The Guarded Heat Flow Meter (GHFM-02) follows ASTM E1530-19 for testing thermal resistance and thermal conductivity of solids, such as metals, polymers and composites. The easy to operate GHFM-02 follows the trusted steady-state approach, with the addition of a guard to limit the effects of lateral heat loss. This design, allows testing of a wide range of materials with low to medium thermal conductivity.

According to the method, the sample is subjected to a steady-state through-thickness temperature gradient. The thermal conductivity of the sample is obtained by measuring the temperature difference across it, and one additional temperature.

The testing stack is made up of a heater – upper plate, with integrated temperature sensor and heat sink – lower plate with integrated temperature sensor on each side of the sample. Additional temperature sensors are placed near the top and bottom surface of the sample.

Once steady-state temperature across sample is achieved, the Fourier law equation can be applied. It can readily be shown that for any solid sample, the ratio R_S (m² K/W), equal to the thickness of the sample, d (m), to its thermal conductivity, λ (W/mK), can be obtained from the temperatures measured:

The above equation is linear in form, and is the working equation of the instrument. Constants F (m² K/W) and R_int (m² K/W), can be obtained by calibration of the instrument. To this effect, calibration samples of known thermal conductivity and hence, thermal resistance, are employed. Calibrated results for thermal resistance and thermal conductivity are reported.