Thermal insulation refers to the many ways we attempt to inhibit the transfer of heat from one object to another. These two objects may be the hot and cold faces of processing equipment in industrial facilities or the interior and exterior of external walls in domestic properties.
The contexts in which thermal insulation may be used are theoretically limitless. Despite the vast range of applications available to functionalized insulating materials, they all provide similar fundamental benefits: Lower energy losses lead to greater efficiency which yields greater returns on investment ROIs.
Whether insulating residential cavity walls or shielding sensitive mechanics from high temperatures, all different types of insulation abide by these same simple principles. In this article, Mid-Mountain Materials, Inc.
Before outlining the various types of insulating materials used in high-temperature applications, it is worth reviewing some of the basic concepts of thermal conduction and insulation.
Heat is a thermodynamic quantity of thermal energy that flows from one system to another when there is a temperature differential between the two.
It is transferred via one of three different methods:. Thermal insulation is typically used to limit heat transfer via conduction which requires objects to be in direct contact with one another. Some types of insulation utilize reflective coatings to prevent heat transfer via radiation, but in this article, we are mainly dealing with heat transfer between contacting objects.
The rate at which heat transfers between objects is determined by the thermal conductivity k of materials. Metals and ceramics with high thermal conductivities are often used for heat transfer applications. Vice versa, low thermal conductivities yield extremely high resistance values.
The science of embodied carbon is still evolving - consequently, firm and reliable data is difficult to obtain. Look out for EPDs which detail the inputs and outputs of the industrial processes. Read more It is measured by the time rate of vapour transmission through a unit area of flat material of unit thickness induced by a unit vapour pressure difference between two specific surfaces,under specified temperature and humidity conditions.
Often referred to, erroneously, as 'Breathing construction', walls and roofs so termed are characterised by their capacity to transfer water vapour from the inside to the outside of the building - so reducing the risk of condensation. Gases possess poor thermal conduction properties compared to liquids and solids, and so makes a good insulation material if they can be trapped. In order to further augment the effectiveness of a gas such as air it may be disrupted into small cells which cannot effectively transfer heat by natural convection.
Convection involves a larger bulk flow of gas driven by buoyancy and temperature differences, and it does not work well in small cells where there is little density difference to drive it.
In foam materials small gas cells or bubbles occur within the structure; in fabric insulation, such as wool, small variable pockets of air occur naturally to form gas cells. Industrially produced wood fibre insulation was introduced around twenty years ago after engineers from the timber producing areas of Europe devised new ways of transforming timber waste from thinnings and factories into insulation boarding.
Cellulose insulation is a material made from recycled newspaper. The paper is shredded and inorganic salts, such as boric acid, are added for resistance to fire, mould, insects and vermin. The insulation is installed either blown or damp-sprayed depending on application. Sheep are no longer farmed primarily for their wool; however, they need to be clipped annually to protect the health of the animal. The wool used to manufacture insulation is the wool discarded as waste by other industries due to its colour or grade.
Hemp fibres are produced from hemp straw of the hemp plant. Most hemp is imported, but an increasing amount of home-grown crop is becoming available. Hemp grows up to a height of nearly 4 metres within a period of days.
Because the plants shade the soil, no chemical protection or toxic additives are required for hemp cultivation. Hempcrete is a mixture of hemp hurds shives and lime possibly including natural hydraulic lime, sand, pozzolans or cement used as a material for construction and insulation. Hempcrete is easier to work with than traditional lime mixes and acts as an insulator and moisture regulator. It lacks the brittleness of concrete and consequently does not need expansion joints.
Largely manufactured from recycled glass e. The powdered glass is poured into molds and heated below the melting point in a "sintering" process that causes the particles to adhere to one another. Next, a small amount of finely ground carbon-black is added and the material is heated in a "cellulation" process.
Here, the carbon reacts with oxygen, creating carbon dioxide, which creates the insulating bubbles in the material. Straw is an agricultural by-product, the dry stalks of cereal plants, after the grain and chaff have been removed.
Straw makes up about half of the yield of cereal crops such asbarley, oats, rice, rye and wheat. The material is formed from fibres of glass arranged using a binder into a texture similar to wool. The process traps many small pockets of air between the glass, and these small air pockets result in high thermal insulation properties. The density of the material can be varied through pressure and binder content.
More advanced production techniques are based on spinning molten rock in high-speed spinning heads somewhat like the process used to produce candy floss. Cellulose is made from recycled cardboard, paper, and other similar materials and comes in loose form. Cellulose has an R-value between R Some recent studies on cellulose have shown that it might be an excellent product for use in minimizing fire damage.
Because of the compactness of the material, cellulose contains next to no oxygen within it. Without oxygen within the material, this helps to minimize the amount of damage that a fire can cause. So not only is cellulose perhaps one of the most eco-friendly forms of insulation, but it is also one of the most fire resistant forms of insulation.
However, there are certain downsides to this material as well, such as the allergies that some people may have to newspaper dust. Also, finding individuals skilled in using this type of insulation is relatively hard compared to, say, fiberglass. Still, cellulose is a cheap and effective means of insulating. While not the most abundant of insulations, polyurethane foams are an excellent form of insulation. Nowadays, polyurethane foams use non-chlorofluorocarbon CFC gas for use as a blowing agent.
This helps to decrease the amount of damage to the ozone layer. They have an R-value of approximately R There are also low density foams that can be sprayed into areas that have no insulation.
These types of polyurethane insulation tend to have approximately R Another advantage of this type of insulation is that it is fire resistant. Polystyrene is a waterproof thermoplastic foam which is an excellent sound and temperature insulation material. The two types differ in performance ratings and cost. Polystyrene insulation has a uniquely smooth surface which no other type of insulation possesses.
Typically the foam is created or cut into blocks, ideal for wall insulation. The foam is flammable and needs to be coated in a fireproofing chemical called Hexabromocyclododecane HBCD. HBCD has been brought under fire recently for health and environmental risks associated with its use. Although the items listed above are the most common insulation materials, they are not the only ones used. Recently, materials like aerogel used by NASA for the construction of heat resistant tiles, capable of withstanding heat up to approximately degrees Fahrenheit with little or no heat transfer , have become affordable and available.
One in particular is Pyrogel XT. Pyrogel is one of the most efficient industrial insulations in the world. Although a little more expensive than some of the other insulation materials, Pyrogel is being used more and more for specific applications.
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