Analysis: various performance indicators of thermal insulation materials

The performance indicators of thermal insulation materials mainly include: thermal conductivity, bulk density, maximum service temperature, compressive strength, water content, coefficient of linear expansion, flexural strength and pH. Let us introduce what is the meaning of each indicator?

The performance indicators of thermal insulation materials mainly include: thermal conductivity, bulk density, maximum service temperature, compressive strength, water content, coefficient of linear expansion, flexural strength and pH. Let us introduce what the meaning of each indicator is:

1, thermal conductivity

Thermal conductivity is the thermal conductivity. The property of the heat transfer material to transfer heat is called thermal conductivity. It is a parameter of the ability of the thermal insulation material to transfer heat, reflecting the thermal conductivity of the material, and is the main thermophysical property of the thermal insulation material. Thermal conductivity is closely related to other physical properties of the material, such as density and moisture content, and is related to the internal structure of the material and to the size of the insulation layer.

2, the weight

The mass per unit volume of the insulating material that has been dried and is in a loose state at a temperature of l lOoC is the bulk density of the material. It has the problem of an optimum bulk density value, that is, it has a small thermal conductivity and a good thermal insulation effect under the optimum bulk density. In order to save energy and reduce the structural load of the insulated pipe and hanger structure in the project, insulation materials with small bulk density should be used as much as possible. Generally, the bulk density of soft and semi-rigid materials shall not exceed 150kg/m3, and the bulk density of hard materials shall not exceed 220kg/m3.

3, the maximum use temperature

The maximum operating temperature refers to the extreme temperature that the insulating material can withstand long-term safe and reliable operation. The use temperature of general insulation materials refers to the long-term use of insulation materials at this temperature, and its physical and chemical properties are stable, in line with the technical requirements of design and operation.

4, compressive strength and flexural strength

Compressive strength is the maximum pressure load per unit of original cross-section when the material is damaged by compressive forces. The compressive strength of the material is closely related to the processing technology and the porosity of the material. "Technical Guidelines for Equipment and Pipe Insulation") (GB 4272-92) stipulates that the compressive strength of hard products should not be less than 0.3 MPa. For soft, semi-rigid and loose insulation materials, it will not be subjected to compressive load. Damage, so the compressive strength is not specified. The flexural strength is the moment of force per unit area when the material is destroyed by the bending load.

5, water content

The property of the insulating material to absorb water is called water absorption. The degree of water absorption per unit volume of the material is expressed by the water absorption rate. The hygroscopicity of the thermal insulation material has a great influence on the thermal insulation effect. The absorbed water vapor will condense into water or form ice when it is cold, thereby greatly improving its thermal conductivity and even causing material cracking and destroying the thermal insulation structure. In addition, in order to reduce the moisture absorbed by the thermal insulation material, in addition to the waterproofing during construction, it is also possible to appropriately add a water repellent agent such as a swill mineral wool board and a hydrophobic perlite.

6, linear expansion coefficient

The expansion characteristics of the heat insulating material when heated may be expressed by a coefficient of linear expansion. The coefficient of linear expansion of the insulation material is closely related to the thermal stability of the material. If the linear expansion coefficient of the material is large, after the thermal insulation structure is heated, the internal deformation will generate a large stress, and when the temperature changes drastically, the thermal insulation structure will be damaged. When designing the insulation structure, a certain size expansion joint should be reserved according to the linear expansion coefficient of the material.

7, PH value

Insulation materials used in thermal equipment and piping shall not have chemical corrosive effects on metal surfaces. Generally, the insulation material must be neutral or PH value greater than 7-8, and must not contain soluble chloride. The content of sulfur oxides must not exceed 0.06%. The material should be in a dry state before use.

8, fire performance

It can be expressed by combustion performance, smoke density, toxicity index, and the like. The current materials all have certain fire performance, are incombustible, and do not produce toxic gases at high temperatures.

9, sound absorption coefficient

The ratio of the acoustic energy absorbed by the material to the incident acoustic energy. This indicator has a considerable impact on the noise of equipment and buildings. For example, the air conditioning system of a building, through the composite insulation of equipment and pipelines, selects materials with high sound absorption coefficient, which will greatly reduce the noise hazard.

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