GHFM-01 Bewachter Wärmemengenzähler

GHFM-01 Guarded Heat Flow Meter is designed to test the thermal resistance and thermal conductivity of both homogeneous and heterogeneous materials.

Ideal für Metals, Polymers, Composites, and Pastes
Bewachter Wärmemengenzähler

The Guarded Heat Flow Meter (GHFM-01) follows ASTM E1530-19 for testing thermal resistance and thermal conductivity of solids, such as metals, polymers, composites and paste from -20 °C to 310 °C. The Thermtest proprietary testing stack, replaces the traditional pneumatic movement with advanced motor control, which allows automated control of testing sample thickness, force or pressure applied.

Eigenschaften

GHFM-01 features

The advanced GHFM-01 is a primary measurement of thermal resistance­—thermal conductivity for solids, such as metals, polymers, composites and paste. Specifically, the calculation of thermal conductivity from measurement of thermal resistance is the most accurate method of testing the true thermal conductivity of heterogeneous materials. The steady-state measurement of thermal resistance represents the full sample thickness and mature heat transfer properties.

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 the sample is achieved, the Fourier law equation can be applied. The ratio RS (m²•K/W), equal to the thickness of the sample, d (m) to its thermal conductivity, λ (W/m•K), can be obtained from the temperatures measured:

GHFM-The-Fourier-Law
The above equation is linear in form, and is the working equation of the instrument. Constants F (m2•K/W) and Rint (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.

Specification

Following international standards, the GHFM-01 is designed for testing both homogeneous and heterogeneous materials.

Materialien

Metals, Polymers, Composites, and Pastes

Type of Sensors

Thermocouples (x6)

Applications

General Testing

Direction

Through-Thickness

Wärmeleitfähigkeit

0.1 to 40 W/m•K

Measurement Time

40 to 60 min.

Accuracy

± 3%

Reproduzierbarkeit

± 1 to 2%

Plate Temperature Range*

-20 to 310 °C

Druck

Automated up to 7 KPa (55 psi)

Sample Diameter

50 to 50.8 mm

Sample Thickness

Up to 25 mm | Thin-films down to 0.1 mm with optional Software

Standard

ASTM E1530-19

*Chilled circulator included with each system

Highlights

Heat Flux Module

Easy to Change Heat Flux Module

No tools are required to change the lower flux module, which forms a calibrated heat flux transducer. Housing multiple thermocouples to monitor temperature for confirmation of steady state condition of the temperature gradient across the sample is achieved.
temperature control ghfm

Temperature Control

Optimally selected heaters cooled by heat exchangers matched with thermocouples, which have a resolution of 0.01 °C are positioned in the upper and lower stack are used to accurately control plate temperatures. Lateral heat loss across the sample thickness is minimized with the use of a guard oven. Upper and lower plate along with guard oven temperatures are fully controlled by the convenient GHFM-01 Software.
thickness measurement ghfm

Thickness Measurement

Accurate sample thickness is required for determining thermal conductivity of a material from the measurement of thermal resistance. The GHFM-01 features a proprietary gimble design, which has the advantage of either an automatic determination of sample thickness, for rigid materials, or a user defined sample thickness, force or pressure applied for compressible materials. Sample thickness is measured using digital optical encoder technology, ensuring the most accurate (± 0.025 mm) measurement of sample thickness.
Operation GHFM

Operation

The GHFM-01 offers a feature packed Windows based software included with each system. The simple to use software offers unlimited automation steps of temperature along with thickness force or pressure settings. Basic testing and calibration steps are fully automated, as well as additional functions like saving, exporting, and printing of measurement results.
Clamping Control GHFM

Clamping Control

For rigid materials, the GHFM-01 plates automatically clamp together for optimum sample contact. When testing compressible materials, the desired height, force or pressure (up to 80 kg, 379 kPa – 55 psi) applied may be set in the software and the plate will automatically stop once desired sample height or pressure is achieved.

Calibration GHFM

Calibration

All conditions of calibration, such as management of reference materials, temperature steps and pressure are fully automated with the GHFM-01 software. Verification of calibration is performed through built in validation routines.

Measurement Process

GHFM Step1

The Sample

GHFM-01 samples should be 50 to 50.8 mm in diameter. The top and bottom surfaces should be flat and parallel. A thin layer of contact paste is added to the top and bottom of the sample surface.
Approximate Time: 1 min.

Place Sample on GHFM-01 Testing Stack

Sample then can be loaded into the testing stack. For rigid materials, upper stack will close to a default pressure. For soft materials, the user can define a specific pressure or required thickness. Pressure and thickness testing parameters can be controlled within the testing schedule.
Approximate Time: 1 min.

Measurement

Using the GHFM-01 Software, the user is able to schedule unlimited temperature steps up to 300 °C. Internal red backlight signals testing in progress.

Approximate Time: 40 to 60 mins.

GHFM-01 Step 4

Export Result Calculations

Temperatures from upper and lower plates are monitored by the GHFM-01 software for temperature stability. Measured thermal resistance and calculated thermal conductivity results are tabulated and available for export to excel. Internal blue backlight signal testing is complete and stack safe to touch.

Approximate Time: 1 min.

Accuracy

Pyrex-7740 Graph

Thermal Conductivity of Pyrex(R) 7740

Demonstrating the performance of the GHFM-01, measurements on Pyrex 7740 were made up to 300 °C and compared to literature values.

Accuracy of all results < 2%.

Thermal Conductivity (W/m•K)

Temperature ( °C)

25

40

60

80

100

120

140

160

180

200

220

240

260

280

300

Direct Measured Values

1.134

1.172

1.192

1.223

1.246

1.261

1.280

1.307

1.325

1.343

1.361

1.386

1.401

1.426

1.451

Literature Values

1.143

1.164

1.214

1.236

1.236

1.257

1.276

1.295

1.313

1.330

1.348

1.366

1.385

1.404

1.426

Error (%)

0.80

0.71

0.11

0.71

0.75

0.33

0.27

0.96

0.92

0.99

0.98

1.44

1.19

1.54

1.78

Guarded Heat Flow Meter (GHFM) Models Comparison


ghfm-01

Modelle

GHFM-01

GHFM-02

Materialien

Metals, Polymers, Composites, and Pastes

Metals, Polymers and Composites

Measurement Capabilities

Through-Thickness

Through-Thickness

Applications

General Testing

General Testing

Wärmeleitfähigkeit

0.1 to 40 W/m•K

0.1 to 15 W/m•K

Sample Diameter

50 to 50.8 mm

50.8 mm / 2 in.

Sample Thickness

Up to 25 mm | Thin-films down to 0.01 mm with optional Software

25.4 mm / 1 in.

Maximum Thickness

25.4 mm / 1 in.

25.4 mm / 1 in.

Temperaturbereich

-20 to 310 °C*

20 to 30 °C

Druck

Automated up to 379 kPa (55 psi)

Manuell

Measurement Time

30 to 45 minutes

30 to 45 minutes

Accuracy

± 3 %

5 %

Reproduzierbarkeit

± 1 to 2 %

2 %

Standards

ASTM E1530-19

ASTM E1530-19

*Chilled circulator included with each system

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