HFM-25 Heat Flow Meter

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.

Best for small samples of insulation and construction materials

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Heat Flow Meter (HFM) 25 was designed for the measurement of thermal resistance and thermal conductivity of small samples of insulation and
construction materials. Offering the testing power of a full-size heat flow meter optimized for small insulation samples and budget

Features

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 use of standard weights. Thickness is conveniently reported with included digital gauge. Testing on compressible samples is possible with included shims.

Designed for room temperature operation, 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.

Specification

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
Maximum Sample Thickness	25.4 mm
Maximum Sample (LxW)	Unlimited
Standard	ASTM C518*, ISO 8301, JIS A1412, and EN 12667

* Applies for materials below 0.1 W/mK

Applications

Location Testing for Homogeneity

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 then 1%, confirming the homogeneity.

Aerogel Blanket

Aerogel blanket sample (50 x 50 x 9.58 mm) was selected to test by the HFM-25. Thermal conductivity of 0.014 W/m•K was measured at 23°C, which is within 3% of the manufacturer’s specification (measured by GHP – ASTM C177).

NIST SRM 1450d

A sample of NIST SRM 1450d was measured for thermal conductivity for accuracy. The certified thermal conductivity for the NIST piece at 25°C is 0.0329 W/m•K. The measured thermal conductivity was 0.0330 W/m•K, which is within 1% of the certified value.

Heat Flow Meter (HFM) Models Comparison


Models	HFM-100/HFM-100 HT	HFM-50	HFM-25
Materials	Insulation, Solids, Construction Materials	Insulation, Solids, Construction Materials	Insulation, Textiles
Type of Sensors	Flux Sensors (x2)	Flux Sensors (x2)	Flux Sensors (x2)
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	Optional (Up to 2.5 W/m•K)	Optional (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 75 °C / -30 to 110 °C**	-20 to 75 °C*	10 to 40°C
Maximum Sample Size	300 x 300 x up to 100 mm	200 x 200 x up to 50 mm	75 x 75 x up to 25mm
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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HFM-25 Heat Flow Meter

Features

Specification