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What is Thermal Insulation?


Insulation is defined as a material or combination of materials which retard the flow of heat. The materials can be adapted to any size, shape or surface. A variety of finishes are used to protect the insulation from mechanical and environmental damage, and to enhance appearance.

Where is Mechanical Thermal and Acoustical Insulation Installed?

Mechanical thermal insulations are materials that insulate the components of mechanical systems in commercial buildings and industrial processes. In buildings such as shopping centers, schools, hospitals, and hotels, mechanical insulations are installed to improve the energy consumption of the buildings' cooling and heating systems, domestic hot and chilled water supply, and refrigerated systems including ducts and housings.

For industrial facilities, such as power plants, refineries, ethanol plants, and paper mills, mechanical thermal insulations are installed to control heat gain or heat loss on process piping and equipment, steam and condensate distribution systems, boilers, smoke stacks, bag houses and precipitators, and storage tanks.

Functions of Insulation

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.
•Assist mechanical systems in meeting USDA (FDA) criteria in food and pharmaceutical plants.
•Reduce noise from mechanical systems.

Understanding Heat Flow/Heat Transfer

In order to understand how insulation works, it is important to understand the concept of heat flow or heat transfer. In general, heat always flows from warmer to cooler surfaces. This flow does not stop until the temperature in the two surfaces is equal. Heat is 'transferred' by three different means: conduction, convection and radiation. Insulation reduces the transference of heat.

Conduction

Conduction is direct heat flow through solids. It results from the physical contact of one object with another. Heat is transmitted by molecular motion. Molecules transmit their energy to adjoining molecules of lesser heat content, whose motion is thereby increased. For example, when people first sit down on cold metal chairs, they instantly feel the discomfort that comes from the contact of a warm body with a cold chair as body heat is quickly transferred from the skin, and through clothing, to the chair by conduction.

Convection

Convection is the flow of heat (forced and natural) within a fluid. A fluid is a substance that may be either a gas or a liquid. The movement of a heat- carrying fluid occurs either by natural convection or by forced convection as in the case of a forced-air furnace. For example, people usually detect a draft when standing close to a single glazed window in the winter. Air within the room tends to stratify so that the air near the ceiling is warmer because it has become less dense when heated and so it rises. This is natural convection. That warm air loses heat to the vertical window because heat flows from hot to cold. This air becomes cooler and denser, so it begins to sink. This is the draft felt by people and is another example of natural convection. Warm air entering a room from a supply duct is an example of forced convection.

Radiation

Radiation is the transmission of energy through space by means of electromagnetic waves. Radiated heat moves at the speed of light through the air without heating the space between the surfaces. An example is the warmth you feel on your skin from the sun. The sun is unbelievable hot, and the space between it and us is still unbelievable cold.

How Insulation Works

The basic requirement for thermal insulation is to provide a significant resistance path to the flow of heat through the insulation material. To accomplish this, the insulation material must reduce the rate of heat transfer by conduction, convection, radiation, or any combination of these mechanisms.