The Transient Hot Wire Liquid Thermal Conductivity Meter (THW-L1) is a precision analytical instrument for directly measuring the thermal conductivity of liquids and low viscosity pastes, from 10 to 200°C.
Figure 1. Thermtest THW-L1 Liquid Thermal Conductivity Meter
The Thermtest Transient Hot Wire (THW-L1) liquid thermal conductivity equipment is an advanced measurement system for direct determination of the thermal conductivity liquids and pastes in accordance with ASTM D7896-19 – Standard Test Method for Thermal Conductivity of Engine Coolants and Related Fluids by Transient Hot Wire Liquid Thermal Conductivity Method.
The THW-L1 Meter was designed with speed and operational simplicity in mind. With a single measurement of 1 second in duration, small volumes of liquids and low viscosity pastes can be accurately and precisely measured for thermal conductivity, thermal diffusivity and specific heat. The THW-L1 Meter uses a non-stationary measurement approach and rapid test times limiting convective effects for samples with a wide range of viscosities (0.1 to 10,000,000 mPas).
A new open-bottom measuring cell (Figure 2) used to measure the thermal conductivity of ambient density powders with varying mean particle size. The new cell allows the powder sample loading without changing the powder properties.
The samples measured were a Silica powder with particle size 7 nm, an Aluminum oxide 99.5 % with particle size 37 nm, and a Boron nitride powder with particle size 55-65 μm. The measuring time for all the powders was 5 s and the results at 18 oC are given in Figure 3.
A)
B) 
Figure 2. a) Measuring Cell for the measurements of powders and b) Loading of the powder to the measuring cell.
Figure 3. Thermal conductivity of the three powders as a function of the particle size.