Thermal conductivity testing is the ability of a 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.
Heat transfer is comparatively slower across materials with 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 a heat sink and for thermal insulation, a material with low thermal conductivity testing is considered.
There are certain factors affecting the thermal resistivity (reciprocal of thermal conductivity) such as temperature, humidity, composition, application time, the proportion of solid matter, or the voids in materials.
Correspondingly, the application of thermal conductivity or resistivity has its own significance, to ensure the appropriate utilization of materials. Similarly, when it comes to your house, office, or any other building, thermal insulation plays a pivotal role.
All Lab provides the test facility of thermal conductivity in building materials which include powdered as well as dense matter.
Thermal Conductivity Testing In Soil
The 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 the 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 the cable temperature becomes too high. Sigma Test & Research Centre provides through its dedicated team of electrical professionals, onsite soil thermal resistivity and soil thermal conductivity measurement for solar projects, power projects, Railways, SEZs across India.
Thermal Conductivity Testing In AAC Block
Autoclaved Aerated Concrete Blocks (AAC Blocks) are used in the construction of external walls of buildings. Due to the low density and voluminous aspect, the efficiency of a building depends on the thermal conductivity of the block.
As per the climatic conditions and its favorable water vapor permeability, the peculiarities of the building lie within the AAC block’s annual heating energy consumption up to 75kW.h/m2/year.
Hence, the main objective is to design the type of building that decreases the residential energy consumption and raises the efficiency of the building of low thermal conductivity (lower than 0.1 W/m.K) or very thick thermal insulation.
Thermal Conductivity Testing In Glass Wool
To provide thermal insulation between the building industry and air, the fiber materials such as glass wool fiber is used to determine their thermal properties.
The specific heat, thermal diffusion, and thermal conductivity are parameters that need to be known with suitable precision to develop insulation.
There are certain processes that include a thermal table method and a thermal flow indicator. Based on the evaluated data of periodical changes of heat, the thermal conductivity is determined.
Thermal Conductivity Testing In Stones And Tiles
Products under this category are Natural stones, granite, porcelain stoneware, and red stoneware materials that are used as floor decorations. The materials used for the floor must be of lower thermal effusivity for effective floor performance.
Thermal effusivity corresponds to material density and thermal conductivity. More 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, which is highly dependent on the crustiness surface, plays an important role to calculate the thermal conductivity.
What is thermal conductivity testing?
Thermal conductivity is a material property that explains the intrinsic ability of a material to conduct or transfer heat. It is measured in watts per Kelvin (K).
Why is thermal conductivity important?
Thermal conductivity testing is important for applications where the temperature is required to be intemperate quickly and others where the temperature needs to be slower or maintained.
How thermal conductivity of a material is tested or measured?
There are various options suitable depending on temperature and thermal properties
Guarded Heat Flow (GHP)
Heat Flow Meter (HFM)
Transient Hot Wire (THW)
Laser Flash Diffusivity
Which materials are tested using thermal conductivity?
Ceramics
Metals, metal alloys and non-metals
Concrete, asphalt, and firebricks
Soil and environmental products
Glass wool
Powders and powder mixtures
Stones and tiles
Plastic and polymers
Insulating products
Liquids, Liquid mixtures, and Nanofluids
Material with the highest thermal conductivity is Diamond (2000-2200 W/m.K)
Material with the lowest thermal conductivity is Aerogel (1.3-1.4 W/m.K)
What are the set standards for thermal conductivity testing?
Indian Standard for testing thermal conductivity is IS 9489: 1980