TGM Special: Carbon Heat Exchanger concept

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The status quo

Typically, heat transfer systems for air cooling in the automotive sector are designed as metallic finned heat exchangers and designed for corrosion and media resistance. This design enables a large transfer surface with limited installation space, but the materials currently used result in an increased dead weight, which is also reflected in the heavier surrounding structures. In most vehicles, the material and design mean that it is not possible to integrate the function into existing structural components.
As a result, the required installation space and the usable air flow are usually predefined. As a result of soiling and mechanical effects (which bend the blades, for example), the volume of air flowing through decreases over the service life, which reduces the efficiency of current transfer systems.
These influences limit the engine performance and efficiency of the combustion process and show clear disadvantages of existing systems when adapting to other applications for cooling or heating in the area of hybrid or electric drives. In the context of lightweight functional design, structural elements should also be used as heat exchangers for cooling or heating.

The active principle

In contrast to metallic materials such as aluminum, where heat conduction is isotropic, the thermal conductivity of carbon fibers is generally highly anisotropic and highest in the direction of the fiber. High-modulus carbon fibers have six times the thermal conductivity of aluminum.
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. This also opens up the prospect of activating the entire air duct for heat exchange.

The application possibilities in the automobile

Heat exchangers made of carbon-based materials are already in use in stationary applications such as combined heat and power plants and enable innovative lightweight solutions in the automotive and power electronics sectors. Depending on the design, higher cooling capacities (approx. 40%) or lower vehicle weights can be achieved. By integrating functions into existing structural components, optimum geometries can also be implemented with regard to lower air resistance and improved crash energy absorption.
Conceivable applications in the automobile are wide-ranging and include, for example, the integration of functions into the structural components of air intakes, radiator grilles, splitters, underbody panels, side skirts, spoilers and crash elements for engine 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, a joint patent has already been applied for and an initial concept sketch has been drawn up together with our partners Fraunhofer PYCO, the engineering office Christan Marmodée and Realize Engineering.

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