Distinction between heat retention, cold retention, and insulation concepts

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Insulation of low-temperature equipment and pipelines is referred to as cold insulation, while insulation of thermal equipment and pipelines is called heat insulation; together, these two concepts are known as thermal insulation in engineering. Generally, it is classified according to the temperature of the medium stored and transported in equipment and pipelines; insulation measures for media with temperatures below room temperature are referred to as cooling insulation, while those for media with temperatures above room temperature are called heating insulation. Insulation is a measure that utilizes insulating structures made of engineering materials with special properties to reduce heat flow resulting from temperature differences between the inside and outside of the structure. The purpose of insulation is to meet the requirements of production processes, and to maintain and optimize production capacity ； Reduce cold (heat) losses and save energy ； As well as preventing surface condensation or burns, and improving the working environment. Therefore, heat insulation and thermal protection, both belonging to the field of thermal engineering, share essentially the same thermal insulation principles, the same thermal insulation structures and measures, as well as the same objectives. *It is common to refer to both heat insulation and cold insulation as thermal insulation. Thermal insulation differs from heat retention in three main aspects: first, the direction of heat transfer is opposite; thermal insulation involves heat transfer from the outside to the inside, while heat retention involves heat transfer from the inside to the outside. Therefore, thermal insulation systems are affected not only by the inward transfer of heat from the outside but also by the penetration of water vapor contained in the moist air in the external environment ； Secondly, regarding the structure used for insulation, in order to prevent external water vapor from penetrating inward, a moisture barrier layer needs to be applied outside the insulation layer ； Thirdly, thermal insulation media commonly use primary energy sources (such as coal and oil), while cooling media typically utilize secondary energy sources (steam) or secondary energy sources (electricity). Due to equipment depreciation and the losses associated with multiple energy conversions, the cost of cooling is generally 4–6 times higher than that of heating; therefore, reducing unit cooling losses carries a greater economic value in terms of energy savings. Insulating material is a lightweight material with excellent insulating properties. In engineering, materials with a thermal conductivity of less than 0.2 W/(m·K) at room temperature are generally referred to as insulating materials. As for the insulation of equipment and pipelines, stricter requirements have been established: when used for insulation purposes, the thermal conductivity of the insulating materials and products must not exceed 0.12 W/(m·K) at an average temperature of 623 K (350°C) or less ； When used for thermal insulation, the thermal conductivity value of their insulating materials and products must not exceed 0.064 W/(m·K) at an average temperature of 300 K (27°C) or less.