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INSULATION
Insulation materials are products that have the ability to reduce heat transfer between objects exposed to heat or within the range of radiation influence. Thermal insulation can be achieved by specially designed methods or processes, as well as with appropriate shapes and materials.
Definition of Insulation Material:
Insulation material is a product with the ability to reduce heat transfer (meaning the transfer of thermal energy between objects at different temperatures) between objects in contact with heat or within the range of radiation influence. Insulation can be achieved through specifically designed methods or processes, as well as with appropriate forms and materials.
INSULATION
Heat flow is an inherent result of contact between objects with different temperatures. Insulation provides a thermal barrier where heat conduction is reduced, or heat radiation is reflected rather than absorbed by a body with a lower temperature.
The insulation capability of a material is measured by the inverse of thermal conductivity (\(k\)). Low thermal conductivity is equivalent to high insulation ability (high electrical resistance). In thermal engineering, other important properties of insulation materials include density (\(\rho\)) and specific heat capacity (\(c\)).
Thermal Conductivity:
Thermal conductivity (\(k\)) is measured in watts per meter per kelvin (W·m⁻¹·K⁻¹ or W/m/K). This is due to heat transfer, measured by power, being found (approximately) to be proportional to:
- The temperature difference.
- The surface area in contact with heat (\(A\)).
- The inverse of the material thickness (\(d\)).
From this, the power of heat loss (\(P\)) can be given by:
\[ P \propto \frac{\Delta T \cdot A}{d} \]
Thermal conductivity depends on the material and, for liquids, its temperature and pressure. For comparison purposes, electrical conductivity under standard conditions (20°C at 1 atm) is often used. For some materials, thermal conductivity may also depend on the direction of heat transfer.
Additional Information:
Insulating action is achieved by wrapping an object with a material having low thermal conductivity and high thickness. Reducing the surface area in contact can also decrease heat transfer, but this quantity is often determined by the shape of the object requiring insulation.
Multilayer insulation materials are used when radiation loss is predominant or when users are constrained by the volume and weight of insulation materials (e.g., emergency blankets, radiation shields).
Additional note: For a list of insulation materials, refer to: [List of Insulation Materials](link to the list).
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