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» Thermal Resistivity Testing
Thermal Resistivity Testing
Thermal resistivity or specific thermal resistance is the ability of a material to impede the flow of heat. Estimation of thermal resistivity is of prime importance while planning engineering projects because heat transfer may take place through soil mass, concrete blocks, stones and bricks. We provide field and lab testing facilities for estimation of thermal resistivity.
Thermal resistance is the property of an object that determines the temperature difference by which an object or a material will resist the flow of heat. It is the reciprocal of thermal conductance and is measured in Kelvin-meter per Watt. Thermal resistivity can be affected by temperature, humidity, composition, time of application, solid matter proportion and voids in the matter. Resistivity is a material-dependent property and depends on the material's ability to stop the flow of heat through it.
Thermal Resistivity of soil:
Many engineering projects such as underground high voltage power cables, oil and gas pipe lines, ground modification via heating-freezing, nuclear waste disposal and soil shrinkage requires estimation of soil thermal resistivity. Thermal resistivity of field soil is measured in pits or boreholes or under laboratory conditions.
We estimate thermal resistivity of soil depending on various parameters such as soil type, distribution of particle size, and compactness. Naturally soil contains different size fractions of particles ranging from clay to gravel.
Thermal resistivity of soil plays a significant role to electrical power engineering because huge damages are caused to cables due to resistance to flow of heat between cable and surrounding soil.
Thermal resistivity of Cable Insulation:
The thermal resistivity of winding and its insulation is the most critical parameter of an electrical machine thermal analysis. The material used for insulation of wires should have high thermal resistivity and low thermal conductivity. This means that the insulating material should resist the flow of electric current outside.
The insulation of a wire is tested for its resistance to leakage of electric current to prevent melting of the insulation material. The insulation preserves the integrity of wire by providing protection against environmental factors such as water and heat. Materials commonly used as insulation include plastics, rubbers and fluoropolymers.
Thermal Resistivity of concrete walls and blocks:
The efficiency of a building is closely-dependent on the thermal performance of the building materials used. False ceiling made of Autoclaved Aerated Concrete (AAC) have high thermal resistance to avoid transfer of heat from wiring over it into the room. This generates a twin climate chamber with two different environments, one is hot and the other one is cold depending on the temperature and relative humidity.
AAC is used for external walls as it have low density, voluminous character, well-distributed thermal insulation, better durability, higher building speed and better water vapour permeability. They comes in different sizes and strengths and are three times lighter than red bricks.
Thermal Resistivity of ceramic :
The interface temperature is responsible for the localized discomforting sensation while walking barefoot on a hot or cold floor. Ceramic has more pores as compared to glass, so thermal resisitivity of materials made from ceramic is comparitively higher. Ceramic is used to make floor, tiles, mugs, brake disks, knife blades, ball bearings, gas turbine engines
Zirconia blocks and coatings have high thermal resistivity and are used for kiln walls. They prevent leakages of high temperature gases from chambers intended for heating purpose. Zirconia coating should resist temperature upto 1800°C. Zirconia is also used in refractory products, colours and pigments of ceramic, electronics, welding rods etc.
Thermal Resistivity of Glass Wool:
Glass wool is a good thermal insulator and is made up of interwined flexible fibres of glass. Glass wool has high thermal resistivity due to numerous trapped air pockets within the fibres. It is used in cavity wall insulation, curtain walls, ceiling tiles, and ducting in the form of spray, sheets and panels. We test glass wool for their specific heat, thermal resistivity and conductivity to develop insulation with suitable precision.