To meet customer requirements, air conditioning units must be designed with detailed attention to airflow management. The best compromise must be found between pressure, flow-rate, thermal comfort, noise level, energy consumption, packaging and cost.To get quick results from CFD runs, a clever strategy is essential. Since successive design ‘tuning’ operations are necessary, a time-efficient meshing technique is required. To simulate HVAC units one has to model an elaborate assembly of heat exchangers, internal flaps and outlet ducts. Moreover simulation of several operating points is required to evaluate global performance. For each configuration, this implies the need to handle a combination of blending and distribution flap positions, activated outlets and air flow rates. To cope with this kind of complexity we found that STAR-CD’s custom mesh capabilities to be very useful. Our approach has been to represent as many configurations as possible on the same mesh, and then to switch boundary conditions from one case to another.The first step is to import the CAD model into pro-STAR using its native CAD reader (CATIA V4); then the surface mesh is generated. At the same time, 2D sections are created in the CAD software, in order to generate custom mesh parts that rely on the domain topology including all flap positions. The final pre-processing step is to mesh the whole volume, using the custom mesh method. After running the STAR-CD solver, we found that the post-processing operations could be automated in a highly efficient way, provided that best practice was followed during the preparation of the cases.
CFD is widely used at VALEO Climate Control, in order to support product design definition. Through efficient STAR-CD implementation in the design process, we have been able to reduce the number of prototypes and cut costs.Finally, we have learnt that the complementary use of experimental and simulation resources, is clearly the way to designing robust products.
