TGM Special: Concept Carbon Heat Exchanger

The status quo

Typically, heat transfer systems for air cooling in the automotive sector are designed as metallic finned heat exchangers with focus on corrosion and media resistance. This design generates a large transfer surface within limited package, but the materials currently used result in an increased dead weight, which is also leads to heavier surrounding structures. In most vehicles, integration of the function into existing structural components is not possible due to the material and the design.
As a result, the required installation space and the usable air flow are usually predefined. As a result of contamination and mechanical effects (such as bent fins), the amount of air flowing through the system decreases over its lifetime, which reduces the efficiency of current heat exchanger systems.
These influences limit the engine performance or efficiency of the combustion process and show clear disadvantages of existing systems when adapting to further applications for cooling or heating in the field of hybrid or electric drives. In the context of functional lightweight design, structural elements should also be used as heat exchangers for cooling or heating.

The principle

In contrast to metallic materials such as aluminium, where thermal conductivity is isotropic, the thermal conductivity of carbon fibres is generally strongly anisotropic and highest in fibre direction. High-modulus carbon fibres have six times the thermal conductivity of aluminium.
Current finned heat exchangers require the largest possible transfer surface to achieve the required performance and therefore typically consist of several cooling loops. The use of thermally conductive materials, on the other hand, enables improved heat transfer, which reduces the surface area, lowers the system weight, and increases the degree of design freedom. In perspective, this also enables the activation of the entire air duct for heat exchange.

Possible applications in the automobile

Heat exchangers made of carbon-based materials are already in use in stationary applications such as heat and power plants and enable new types of lightweight solutions in the automotive and power electronics sector. Depending on the design, higher cooling capacities (approx. 40%) or lower vehicle weights can be achieved. By integrating the functions into existing structural components, optimal geometries regarding lower air resistance and improved crash energy absorption can be implemented at the same time.
Conceivable applications in the automobile are wide-ranging and include, for example, functional integration in the structural components of the air intakes, radiator grilles, splitters, underbody panelling, side skirts, spoilers and crash elements for unit and transmission cooling.

The project team

Based on the research results of the department of polymer-based lightweight construction at the BTU Cottbus and our many years of experience in technical weight management, we have already applied for a joint patent and developed an initial concept sketch together with our partners Fraunhofer PYCO, the engineering office Christan Marmodée and Realize Engineering.

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