What is the difference between heat retention and heat insulation?

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Insulation refers to a technical measure taken to reduce the transfer of heat from the internal heat sources of an insulated object to its exterior. To achieve thermal insulation, it is necessary to use materials and structures with special properties; these materials are known as insulating materials, and these structures are known as insulating structures. Heat insulation (also known as thermal insulation) refers to a technical measure adopted to reduce the transfer of heat from external heat sources to the interior of the object that is to be insulated. To achieve heat insulation, it is also necessary to use materials and structures with special properties; these materials are known as heat-insulating materials, and these structures are known as heat-insulating structures. Heat insulation and cold insulation are collectively referred to as thermal insulation. Heat-insulating materials and cold-insulating materials are also collectively known as thermal insulation materials. From the perspective of heat transfer mechanisms, there is a difference between heat retention and heat insulation, yet people often do not make a strict distinction between them, usually referring to both as heat retention. Insulation has a wide range of applications; many industrial pipelines require insulation, as do many buildings. Thermal insulation and cryogenic insulation – Definitions: Measures to reduce the transfer of heat from a system to the environment; measures to reduce the transfer of heat from the environment to the system, as well as the mass transfer of water vapor from outside to the system’s surface. In engineering terms: When the system temperature is higher than ambient temperature; when the system temperature is lower than ambient temperature. Applications: Thermal equipment and pipelines; cryogenic equipment and pipelines. Energy consumption: Primary energy sources (coal, oil, gas) are used to heat the heat transfer medium; secondary energy sources (electricity) are used to produce a cooling medium, resulting in greater energy consumption. Purposes: To maintain the system temperature and prevent thermal burns from external sources; to maintain the system temperature and prevent freezing or condensation caused by external factors. Basic structure: Insulation layer + moisture barrier layer (optional) + protective layer; insulation layer + moisture barrier layer + protective layer. Insulation materials – General definition: Materials with a thermal conductivity of less than 0.2 W/(m·K) at room temperature are generally considered insulation materials. Insulation materials – Strict definition: When used for thermal insulation, the thermal conductivity of such materials and their products must not exceed 0.12 W/(m·K) at an average temperature of up to 623 K (350°C). When used for cryogenic insulation, their thermal conductivity must not exceed 0.064 W/(m·K) at an average temperature of up to 300 K (27°C)