W/mK is the Unit for Thermal Conductivity

What is W/mK

Thermal conductivity (k) measures a material’s ability to conduct heat by conduction. It gives an idea of how quickly and efficiently heat can pass through a given material. W/mK or watts per meter kelvin is the unit that measures the heat transfer rate across a material. A value of 1 W/mK depicts the heat transferred through a thickness of one meter of the given material across the temperature difference of one kelvin. A higher value of W/mK means heat travels through the material more easily. This information is required to design objects that need to manage heat, such as electronics, automobiles, utensils, buildings, and many more.

Measurement of Thermal Conductivity

Measuring a raw material’s thermal conductivity (k) is required for material selection, quality control, and design optimization across various industries. Many flexible methods and techniques exist for measuring thermal conductivity (W/mK) because, unlike other physical properties, thermal conductivity is dependent on many factors, such as temperature, pressure, the phase of the material, humidity, etc. Thermal conductivity (k) is the rate at which heat passes through a given material, and it is expressed in W/mK units, where W is thermal energy in Watts, m is the thickness of the material and K is the temperature in Kelvin. 

The steady-state method measures the heat flow through a material of known thickness over a set temperature gradient. This method provides accurate results for solids and liquids. Transient methods offer rapid measurements by observing the material’s temperature response to a quick heat pulse. Laser flash analysis is an example of a transient method. Transient methods are considered ideal for thin films and ceramics.

Modified Transient Plane Source Technique

The Modified Transient Plane Source (MTPS) technique is a quick and versatile method for measuring thermal conductivity. It can measure the thermal conductivity of solids, liquids, and powders in as little as 3 seconds. A similar technique, the Transient Plane Source (TPS), allows the user to configure the power level and test times and can determine thermal conductivity values ranging from 0.03 to 2000 W/mK. The Transient Line Source (TLS) technique is ideal for powders, gravel, soil, and highly viscous or sticky materials like polymer melts. The TLS technique uses a needle probe-style sensor that is fully submerged in a sample and applies heat radially into the sample. The temperature is measured at the center, and the end of the needle, and this rate of change is then correlated to the thermal conductivity of the sample expressed in W/mK.