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A significant driver for the development of future commercial vehicles is likely to be the introduction of fuel consumption related legislation in various regions around the world. The application of a waste heat recovery system to the powertrain of such vehicles is seen as a possible step, amongst many, to help them achieve the required fuel economy. In particular, the Rankine Cycle (a closed steam cycle) is often proposed as a potential means for deriving work from the engine exhaust heat. Rankine Cycle systems are already in use in off-highway applications, such as stationary engines or marine power-packs. However, the technical and commercial viability of these systems for on-highway, principally long haul truck application is as yet unproven. Aspects such as the in-use economy benefits, the system performance density, the component robustness and all interactions with the other vehicle systems have to be evaluated.

Aluminum has a number of features which make it superior to the other non-ferrous metals (copper and brass) normally used for radiators in the past. Apart from the low specific weight, there are additional advantages, such as outstanding heat conductivity, strength, corrosion resistance and convenient forming and processing qualities. Brazed aluminum radiators with flat tubes and louvered serpentine fins are used for high horsepower engines and/or in confined spaces, while mechanically assembled round tube or oval tube radiators are preferred for smaller engines and/or where there is sufficient space. The excellent field results with car radiators have led to the use of aluminum radiators in trucks as well. More than 10 million fluxless brazed flat tube radiators with serpentine fins have been manufactured by Behr since 1975. Serial production for trucks was started in 1988.

Modern trucks have to meet tough regulations for environment protection, which concern considerable reductions of fuel consumption, exhaust gas emissions and noise emission. As the fuel consumption rate of motor vehicle is directly influenced by its weight, reduction of the latter has high priority in the construction of vehicles. The use of compact, lightweight, high performance heat exchangers in engine cooling systems supports weight saving. High efficient charge air cooling improves not only the engine power, but also the fuel consumption, the exhaust gas emission and the life time of the engine. In addition a new developed jet ring fan ensures a stable air flow through the complete cooling system; combined with the Visco® clutch very low noise levels can be achieved. All these products are already manufactured in environment-friendly processes with easy recyclable materials.

When considering charge-air cooling in vehicle engines, it is necessary to distinguish between commercial and passenger applications on the one hand, and Diesel and gasoline engines on the other. The requirements for the various types of application will be outlined, and the characteristics of the various charge-air cooling systems discussed. In general, heat transfer rate and pressure drop are considered in evaluating the suitability of a charge-air cooler for a particular purpose. The effectiveness of such a procedure, however, tends to be limited. In order to create new criteria for evaluation, new terms such as the efficiency of density recovery and “half-value performance” have been developed. Optimisation of the core geometry according to the requirements and desired objective functions is necessary and shows that one single system cannot meet the wide range of requirements. Some practical applications and future trends are outlined.

The Aluminum radiator has a number of features that make it very attractive for vehicle applications in general. Superior durability and reliability in conjunction with its excellent specific values for costs, performance and weight warrant a favorable solution for Heavy Duty Trucks. Behr has been supplying Aluminum radiators for trucks in Europe for over 10 years and in North America for 4 years. This paper examines the results based on this long-term experience. It reviews the field experience compared to Copper/Brass radiators, examines design and mounting features as well as the manufacturing processes. Durability, external and internal corrosion resistance are emphasized as essential characteristics. A special focus is the thermodynamics of Aluminum radiators. The paper reviews methods to simulate the thermodynamic behavior of radiators and the progress in the specific performance, based on the development of improved radiator core matrices.