Since the performance of insulation materials directly affects the energy consumption, weight, fire resistance, construction and price of refrigeration, air conditioning systems and air conditioning equipment, it is advisable to choose what kind of insulation materials for refrigeration and air conditioning pipelines and equipment. Controversial issues. On the other hand, in the process of selecting insulation materials, there are also some misunderstandings, such as the use of soft polyurethane foam as a high-grade insulation material, the use of rock wool board for air conditioning and refrigeration insulation, and due to improper selection of materials, due to insulation materials Fires caused by burning are not uncommon in China.
Therefore, the choice of insulation materials is a very important issue and should be given full attention.
1 Analysis of performance index of ice storage air conditioning insulation material 1.1 Thermal conductivity of insulation material. The thermal conductivity is a parameter that characterizes the ability of the insulation to transfer heat. It is defined as: lm thick object, when the temperature difference between the two sides is 1T, the heat transferred per unit area through heat conduction. Since the thermal conductivity varies with temperature, the average temperature at which the sample is tested must be given. The unit of thermal conductivity is W/(mK). The standard is the density of Japanese ISA1412. 2.2 insulation material. Density is the mass of insulation material per unit volume, and the unit is kg/m3. The density of insulation material not only affects the quality of pipelines and equipment, but also the cost of insulation materials. The standard is the water absorption rate of ISA9514. 2.3 insulation material. The water absorption rate refers to the mass ratio of the heat insulating material in a state of water saturation to a dry state. The thermal insulation material is a porous material. When moisture is contained, the thermal conductivity will rise sharply, the thermal insulation effect will be significantly deteriorated, and the density will also increase. Therefore, the water absorption rate is an important performance index of the thermal insulation material. The standard is ASTMC-64, ISA9514. 2.4 Fireproof performance of insulation materials The fire performance of insulation materials can be expressed by three indicators: combustion performance, smoke density and toxicity index. The detection method of combustion performance can be GB24o6-80 oxygen index method, GB24os-80 plastic burning performance test method and horizontal combustion method.
The smoke density test method can be GB8627-88 smoke density test method. There is no corresponding standard for the toxicity index. It can be implemented according to the physicochemical properties of the materials and the content of toxic substances in the chemical components produced during the volatile decomposition, with reference to the national permitted standards for health standards. Insulation materials should have good fire resistance, will not burn, and will not produce toxic gases at high temperatures.
2.6 Sound absorption coefficient of insulation material The ratio of the sound energy absorbed by the material to the incident sound energy. The sound absorption coefficient of the insulation material has a certain influence on the noise of the air conditioning equipment. For air-conditioning equipment, there are two main ways to spread the noise. One is to enter the room through the outer panel of the equipment, and the other is to enter the room through the air supply and return air. In general, the latter has far more impact than the former. If the inner side of the outer panel of the air-conditioning equipment adopts a heat-insulating material with a large sound absorption coefficient, the noise passing through the air-feeding and return air inlets will be significantly reduced due to the sound-absorbing effect. However, when the insulating material is sandwiched between the double-sided steel sheets, the sound absorption coefficient of the insulating material is less affected. On the other hand, since the outer plate of the air-conditioning equipment is generally a steel plate, a porous insulating material is adhered inside thereof, and the sound insulation effect of the outer plate is increased due to the damping effect, but the outer plates of different heat insulating materials and steel plates are combined. Sound insulation performance needs to be determined by calculation and experiment.
2.7 Mechanical strength of insulation materials. The ability of insulation materials to resist damage under external forces. Divided into tensile strength and compressive strength. The insulation material should have a certain compressive strength, which is not easily deformed or destroyed under the action of external force, and reduces the loss during transportation and installation. Standard ISA9514. 2.8 Anti-chemical properties of insulation materials Insulation materials should have certain chemical resistance, so that they can be deformed without being deformed by using different organic glues.
Insulation materials should not be easy to lose the function of foam due to aging and embrittlement. Ultraviolet radiation test is generally used (UV irradiation 20oh is equivalent to one year of natural exposure). That is, the long-term effects of raw materials used in insulation materials on the environment and humans, including the ability to destroy the ozone layer of the atmosphere, and the greenhouse effect. The insulation material should be easy to construct, and it is harmless to the workers during construction. At the same time, it should be considered that the use of a certain insulation material may improve or improve the processability of the insulation equipment. Refrigeration and air conditioning systems and equipment have a wide temperature range, and the larger the applicable temperature range of the insulation material, the wider the use. Insulation materials are generally applied at room temperature. If the coefficient of linear expansion is too large, the insulation material will shrink or expand when it encounters cold or heat, resulting in a gap, so it requires a certain dimensional stability.
3 ice storage air conditioning commonly used insulation materials performance characteristics and applications 3.1 rigid polyurethane foam is currently the best insulation properties of insulation materials, other insulation materials in addition to foam glass is poor, insulation performance is similar. However, it should be noted that the density has a greater impact on the thermal performance of the insulation material.
3.2 water absorption and moisture permeability. Water absorption and moisture permeability are an important performance index of insulation materials, especially for insulation materials used in refrigerating air conditioners. Because the surface temperature of refrigerated air-conditioning equipment and pipelines is generally below the air dew point, if the treatment is not good, the material may enter or damp, resulting in deterioration of insulation performance. Among the above six insulation materials, rigid polyethylene foam has the best water resistance, while rock wool is the worst. Rockwool is generally not suitable as a thermal insulation material for refrigerating air-conditioning equipment and pipelines, and is suitable for high-temperature equipment and pipeline insulation. When using centrifugal glass wool as the thermal insulation material for low-temperature refrigerating air-conditioning equipment and pipelines, attention should be paid to the joints of the thermal insulation materials, and the butt joints should be tight to prevent the hot and humid air from entering and forming condensation. In the domestic air-conditioning system using centrifugal glass wool pipe sleeves, large-scale condensation occurs, which is not uncommon. When centrifugal glass wool is used as the insulation material for the refrigerator, the moisture barrier should be placed inside the wall.
3.3 Fireproof performance of insulation materials. Due to the continuous fire accident caused by the ignition of the insulation material, the fire performance of the insulation material has been paid more and more attention. Although most of the current flammable insulation materials have been added with flame retardant in the production process, there are two problems that require attention. First, in order to reduce the production cost, some manufacturers do not add or add less flame retardant in the flammable insulation material, the consequences are very serious; second, even if some insulation materials increase the flame retardant, but because of the toxic fumes when burning, and drops Falling objects can cause fire, so you should pay attention to a reasonable range of use, such as rigid polyurethane foam and polystyrene foam should not be directly exposed to the air. The environmental problems caused by the foaming agent used in the production of thermal insulation materials have attracted the attention of the world, and this problem will eventually be solved.
3.4 The temperature of the insulation material used. The excellent processability of rigid polyurethane foam is one of the main reasons for making this insulation the most important refrigeration insulation material in the world. The flexible foaming process, strong adhesion to various materials, superior mechanical strength, greatly expands its application range. The temperature range of insulation used is an easily overlooked problem. Due to the excessive temperature of the heat carrier in the winter tube, the destruction of the insulation material sometimes occurs. Therefore, when the cold water pipe is used as a hot water pipe in winter or when the steam pipe is insulated, a reasonable insulation material should be properly selected.
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