Thermal conductivity is an ability of material to transmit heat and it is measured in Watts per meter- kelvin of surface area for a temperature gradient of 1K per unit thickness of 1m. It is denoted by k, λ, or κ). Transfer of Heat is comparatively slower across materials of low thermal conductivity whereas higher in materials with high thermal conductivity. Hence, the application of this material varies with its conductivity; for example, materials with high conductivity are preferably used as heat sink and for thermal insulation, material with low thermal conductivity is considered. There are certain factors affecting the thermal resistivity (reciprocal of thermal conductivity) such as temperature, humidity, composition, application time, proportion of solid matter or the voids of the materials. Correspondingly, the application of thermal conductivity or resistivity has its own significance to ensure the appropriate utilization of the materials. Similarly, when it comes to your house, office or any other building, thermal insulation plays a pivotal role.
Sigma Test & Research Centre provides the test facility of thermal conductivity in building materials which include powdered as well as dense matter.
Thermal conductivity of soil is associated with the transfer of heat through the soil by conduction. Soil's thermal conductivity is influenced by its saturation and dry density. An increase in saturation or dry density of a soil will result in an increase in its thermal conductivity as it affects the temperature, texture, mineral composition and time.
Soil thermal resistivity becomes interestingly important for electrical power engineers, because resistance to heat flow between the cable and the ambient environment causes the cable temperature to rise. Catastrophic failure may occur when cable temperature becomes too high. Sigma Test & Research Centre provides through its dedicated team of electrical professional onsite soil thermal resistivity and soil thermal conductivity measurement for solar projects, power projects, Railways, SEZ's across India.
The Autoclaved aerated concrete Blocks (AAC Blocks) are used in building construction for external walls. Due to the low density and its voluminous aspect, efficiency of a building depends on the thermal conductivity of the block. As per the climatic conditions and its favourable water vapour permeability, the peculiarities of the building lie within the AAC block's annual heating energy consumption upto 75kW.h/m2/year. Hence, the main objective is to design the type of building which decrease the residential energy consumption and raise the efficiency of the building of low thermal conductivity (lower than 0.1 W/m.K) or very thick thermal insulations.
To provide the thermal insulation between building industry and air, the fiber materials such as glass wool fiber is used to determine its thermal properties. The specific heat, thermal diffusivity and thermal conductivity are such parameters which need to be known with suitable precision to develop insulation. There are certain processes which include thermal table method and thermal flow indicator. Based on the data of evaluation of periodical changes of heat, the thermal conductivity is found.
Products under this category are Natural stones, granite, porcelain stoneware and red stoneware materials are used as floor decorations. The materials used for floor must be of lower effusivity for efficient floor work. Thermal effusivity is corresponds to material density and thermal conductivity. More the thermal conductivity, lower the water absorption such as white stoneware and vinyl, having thermal conductivities below 1 W m−1 K−1.
Depending on the interface temperature, the contact resistance, highly dependent of the crustiness surface plays important role to calculate the thermal conductivity.