Thermal Insulation
Thermal insulation is used in HVAC to avoided heat loss or heat gain from the duct of pipe.
It also avoids condensation on cold surfaces.
A heat-insulating material is one which has low thermal conductivity.
Eg.
1. Duct carries chilled air from the AC unit to space, Heat loss or gain can change the temperature of the air
To avoid heat loss or gain, thermal insulation is used
2. Pipe
Chilled water pipe carrying water or refrigerant from one unit to other
to avoid Heat loss or gain, thermal insulation is used.
Steam is generated in boiler and it is taken to the turbine through the pipe.
To reduce heat loss or gain, insulation is used.
Required Property on Insulating material
1. Can withstand high or low temperature
2. Should have a long life and can not be easily damaged.
3. Easy to install.
4.Should be economical.
5.Fire resistance.
6. resistance to Ozone and UV.
Various material such as asbestos, glass wool, expanded polystyrene, puff, nitrile material is used for thermal insulation.
Effectiveness of material is measured on basis of the coefficient of thermal conductivity.
It is represented by 'K'.
It is defined as the ability of a substance to conduct heat.
Formula
Q =Heat transfer
A=Area of heat flow normal to the direction of flow
L = Thickness of material
Delta T is temperature difference
Thermal conductivity of some material commonly used
Material Used For Insulation
-Nitrile Rubber
-Mineral wool
-Fibreglass
-Armasound
-Puff (Polyeurothene foam)
-EPS(Polystyrene)
-XLPE
Nitrile rubber of different thickness can be used over ducts, chilled water pipe.
Nowadays it is most commonly used as its installation is very easy. It is available as an open cell as well as closed-cell.
Closed-cell is used for thermal application and open-cell(Armasound) used as thermal and acoustic purpose.
Puff material is used over ducts and pipe. It reduces sound as well as heat transfer.
For pipe, it is available in the section. Nowadays it is also used for under deck application due to its thermal property.
EPS is waterproof thermoplastic foam.It is available in two types i.e. extruded type and expanded type.
It is mostly used for pipe insulation and underdeck application due to its less weight.
Fibreglass or glass wool is a man-made fibre made of finely woven silicon, glass powder, and tiny shards of glass. It was most commonly used insulation but nowadays its use is very limited because of its handling. As it is made of the very tiny particle so, it can damage the eye, lungs and skin.
This is why it is not used in the pharma industry.
Mineral wool is mostly called as glass wool which is fibreglass made of recycled glass.
it is also called rock wool which is made of basalt.it is also called as slag wool as it is made of the steel mill. It is used for thermal as well as acoustic purpose.
Cross-linked polyethylene commonly knows as XLPE or PEX or XPE.
It is used for thermal application in HVAC as well as the electrical industry. Its main advantages are its low weight and less cost.
All the insulation is covered by AL or GI cladding when it is used for outdoor application. Some times glass cloth with a lag coating used to protect it.
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