Although the nano aerogel has the characteristics of low volume density, low thermal conductivity, low dielectric constant, high specific surface area and high porosity, and can be used as a good thermal insulation material, but at the same time, because of the shortcomings of simple nano aerogel, such as low strength, poor toughness and easy to break, the application of the nano aerogel in actual production is greatly limited. However, in recent years, the research on improving the flexibility of nano aerogels has been gradually increased. the flexible nano aerogels thermal insulation felt, nano aerogels thermal insulation board and other composite materials have been prepared and applied in energy-saving construction, metallurgy, aerospace and solar collectors and other industries. As an agricultural country in China, the thermal insulation of agricultural building facilities is a big difficulty in large-scale facility agricultural production. however, the research on the application of nano aerogel thermal insulation materials in agricultural buildings is almost blank at present. this paper discusses the application of several nano aerogel thermal insulation materials in agricultural buildings for future research.
1, nano aerogel thermal insulation felt is use as a thermal insulation material of a greenhouse enclosure structure
The insulation performance of greenhouse enclosure structure in winter has an important influence on the indoor temperature. in order to maintain the appropriate indoor temperature and create a suitable living environment for human and biological, we must strengthen the insulation requirements of greenhouse enclosure structure. In modern facility agriculture production, the rigid plastic plate, polyester film and glass are used as the outer protective structure in greenhouse, and the thermal conductivity of these materials is much higher than that of nano aerogel insulation felt. Although radiation heat transfer is the main factor affecting the thermal insulation performance of greenhouse covering materials, convection and conduction are also the causes of heat loss in greenhouse. therefore, the thermal conductivity of covering materials also has a certain effect on the thermal insulation performance of greenhouse. A proper amount of nano aerogel thermal insulation felt can be added into the hard polyester sheet of the greenhouse covering material to prepare a novel composite plate, or a nano aerogel thermal insulation felt coating is appropriately sprayed on the surface of the polyester film, and the nano aerogel thermal insulation felt is used for replacing air as a filling medium in the double-layer hollow glass plate, so that the thermal conductivity of the original greenhouse covering material can be effectively reduced, and the thermal insulation performance of the greenhouse covering material can be improved. The new coating materials doped with nano aerogel thermal insulation felt also have certain resistance to infrared radiation, which can not only reduce the radiation heat transfer in winter, but also shield the light in summer.
The heat preservation and heat storage of solar greenhouse mainly depends on the absorption and accumulation of solar energy by the thick wall in the north, which is composed of heat storage layer, heat insulation layer and heat insulation layer. the wall is usually constructed of heavy materials, and the thickness is usually up to several meters, which not only occupies a large amount of land, but also consumes a large amount of building materials. If that composite wall body is prepare by mixing nano aerogel thermal insulation felt into a novel composite plate to replace hollow brick, aerated concrete building blocks, polystyrene board and the like as the thermal insulation layer material, the thickness of the thick wall thermal insulation lay can be greatly reduced under the condition of ensuring the same thermal insulation effect, so that the land area is effectively saved, the operable space in the greenhouse is increased, the energy source is greatly saved, and the economic benefit is improved.
2, that nano aerogel thermal insulation felt is use as a ground thermal insulation material for facility cultivation
Compared with roof and wall, the heat loss of floor is not big, but the ground is the place where livestock and poultry directly move. the insulation performance of floor will directly affect the growth and development of livestock and poultry, so it is usually necessary to set insulation layer in the ground of livestock and poultry house. Commonly used insulation materials are hollow brick, corrugated tile, aerated concrete or polystyrene and other materials, and these materials compared with nano aerogel insulation felt insulation materials, not only the thermal conductivity is higher, and water absorption is easy to drum deformation after icing, increase the solid heat transfer, its insulation performance will be greatly reduced, and poor mechanical properties. The hydrophobic nano aerogel thermal insulation felt composite plate can be use as a ground thermal insulation material, so that that thermal insulation effect can be improved, and the condition that the thermal insulation performance is reduce due to water absorption and icing can be avoided; and meanwhile, a moisture-proof lay is not needed to be arranged in the ground, so that the construction operation is convenient, the material can be saved, and the production cost can be reduced.
3. application of nano aerogel thermal insulation felt in agricultural building heating system
Heating is the most effective way to control indoor temperature and environment of agricultural buildings in winter. the common heating methods are hot air heating, hot water heating and steam heating, and hot water heating is used most frequently. In the hot water heating system, heat must pass through the conveying pipe to be sent into the greenhouse or livestock and poultry house, and in the process of conveying due to the poor heat preservation performance of the pipe, resulting in a large number of heat loss, not only can not effectively meet the heating requirements of the greenhouse or livestock and poultry house, but also lead to the waste of energy, which is a major problem of heating facilities agriculture in winter. Nano - aerogel as a new type of thermal insulation material has been applied in the oil industry. for example, the thermal insulation effect of nano-aerogel cotton felt wrapped in the water pump room of the first oil production plant in north China oilfield has been significantly improved, resulting in greater economic benefits. The technology can be applied to a heating system pipeline of an agricultural building; because the heating pipeline is usually long and the cost of wrapping the heating system pipeline by using the nano aerogel cotton felt is higher, the nano aerogel cotton felt can be sprayed on the surface of the conveying pipeline after being made into a special coating, so that the heat conductivity of the pipeline is reduced, the heat loss is reduced, the damage caused by pipeline icing to the heating of greenhouses and livestock and poultry houses in winter is avoided, the boiler load is reduced, and energy conservation and emission reduction are realized. In addition to the above application modes, nano aerogel insulation felt particles and powder can be mixed into common mortar to prepare insulation mortar for thick wall insulation of solar greenhouse. Or spraying nano aerogel thermal insulation felt coating on the surface of the cultivation tank for plant liquid cultivation so as to keep the temperature of the nutrient solution and be beneficial to the growth and development of the plant root system. Or that nano aerogel thermal insulation felt can be made into thermal insulation cotton felt which can be use as greenhouse thermal insulation and the like.