Measuring the Thermal Conductivity of Multi-Purpose Grease

The Measurement Platform-2 (MP-2) is an advanced meter with unique selection of transient thermal conductivity sensors for a variety of applications, with a focus on primary measurements. The transient thermal conductivity sensors share similar principles of operation. The sensor wire is heated using a constant current source (q) and the temperature rise is recorded by monitoring the change in electrical resistance of the wire (THW and EFF) or by resistance temperature detector device (TLS). For samples of high thermal conductivity, the lower the slope; for samples of low thermal conductivity, the higher the slope.

Picture 1. Thermtest MP-2 Thermal Conductivity Meter

Thermal conductivity MP-2 users benefit from the convenience and accuracy gained when using primary testing methods. The MP-2 controller auto-detects the connected sensor and loads corresponding testing parameters. Measurements are easily performed with the smart on-board software and transferred to computer with an included Windows utility program.

THW-L3 Sensor

Picture 2. Thermtest THW-L3 sensor for use with the MP-2 portable meter.

The THW-L3 sensor is one of the many sensors offered with the Thermtest Portable Measurement Platform (MP-2). This sensor offers simple yet accurate measurements of liquids, pastes, and powders from 0.01 to 1 W/m/K via the transient hot wire method. The THW-L3 adheres with an internationally recognized standard of testing by complying with ASTM D7896-19. The THW-L3 has a 5% accuracy and a 2% reproducibility of measurement, making it a highly accurate and precise instrument for measuring the thermal conductivity of liquids, pastes, and powders.

The THW-L3 has a detect current setting that determines the appropriate amount of current to apply based on a test measurement. By reading the result of the test measurement, a current will be set that results in an optimal temperature rise of the sample during testing. Due to the compact size of the THW-L3 sensor, it can be inserted directly into the grease container, making sample setup very straightforward (Figure 1). It is worth noting that WD-40 makes for an excellent solvent for removing grease from the sensor after testing.

Thermal Conductivity of Grease

Multi-purpose greases are primarily used for automotive and industrial applications to lubricate machine parts. The application of grease reduces the amount of friction on the parts during use, improving their performance and longevity. When they are in use, moving parts can overheat resulting in either reduced longevity or damage to the part. It is for this reason that a type of grease with the ability to pull (or conduct) heat away from moving parts would be useful. This ability to conduct heat is referred to as thermal conductivity, and this a material property that can be measured in grease quickly and accurately with the Thermtest THW-L3 sensor.

Figure 1: a) Setting up a sample of multi-purpose grease with the THW-L3, b) MP-2 with the THW-L3 sensor and sample cell.