a material with a low thermal conductivity that is used in refrigerating engineering to insulate the structures—for example, walls, housings, and floors—that enclose refrigerator compartments or other objects to be cooled and to insulate the low-temperature equipment and piping of refrigerating systems. The purpose of low-temperature insulation is to reduce both the heat leakage from the environment and the loss of cold.
Materials used as low-temperature insulation have a thermal conductivity λ = 0.035–0.14 watts/m°K and a density ρ = 25–300 kg/m3. Such materials should also be, for example, chemically inert with respect to materials with which they are in contact, odorless (of great importance for the storage of food products), frost-resistant, noncumbustible, and resistant to penetration by rodents and to the action of fungi and microorganisms.
For the convenience of users, industry produces insulating materials in various forms, such as boards, blocks, blankets, strips, and preformed sections. A widely used method of insulation is the pouring or spraying of two liquid compounds that foam and harden when mixed. The compounds either are poured between the walls of the structures that enclose an object to be insulated or are sprayed on a surface to be insulated.
Both organic and inorganic materials are used as low-temperature insulation. The organic materials include polystyrene foam and polyurethane foam; examples of the inorganic materials are foam glass and mineral-wool boards. Since moisture reduces the effectiveness of low-temperature insulation, such insulation is usually coated with a waterproofing agent, for example, a bitumen, a bituminous mastic, ruberoid, or a polymer film.
REFERENCESpravochnik po spetsial’nym rabotam: Teplovaia izoliatsiia, 2nd ed. Moscow, 1973.
V. V. VASIUTOVICH