Thermal isolation. Thermal Insulation is defined as the ability of materials to oppose the passage of heat by conduction, which is evaluated by the thermal resistance of said materials. The measurement of thermal resistance or, what is the same, of the capacity to thermally insulate, is expressed, in the International System of Units (SI) in m².K / W (square meter and kelvin per watt), considering as thermal insulating material when its coefficient of thermal conductivity: λ is less than λ <0.10 W / m2K measured at 20 ° C (mandatory) or, in the old Technical System, 0.085 kcal / m2. ° C.
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- 1 Characteristics of thermal insulation
- 2 Types of Thermal Insulator
- 3 Thermal insulation of mineral fibers
- 4 Slag Wool / Rock Wool
- 5 Fiberglass
- 6 Ceramic fiber
- 7 Cellular thermal insulation
- 8 Granular Thermal Insulators:
- 9 Importance of Thermal Insulation.
- 10 Sources
Characteristics of thermal insulation
Thermal insulation materials are those that have low thermal conductivity and prevent the loss or gain of heat from a specific equipment (eg oven, boiler, refrigerator, among others), because they are made of basic materials with a low heat transfer coefficient, formed in such a way that resting air cells are trapped, surrounded by solid walls.
Based on these characteristics, thermal insulation primarily represents economy, because by avoiding heat transmission, the passage of energy from one body to another is avoided, due to a difference in temperature between them. Likewise, a thermal insulation represents an investment that will be recovered in a relatively short time, with the energy savings that will be obtained, and with the best efficiency and operation of equipment and machinery. In addition, a thermal insulator represents equipment efficiency, because by avoiding heat losses or gains, the motors of the equipment are prevented from working at a greater capacity than that of the operation.
Types of Thermal Insulator
The classification of thermal insulation is based on its shape and composition, being as follows:
- Mineral fibers
- Granular thermal insulators
- Cellular thermal insulators
Thermal insulation of mineral fibers
Within the fibrous insulating most used are slag wool, of rock , fiber glass and fiber ceramic (refractory), which are processed from the melt of rock, slag or glass, and converted to fiber with a high speed centrifugation procedure, or through drawing dies or the combination of both. The fibers are multidirectionally distributed and finely divide the air gap . They may or may not be linked together, the mineral fibers are divided:
Slag Wool / Rock Wool
It is a thermal insulator made from the melting state of basaltic type rock or similar, foundry slags, materials with a high content of alumina-silicates.
It comes in two forms:
- With mineral oils: Mat with expanded metaland hexagonal fabric. Maximum operating temperature: 650 oC (1,200 oF).
- With organic binders: Half reeds, Rigid and semi-rigid plates. Maximum operating temperature: 650 oC (1,200 oF) and 1,037 oC (oF).
It is a thermal insulator made from the glass melting state. It comes in the following forms:
- With mineral oils: Mat type I, II and III. Maximum operating temperature: 538 oC (1,000 oF).
- With organic binders: Half reeds, Rigid plates, Rolls. Maximum operating temperature: 538 oC (1,000 oF):
Ceramic Fiber, also called refractory ceramic fiber (FCR), is made from silica and fused aluminum oxide and can carry other oxides ( zirconium , iron , magnesium ) in minor amounts. These fibers have a high resistance to the highest temperatures, where the insulation wool (Mineral Wool and Fiberglass) are not effective.
It comes in the following forms:
- Ceramic Fiber Bedspread: 982 oC, 1,260 oC, 1,316 oC, 1,427 oC, at 4, 6 and 8 lb / ft3
- Ceramic Fiber Board: 1,260 0C, 1,316 0C, 1,427 0C, at 14, 16, 20, 28 and 45 lb / ft3
Cellular thermal insulators
Materials made up of tiny individual cells separated from each other. The cellular material can be glass or foamed plastic. The most widely used thermal insulators are: foamed glass, expanded polystyrene , polyurethane , elastomers and polyisocyanurate .
- Flexible, preformed in sheets, rolls, tubes or rectangular units: Plates, half rods, modules, covers for pipes.
- Foaming on site: Spray polyurethane.
Granular thermal insulators:
Materials composed of nodules that contain empty spaces. They are combined with reinforcing fibers with which they achieve rigidity, structure and preform. The most commonly used are: expanded vermiculite, expanded perlite, diatomaceous earth, calcium silicate and sodium silicate.
- Rigids: Blocks, boards and half rods.
Importance of Thermal Insulation.
The need for thermal insulation is justified for four fundamental reasons :
- Save energy, by reducing thermal losses.
- Improve thermal comfort by reducing the temperaturedifference of the interior surfaces and interior environment.
- Suppress condensation phenomena and thereby avoid humidity.
- Improve the environmental environment, by reducing the emission of pollutants associated with power generation.