Function of insulation are:
• To conserve energy to avoid heat loss or heat gain
• To control and maintain surface temperature of vessel
• To reduce condensation
• To avoid corrosion or exposure to corrosive atmosphere as well as fire
• Improve efficiency of processes like ventilation, plumbing, heating, steam and power system.
• To maintain and control temperature of industrial processes
• To absorb noise from the mechanical equipment.
Selection of insulation material is very critical and following points should be considered.
Very important. The following design and installation considerations must be noted:
• Type of insulation that is rigid, flexible, ease of handling, installation, and adjustment.
• Ease to modify, repair, and alter.
• Requirement of skilled and unskilled labor.
• Safety & environment considerations.
• Weight of insulation material and density of same
• Replacement and removal should be easy
• Type of vapor retarder and insulation finishes.
• Performance of material.
4.6.2 Heat Gain / Loss from Cylindrical Surfaces like Pipes
To evaluate the heat gain or loss from the cylindrical surfaces it has different equation from than the equation for the flat surfaces. The heat will be transferred to pipe wall through the flowing material and after that heat will be absorbed by the atmosphere. In case of insulation the heat dissipation will be less in atmosphere.
It is not possible to calculate exact amount of heat dissipated since it is affected by:
• Color, texture, and shape of the casing.
• Vertical or horizontal orientation of the casing.
• Air movement or wind speed over the casing.
• Exposure to thermal radiation, e.g. sunlight – all of these in addition to the temperature
• Parameters, etc.
Because of the number of complicating factors, generalizations must be utilized. The theoretical methods for calculating heat transfer for pipe or any other cylindrical objects like tanks, is depends on the equivalent insulation thickness and the area of outer surface.