Hot Disk Transient Plane Source (TPS)

TechniqueFor Measurement of Thermal Conductivity, Thermal Diffusivity and

Specific Heat

Thermtest Inc.

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TPS 3500 Thermal Conductivity Instrument

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Hot Disk Transient Plane Source Technique

• Absolute method for the measurement of thermal conductivity and thermal diffusivity, with calculation of specific heat and thermal effusivity

• No calibration required in order to make measurements

• No contact agent required between sensor and sample

• Thermal conductivity from 0.001 W/m•K up to 1800 W/m•K

• Temperatures from - 250 °C up to 1000 °C

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TPS Models

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TPS Model Thermal Conductivity Range (W/m•K)

Temperature Range (°C)

Hot Disk TPS 3500 0.001 to 1800 -160 to 1000

Hot Disk TPS 2500 S 0.001 to 1000 -160 to 1000

Hot Disk TPS 2200 0.03 to 500 -160 to 750

Hot Disk TPS 1500 0.001 to 20 -160 to 1000

Hot Disk TPS 500 S 0.03 to 250 -160 to 300

Hot Disk TPS 500 0.03 to 100 -160 to 200

• Different models are available, depending on budget and applications

TPS Testing Modules• Different testing modules are available:1. Standard: for measurement of bulk thermal conductivity and thermal

diffusivity of isotropic solids, liquids, pastes and powders2. Anisotropic: for measurement of directionally-dependent (in-plane and

through-plane) thermal conductivity and thermal diffusivity3. Slab: for thin, highly thermally conducting materials4. Thin film: for measurement of coatings and stand-alone films5. 1-Dimensional: for 1D measurement of elongated materials like rods6. Specific Heat: direct measurement of specific heat

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TPS Sensors• The TPS sensor is comprised of a planar 10 µm double nickel spiral covered on both sides by a

protective film (either Kapton, Mica or Teflon depending on the desired temperature and application)

• Kapton: Up to 300 °C• Mica: Up to 1000 °C• Teflon: Acidic or corrosive environments

• Different radii sensors are available

• From left to right: Kapton, Mica, Teflon

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Probing Depth

• The TPS theory assumes that the sensor is in an infinite medium of sample, and thus the probing depth (penetration of heat)must not exceed the boundaries of the samples

• Thermal diffusivity of a material will determine probing depth during measurements

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Experimental Parameters• An appropriate power output is chosen so as to raise the temperature of the

sample between 1 and 4 °C

• Highly thermally conductive materials will require higher power output than thermally insulating materials

• A measurement time is chosen so as to allow the introduced heat to penetrate some distance into the sample, but not reach the outer bounds of the sample pieces

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Two-Sided Experimental Sample Setup

• The sensor is clamped in to the sample holder• The bottom sample piece is placed on the adjustable plate, which is raised so the bottom sample makes contact with the sensor• The top sample piece is placed on top of the sensor and a light pressure is applied to ensure good contact between sensor and sample

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Single-Sided Experimental Sample Setup

• A single-sided sensor is also available for use if two pieces of the same material cannot be prepared• A highly insulative, known backing material is used underneath the sensor to prevent heat loss to the surroundings• The sensor is spring-loaded to help ensure good contact between sensor and sample and a weight is also placed on top of the sample to improve contact• The sensor can also be placed upside down on a sample

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Hot Disk Software

• Experiment parameters are entered on the input screen: - Sample Identity - Available Probing Depth - Sensor Type and Radius - Measurement Temperature - Measurement Time and - Heating Power

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Hot Disk TPS Software

• Baseline temperature drift is monitored before the experiment and a correction is applied if needed

• Temperature increase vs. time graph is plotted, which thermal conductivity is derived from

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Hot Disk TPS Software

• 200 data points are collected for each transient measurement

• Some of these points near the start will be eliminated to remove the effect of contact resistance between the sensor and sample

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Hot Disk TPS Software

• Slope is plotted from the T increase vs. time graph, which gives thermal conductivity

• A residual plot is also included, which compares data to the curve fit, providing extra confidence

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Hot Disk Software• Results are calculated and shown for each experimental run• Guiding warnings are provided for Total to Characteristic Time and Total Temperature Increase to ensure

optimized parameters are used. A yellow or red warning means that the parameter was slightly off (yellow) or significantly off (red). Simple power and time adjustments can then be made.

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Conclusions

The hot disk transient plane source technique:- Direct thermal property measurement, no complex calibration required- Is multi-property: thermal conductivity, thermal diffusivity and specific heat- Homogeneous and heterogeneous- Isotropic and anisotropic- Solids, liquids, pastes and powders- No contact agent required- Two-sided and single-sided sensors

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