1. Purpose of Insulation
2. Fundamentals of Heat Transfer
• Convection : The transfer of heat by the movement of parts of a fluid within the fluid , because of difference in the density, due to the difference in the temperature of the parts of the fluid.
• Radiation: The transfer of heat energy from a high temperature body, through space, to another lower temperature body.
3. Thermal Conductivity
4. First Law of Thermodynamics
5. Second Law of Thermodynamics
7. Conductive Heat Transfer
Or Q = - kA. dt /dx
8. Convective Heat Transfer
Properties of Thermal Conductivity
2. It depends on structure and other physical properties.
3. It depends upon temperature.
9. Conductivity through Thick Plane Homogeneous Wall
2. Thermal conductivity remains constant.
3. No heat flow takes place along y or z axes.
varying with temperature :
α = +ve for insulating material
= - ve for conductive material
10. Conductance through a Flat Composite Wall
11. Thermal Conductivity of Various Materials at 0 deg C
• For gases and insulating material, it increases with rise in temperature.
12. Heat Conduction through Hollow Cylinder
be written as
13. Heat Transfer through Composite Cylinder
14. Grouping of Insulation Requirements
15. Various forms of Insulation Material
3. Moulded blocks
16. Physical Properties of Insulating Material
2. Compressive strength
5. Moisture absorption
7. Effect of temperature
9. Ease of application
17. Properties of Some Common Insulating Material
3. Refractor y / Ceramic : Good for ver y high temperature, high compressive strength, no moisture absorption.
18. Method of Application of Insulating Material
Typical insulation system on a vertical cold room wall:
2. Bitumen layer
3. Vapour barrier
4. Wooden batten
5. Insulation slab - EPS
6. Bitumen seal coat
7. Wire netting
8. Sand/ cement plaster
Typical insulation system on a hot pipe
19. Design Parameters for Insulation System
2. Providing personal protection
3. Providing personal comfort in commercial building
4. Reducing heat gain by cold piping
5. Reducing surface condensation
6. Economic optimisation of energy conservation
3. Density of glass wool : 80 – 100 Kg/m3
4. Surface temperature after insulation = 55 – 60 deg C
5. Insulation upto 65 mm- single layer, otherwise two layers.
20. Specific Weight and Conductivity of Materials
Selection of insulating material:
1. Select design criteria
2. Specify inside/outside temperature
3. Specify insulation material
4. Find optimum insulation thickness
5. Specify application techniques
6. Finalise complete insulation system
21. Insulation Specification Sheet
2. In the given condition find :
c) Hourly heat loss
To calculate interface temp:
1. The purpose of insulation is to maintain process conditions.
2. The US practice of deciding insulation thickness for personnel protection on the basis of surface after insulation is not more than 520C.
3. Conduction is transfer of heat energy due to difference in density.
4. Second law of thermodynamics: It is possible to construct a device that operates in a cycle and converts all amount of heat into work, while exchanging heat with a single source.
5. Velocity of fluid layer at the wall is maximum.
6. Thermal Conductivity is the physical property of a substance and characterises the ability to transfer heat.
7. Dependence of thermal conductivity on temperature is non-linear.
8. Conductivity for most pure metals decreases with increasing temperature.
9. For gases and insulating material, conductivity increases with rise in temperature.
10. Hot insulation material examples : Expanded polystyrene (EPS), Polyurethane Foam (PUF).