Heat Insulating Materials: Convection, Radiation, and Conduction

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Heat Insulating Materials

The purpose of thermal insulation is to restrict the heat transfer from warmer to cooler areas. Transfer of heat takes place by three processes- the convection, the radiation and, the conduction.

Convection

In convection, heat is transferred from one place to another by the movement and mixing of liquids or gases.

Radiation

Radiation is the process of transferring heat in a similar manner to that in which light is transmitted, i.e., by means of invisible wave radiation. The extent to which a building material radiates heat is mainly dependent on the emissivity of the surface, on the temperature of the surface, and on the temperature of the surrounding surfaces; metals have very low emissivities.

Conduction

Conduction is a process whereby heat is passed on between adjacent stationary particles of matter. The conductivity of building materials depends upon their density and porosity, and upon their content. Since bulk densities of materials vary inversely to their air contents, those materials which enclose a high proportion of air in their structure are generally better heat insulators.

Heat Insulating Materials: Convection, Radiation, and Conduction

Water is a good heat conductor, if present in the material, makes the material a poor insulator.

The commonly used heat-insulating materials work on the principle of either air spaces formed between structural components, surface insulation, or internal insulation.

Well Known Products of Heat Insulation

  1. Aerated concrete
  2. Gypsum boards
  3. Fibre boards
  4. Asbestos cement boards
  5. Chipboards
  6. Corkboards
  7. Foam plastic
  8. Aluminium foil
  9. Reflecting paints
  10. Expanded blast furnace slag
  11. Vermiculate*
  12. Fibreglass
  13. Glass wool
  14. Cavity wall, though costly

Properties of Heat Insulating Materials

Heat insulating materials should be impermeable to water, fireproof, resistance to insect attacks, have low thermal conductivity (0.0228 kCals-cm/m2oC). Since a good heat insulating material has a porous structure the strength is lowered affecting the stability.

Also Read-

Rigid Pavements: Objective, Advantage, Disadvantage, Components, and Affecting Factors
Flexible Pavements: Objective, Advantage, Disadvantage, Components, and Affecting Factors
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Types of Joints in Rigid Pavements: Longitudinal and Transverse

Joints are too important for the rigid pavements because the joints are responsible for reducing stresses developed due to temperature variations. There are two type of joints-

  • Longitudinal Joints
  • Transverse Joints

The Transverse joints are subdivided into three categories-

  • Expansion Joints
  • Contraction Joints
  • Construction Joints

Continue Reading Types of Joints in Rigid Pavements: Longitudinal and Transverse

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2 Comments

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