GHFM-01 Guarded Heat Flow Meter

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 300 °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.

GHFM-01 Specification

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

MaterialsMetals, Polymers, Composites, and Pastes
Type of SensorsThermocouples (x6)
ApplicationsGeneral Testing
DirectionThrough-Thickness
Thermal Conductivity Range0.1 to 40 W/m•K
Measurement Time40 to 60 min
Accuracy± 3%
Repeatability± 1 to 2%
Plate Temperature Range*-20 to 310 °C
PressureAutomated up to 7 KPa (55 psi)
Sample Diameter50 to 50.8 mm
Sample ThicknessUp to 25 mm | Thin-films down to 0.1 mm with optional Software
StandardASTM E1530-19

*Chilled circulator included with each system.

GHFM-01 Highlights

Easy to Change 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

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

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

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

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, 7 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

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.

Accuracy

Pyrex(R) 7740 Thermal Conductivity

Pyrex(R) 7740 Thermal Conductivity

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 1.190 1.214 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

Sample Measurements

the sample

1

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 minute

Place Sample on GHFM-01 Testing Stack

2

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 minute

Measurement

3

Measurement

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

Approximate Time: 25 to 30 minutes

Export Result Calculations

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 minute

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