Insulation is used to perform one or more of the following functions:
• Reduce heat loss or heat gain to achieve energy conservation.
• Protect the environment through the reduction of CO2, NOx,, and greenhouse gases.
• Control surface temperatures for personnel and equipment protection.
• Control the temperature of commercial and industrial processes.
• Prevent or reduce condensation on surfaces.
• Increase operating efficiency of heating/ventilation/cooling, plumbing, steam, process, and power systems.
• Prevent or reduce damage to equipment from exposure to fire or corrosive atmospheres.
• Reduce noise from mechanical systems.
Other than the application of insulation, the selection aspects of the insulation material are also
• Very important. The following design and installation considerations must be noted:
• Type of insulation – rigid, flexible, ease of handling, installation, and adjustment.
• Ease to modify, repair, and alter.
• Requirement of skilled and unskilled labor.
• Safety & environment considerations.
• Weight and density of insulation material.
• Ease of removal and replacement.
• Type of vapor retarder and insulation finishes.
• Thermal performance.
4.6.2 Heat Gain / Loss from Cylindrical Surfaces like Pipes
Unlike flat surfaces, the inner and outer surface areas for pipes are different and therefore the heat transfer equation is different. The pipe wall surface will gain heat directly by conduction from the fluid flowing through it. The heat is then dissipated to the atmosphere, or it flows at a restricted rate through the insulation if the pipe is insulated. The exact rate of heat loss is very
Complicated to calculate on a theoretical basis alone, 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 based upon the equivalent thickness of insulation and the area of outer surface of insulation.