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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HFM-25 heat flow meter

Features

HFM-25 features
  • Insulation samples as small as 50 x 50 x 2 mm and thickness up to 25.4 mm
  • Large samples can also be loaded for multiple location testing
  • Follows international standards: *ASTM C518, ISO 8301, JIS A1412, and EN 12667

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.

HFM-100 equation

Specification

Methods

HFM-100

HFM-100 HT

HFM-50

HFM-25

Materials

Insulation, solids, and

textiles

Insulation, solids, and

textiles

Insulation, solids, and

textiles

Insulation, solids, and

textiles

Type of Sensors

Flux sensors (x2)

Flux Sensors (x2)

Flux sensors (x2)

Flux sensors (x2)

Thermal conductivity (W/m•K)

0.002 to 0.5

0.002 to 0.5

0.002 to 0.5

0.01 to 0.3

Specific heat

Optional

Optional

Optional

N/A

High thermal conductivity kit (W/m•K)

Optional (up to 2.5)

Optional (up to 2.5)

Optional (up to 2.5)

N/A

Sample size (mm)

300 x 300 x up to 100

300 x 300 x up to 100

200 x 200 x up to 50

Up to 300 x 300 x 25

Test time (minutes)

30 to 40

30 to 40

30 to 40

20

Accuracy (Thermal conductivity) *

1 to 2%

1 to 2%

1 to 2%

3%

Repeatability (Thermal conductivity)

0.5 to 1%

0.5 to 1%

0.5 to 1%

1%

Plate temperature range (°C)

20 to 75**

-30 to 110

-20 to 70**

10 to 75

Factory calibrated

Yes

Yes

Yes

Yes

Standard

ASTM C518, ASTM C1784,

ISO 8301, JIS A1412, EN

12667, and EN 12664

ASTM C518, ASTM C1784,

ISO 8301, JIS A1412, EN

12667, and EN 12664

ASTM C518, ASTM C1784,

ISO 8301, JIS A1412, EN

12667, and EN 12664

ASTM C518, ASTM C1784,

ISO 8301, JIS A1412, and EN

12667

*Performance verified with NIST 1450d / 1450e
**Chilled circulator required

Applications

NIST 1450d high-density fibrous glass board

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

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

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.

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