The HFM-25 is a portable heat flow meter for the measurement of thermal resistance and thermal conductivity of small samples of insulation and construction materials.
The economic HFM-25 was designed to meet the growing need for steady-state testing of small samples of insulation for true thermal resistance and thermal conductivity.
Designed with simplicity in mind, a sample is positioned between the two heating – cooling plates. Plate contact is controlled manually, with variable pressure applied with the use of standard weights. Thickness is conveniently reported with included digital gauge. Testing on compressible samples is possible with included shims.
Ambient room temperature is automatically detected, users can choose from 5, 10, 15, and 20 °C delta ranges. One heat flux sensor is integrated into each plate and is used to monitor heat flux (Q/A), generated due to the difference in temperature (ΔT) between the top and bottom plate at regular intervals until steady-state heat flux is observed. The composite heat flux is then used to measure thermal resistance (R) and calculate thermal conductivity (λ) according to Fourier’s Law.
Thermal Conductivity | 0.01 to 0.3 W/m•K |
Directions | Through-Thickness |
Accuracy | 3% |
Reproducibility | 1% |
Temperature | Delta 5°C, 10°C, 15°C and 20°C at ambient temperature |
Type of Sensors | Flux Sensors (x2) with surface thermocouples |
Minimum Sample Size | 50 x 50 x 2 mm |
Maximum Sample Size | 25.4 mm |
Maximum Sample (LxW) | Unlimited |
Standard | *ASTM C518, C1784, ISO 8301, JIS A1412, and EN 12664 |
* Applies for materials below 0.1 W/mK
The homogeneity of NIST 1450d high-density fibrous glass board was measured with the HFM-25. Designed to test small samples or locations of 25 mm x 25 mm. The open concept sample clamping allows testing of large samples.
The four corners of the board were measured to analyze the homogeneity of sample. The % RSD from location to location was less than 1%, confirming the homogeneity
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Models | |||
Materials | Insulation, Solids, Construction Materials | Insulation, Solids, Construction Materials | Insulation, Textiles |
Type of Sensors | Flux Sensors (x2) | Flux Sensors (x2) | Flux Sensors (x2) |
Applications | General Testing | General Testing | Small Insulation |
Direction | Through-thickness | Through-thickness | Through-thickness |
Thermal Conductivity Range | 0.002 to 0.5 W/m•K | 0.002 to 0.5 W/m•K | 0.01 to 0.3 W/m•K |
Specific Heat | Optional | Optional | N/A |
High Thermal Conductivity Kit | Up to 2.5 W/m•K | Up to 2.5 W/m•K | N/A |
Measurement Time | 30 to 40 minutes | 30 to 40 minutes | 20 minutes |
Reproducibility | ± 0.5 to 1% | ± 0.5 to 1% | 1% |
Accuracy | ± 1 to 2%* | ± 1 to 2%* | 3% |
Plate Temperature Range | -20 to 70 °C† | -20 to 70 °C† | 10 to 40°C |
Smallest Sample Size | 250 x 250 x 5 | 150 x 150 x 5 | 50 x 50 x 2 |
Maximum Sample Size | 300 x 300 x 100 | 200 x 200 x 50 | 300 x 300 x 25 |
Standards | ASTM C518, C1784, ISO 8301, JIS A1412, EN 12667, and EN 12664 |
*Performance verified with NIST 1450d / 1450e | †Chilled circulator required
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