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Before dealing with the principles of insulation it is necessary to have an understanding of heat transfer. When a hot surface is surrounded by an area that is colder, heat will be transferred from hot to cold surface & process will continue until both surfaces are at the same temperature. The heat transfer takes place by one or more of three methods - Conduction, convection & radiation.
Thermal Insulation is a barrier that minimizes the transfer of heat energy from one materials to another by reducing conduction, convection and/or radiation effect.
Insulation cannot stop heat energy from flowing but it can only reduce the rate of heat flow. |
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| Insulation is required for following purposes |
- To reduce heat loss
- To reduce running cost
- To control process temperature
- To control surface temperature
- To reduce heating plant capacity
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| Proper insulations make the heating process more energy efficient & also provides good working environment to operators. |
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| Criteria for selecting thermal insulation |
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Most Insulation is used to prevent the conduction of heat. In some cases, radiation is a factor. A good insulator is obviously a poor conductor.
Less dense materials are better insulators, the denser the material; the closer it’s atoms. That means the Transfer of energy of one atom to the next is more effective. Thus gases insulate better than liquids, which in turn insulate better than solids.
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| The properties of good thermal insulation are |
- Low thermal conductivity
- Low density
- High Specific heat
- Appropriate Mechanical Strength
- Capability to withstand enviornment
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