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In order to accurately predict the performance of a cooling module in an underhood environment, it is essential that the heat fluxes to the air from the various heat exchangers, such as radiator, condenser and charge air cooler, are modeled properly. Simulation models should therefore involve the prediction of the flow and temperature fields in both air and liquid side of heat exchangers. At Behr GmbH & Co., different simulation tools are successfully integrated in the development process to meet this goal. For underhood flow simulations, heat exchanger analysis programs are coupled directly with the flow solver. In order to verify the simulation a validation program has been set up based on the fact, that the air mass flow rate through the cooling module has a major influence on the performance of the radiator. Therefore, calculated air mass flow rates through the radiator were compared with the experimentally measured flow rates.

This paper describes the use of computational fluid dynamics (CFD) as a tool to investigate fluid flow and heat transfer characteristics in louvered fin heat exchangers that are widely used in automotive industry. CFD supplies you with information from inside the heat exchanger like spatial distributions of temperature and velocity fields between the fins. The right interpretation of this information can reduce the number of prototypes and thus save time and money in the development process. Variations of grid density, differencing schemes and boundary conditions have been performed in 2D to ensure the reliability of the numerical results. With the recommendations of the 2-D study 3-D calculations have been made. The numerical results show good agreement with experimental data. The experimental values for overall pressure drop and heat transfer have been obtained using a test facility for heat exchangers at Behr.

For HVAC systems this paper describes “excellent” acoustics and criteria and tools for acoustic evaluation. Focusing on the HVAC subsystem “air flow”, it further outlines four columns on which acoustic is based. Finally this paper discusses aspects how the vehicle design process which can facilitate acoustic optimization of HVAC systems.

In this paper a study of different front end and cooling module designs on the engine cooling performance by means of simulation tools is presented. Various configurations of grille and front end intake geometries of a BMW 5 series passenger car are investigated at different operating points concerning mass flow and mass flow distribution on engine cooling components. Different cooling module configurations were studied concerning the position of an additional motor oil cooler. The simulations were done with 1D Behr Integrated System Simulations Software (BISS) as well as the commercial 3D Navier-Stokes solvers UH3D and Star-CD. BISS and CFD software are coupled by passing the results as boundary conditions enabling to use the full potential of both 1D and 3D modeling. Differences between UH3D and Star-CD modeling assumptions are discussed and advantages and disadvantages concerning accuracy and turnaround time are quantified.

Next to air temperature, humidity, and air quality, it is sound emission that exerts a significant impact on the driver's and passenger's comfort. Major progress in vehicle acoustics has motivated vehicle manufacturers and systems suppliers to evaluate HVAC systems no longer by their air conditioning performance alone. Sound emissions and sound quality have become additional important criteria for the development of new HVAC systems. In the initial conception phase, where systems and packaging considerations are made, acoustic optimization must begin with preliminary system studies and feasibility studies. In this phase acoustics should be based on fairly general systems specifications which describe the desired degree of acoustic comfort. In the subsequent design phase follows the specification of the acoustic goals and the optimization of the HVAC unit. Detailed analysis and optimization of air flow and blower are the common targets for improvement at this time.