Optimization of HVAC Temperature Regulation Curves with modeFrontier and Fluent

Simultaneously obtaining a linear temperature control curve along with the correct temperature stratification at module outlets is one of the most difficult tasks in developing an automotive HVAC module. Traditionally, Computational Fluid Dynamics (CFD) development of temperature control linearity has been accomplished by iteratively adjusting the location, size and orientation of baffles which redirect warm and cold airstreams. This approach demands considerable interaction from the engineer in building the computational mesh, defining boundary and operating conditions and post processing the simulation results. The present study was conducted to investigate the optimization of HVAC temperature regulation curves using the multi-objective optimization code modeFrontier (1, 3) in conjunction with CFD code, Fluent (2). An auxiliary HVAC module was selected for the present study. The diffuser of the model was omitted from the computational domain in order to reduce the model size resulting in faster turn around time. The penetration depths into the flow domain of two deflector baffles were the key parameters considered for optimization. The objective of the optimization is to obtain linear temperature control at HVAC outlets with a minimal increase in pressure drop. Three different temperature door positions were investigated for each combination of deflector sizes. Based on the temperature readings, the objective function was calculated and minimized as follows. The initial population was created using the DOE method. Several techniques including construction of the response surface were utilized to identify the optimum solution for the present study.