Thermo-Technical Laboratory

The thermal technical laboratory at Fraunhofer IFAM Dresden provides excellent equipment for the metrological determination of thermophysical material and transport parameters as well as characteristic thermal and flow parameters of various materials and material composites. In combination with the many years of experience gained by our employees in the Energy and Thermal Management business unit, we are able to solve any of your measurement tasks.  

Examples of the parameters analyzed include:

• density and specific heat capacity,
• thermal conductivity, heat transfer coefficients in gas and liquid flows and evaporating or condensing media, and
• permeabilities and pressure loss coefficients at flow.

In addition to materials with isotropic properties, composite materials (layer, fibre or particle composites) with direction-dependent characteristics, porous structures and numerous other samples - especially phase change materials - can also be investigated.

The basic equipment of the laboratory includes:

• stationary and non-stationary measuring methods for determining the thermal conductivity at variable temperatures,
• installations for the production of tempered gas or liquid flows,
• test systems for the cyclic loading and unloading of heat storage elements,
• evaporator test stands
• efficient measuring and data acquisition systems for temperatures, pressures, speeds and other measured variables.

In addition to the use of existing laboratory equipment, we are happy to develop test apparatus for the implementation of special customer-specific measuring tasks.

Physical and chemical properties of a material, a substance, a mixture of substances and / or reaction mixtures are measured as a function of temperature, time or pressure using the methods of thermal analysis. A controlled temperature-time program and a defined atmosphere are applied during the measurement.

Analytical methods that are available at Fraunhofer IFAM Dresden for research and development purposes:

Push rods dilatometry (DIL) (accredited procedure)

• Thermal expansion behavior (temperature-density curve, shrinkage, swelling)
• Thermal expansion coefficient

Optical dilatometry (DIL)

• Thermal expansion behavior (temperature-density curve, shrinkage, swelling)
• Thermal expansion coefficient
• Heating microscopy, contact angle measurement

Thermal conductivity (TC)

• Thermal diffusivity and thermal conductivity of powder, porous bodies and material combinations
• Methods: Hot plate, Hot Disk, Flash
• Specific heat capacity

3-layer-calorimeter

• Specific heat capacity
• Phase change enthalpy

Dynamic Difference Calorimetry (DSC)

• Specific heat capacity
• Melting, solidification and crystallization processes, recrystallization
• Dissolution and elimination processes
• Phase formation
• Determination of reaction enthalpies
• Self-ignition behavior

Thermogravimetry (TG)

• (De) hydrations, (de) hydrations,
• Drying, evaporation, evaporation, sublimation
• Debinding, dewaxing, dewatering, degassing
• Decomposition (pyrolysis, burns)
• Oxidation, reduction, corrosion and stability under defined conditions
• Cyclic oxidation test

Simultaneous thermal analysis (STA) as a combination of thermogravimetry (TG) and dynamic - difference - calorimetry (DSC)

• Realizable heating rate up to 500 K/min in the temperature range between 25 °C and 1200 °C

Mass spectrometry (MS)

• Determination of fragments in the mass number range from 1 to 250
• Can be coupled with DIL, DSC, TG, STA

Further information on the available methods of thermal analysis at Fraunhofer IFAM Dresden.

For many applications in the field of heat transfer, heat storage and heat management, knowledge of the thermal and fluidic properties of (composite) materials is of great importance. These include essentially:

• the determination of heat transfer coefficients with forced convection during the flow through cellular metal structures (metal foam, metal fiber, metal wire structures) or during the flow over/around components with functionalized surfaces (e.g. project HeatCNT),
• the measurement of heat transfer coefficients with free convection on functionalized surfaces (e.g. structured evaporator surfaces),
• the measurement of permeabilities or pressure loss coefficients in or on structures through or over flowed structures.

For this purpose, the thermal engineering laboratory is optimally equipped to generate defined flow conditions in channels or on free surfaces in the form of

• Air flows with specified flow velocity (fan or mass flow controller) and temperature (electric air heater up to max. 20 kW heat output),
• Water flows up to 5 litres/min (Coriolis flow controller) with temperatures up to 95 °C (electric instantaneous water heaters up to max. 20 kW heating capacity), and
• Thermal oil flows (adjustable pump) up to max. 350 °C in a closed circuit.

Furthermore, modern flow, velocity, pressure and temperature measurement technology is available to characterize the flow conditions. The required coefficients are either determined from direct measured variables or with the help of suitable energy balances.

Thermoelectric modules allow the direct conversion of heat into electrical energy without moving parts and are therefore an ideal technology for e.g. using waste heat. The thermoelectric modules developed at the Fraunhofer IFAM Dresden or by external partners can be characterized in the thermo-technical laboratory in two ways:

• The dynamic behaviour of the modules provides information about their mechanical properties under alternating thermal stress, which, for example, causes the modules to warm up and cool down when a thermoelectric generator is started up and shut down. Temperature gradients are cyclically generated in the modules by electrical heating or air cooling in a specially developed test facility [(1) in the picture], which correspond to the practical operating conditions. Subsequently, the optical or mechanical testing of the modules takes place.

• The stationary behaviour of the modules provides information about the electrical power that can be generated when coupled to the flow of a heating medium (hot air up to 600 °C and higher) and a cooling medium (cold air or cooling water up to 90 °C). The thermal efficiency of the thermoelectric modules can be calculated from these measurements in combination with a thermal conductivity measurement.