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Heat management must allow the adjustment of optimal operating temperatures of all components of a vehicle. A comprehensive simulation model (KULI) will contain all components relevant for heat management. This includes heat sources, heat exchangers, fans, etc. Main aspects of the simulation are flow and heat transfer analysis. Not only the engine cooling system can be covered with this simulation tool, also the air-conditioning circuit including phase changing models is a part of it (KULI AC). To fulfill the needs of integrating various software tools to an overall simulation cluster an interface to a fluid flow 1-dimensional software (FLOWMASTER) was developed. The use of 1- dimensional methods and mesh flow theory for modeling the underhood air flow of vehicles is very efficient method. For complex flow patterns however it is desirable to use CFD analysis.

An efficient air-conditioning system is an important factor for the commercial success of an automotive product, because of the thermal comfort for the passengers being an important incentive for the purchaser. A simulation tool is presented that makes it possible to design and optimize A/C refrigerant circuits together with the engine cooling system in a very early stage of the design process. This tool is based on networks including the enhanced heat exchange theory which also takes into consideration refrigerant phase changes. A graphical user interface and predefined simulation models which are based on the respective geometry of the system components make it easy to create a virtual vehicle for mathematical analysis of the various heat and mass flows. High flexibility and short calculation time together with high accuracy enable the engineer to make efficient investigations.

This paper shows one example of cooling system, optimized by utilizing computer simulation in the early development stage. First, a numerical simulation is conducted to obtain the air flow rate through engine compartment room by the software “STREAM”. Second, ΔTw are calculated by the software “KULI”, developed by Steyr-Daimler-Puch AG, to evaluate the original cooling system. Third, the optimization of this system is conducted by the design of experiment for cost saving and weight reduction. The test value was well matched with the calculated one and CAE was confirmed to be very helpful for saving the proto-build cost and time period.