer direction is perpendicular to the fiber direction, its adiabatic performance is better than that when the heat transfer direction is parallel to the fiber direction. Similarly, the thermal insulation performance of the material with a large number of closed holes is better than that of the material with a large number of open holes. Porous materials can be further divided into two types: bubbles in slight contact with each other and solid particles. The arrangement of fiber materials can be divided into two cases: the direction is perpendicular to the heat flow direction, and the fiber direction is parallel to the heat flow direction. Generally, the fiber arrangement of fiber insulation material is the latter or close to the latter. At the same density, its thermal conductivity is much smaller than other porous insulation materials.
7. Coefficient of linear expansion
In order to calculate the stability and firmness of insulation structure during cooling (or heating), it is necessary to know the linear expansion coefficient of insulation material. If the linear expansion coefficient of insulation material is small, the possibility of damage to insulation structure due to thermal expansion and cold shrinkage is small. The coefficient of linear expansion of most insulation materials decreases significantly with the decrease of temperature.
8. Specific heat capacity
The specific heat capacity of insulating materials is related to the cooling capacity (or heat) required for calculating the cooling and heating of insulating structures. At low temperature, the specific heat capacities of all solids vary greatly.
Under normal temperature and pressure, the air quality does not exceed 5% of the insulation material, but with the decrease of temperature, the proportion of gas is increasing. Therefore, this factor should be considered in the calculation of thermal insulation materials working at atmospheric pressure.
1. Moisture content
All insulation materials have porous structure, easy to absorb moisture. When the moisture content is more than 5% ~ 10%, the moisture content of the material occupies part of the air filled pore space after absorbing moisture, which leads to the significant increase of its effective thermal conductivity.2. Temperature
Temperature directly affects the thermal conductivity of various insulation materials, and the thermal conductivity of materials increases with the increase of temperature.
3. Particle size of loose material
At room temperature, the thermal conductivity of porous materials decreases with the decrease of particle size. When the particle size is large, the gap size between particles increases, and the thermal conductivity of the air between particles will inevitably increase. If the particle size is small, the temperature coefficient of thermal conductivity is small.
4. Bulk density
Bulk density is a direct reflection of material porosity, because the thermal conductivity of gas phase is usually less than that of solid phase, so the porosity of thermal insulation material is larger, that is, the bulk density is smaller. Generally, increasing the porosity or decreasing the bulk density will lead to the decrease of the thermal conductivity.
5. Effect of filling gas
In thermal insulation materials, most of the heat is transferred from the gas in the pores. Therefore, the thermal conductivity of insulation materials depends largely on the type of filling gas. If helium or hydrogen is filled in cryogenic engineering, it can be regarded as the first order approximation. Because the thermal conductivity of helium and hydrogen is relatively large, it is considered that the thermal conductivity of thermal insulation materials is equal to that of these gases.
6. Direction of heat flow
The relationship between thermal conductivity and heat flow direction only exists in anisotropic materials, that is, different materials are constructed in different directions. When the heat transfer direction is perpendicular to the fiber direction, its adiabatic performance is better than that when the heat transfer direction is parallel to the fiber direction. Similarly, the thermal insulation performance of the material with a large number of closed holes is better than that of the material with a large number of open holes. Porous materials can be further divided into two types: bubbles in slight contact with each other and solid particles. The arrangement of fiber materials can be divided into two cases: the direction is perpendicular to the heat flow direction, and the fiber direction is parallel to the heat flow direction. Generally, the fiber arrangement of fiber insulation material is the latter or close to the latter. At the same density, its thermal conductivity is much smaller than other porous insulation materials.
7. Coefficient of linear expansion
In order to calculate the stability and firmness of insulation structure during cooling (or heating), it is necessary to know the linear expansion coefficient of insulation material. If the linear expansion coefficient of insulation material is small, the possibility of damage to insulation structure due to thermal expansion and cold shrinkage is small. The coefficient of linear expansion of most insulation materials decreases significantly with the decrease of temperature.
8. Specific heat capacity
The specific heat capacity of insulating materials is related to the cooling capacity (or heat) required for calculating the cooling and heating of insulating structures. At low temperature, the specific heat capacities of all solids vary greatly.
Under normal temperature and pressure, the air quality does not exceed 5% of the insulation material, but with the decrease of temperature, the proportion of gas is increasing. Therefore, this factor should be considered in the calculation of thermal insulation materials working at atmospheric pressure.
