Parametric Modelling and Performance Analysis of HVAC Defroster Duct Using Robust Optimization Methodology 2020-01-1250

Nowadays development of automotive HVAC is a challenging task wherein thermal comfort and safety are very critical factors to be met. HVAC system is responsible for the demisting and defrosting of the vehicle’s windshield and for creating/maintaining a pleasing environment inside the cabin by controlling airflow, velocity, temperature and purity of air. Fog or ice which forms on the windshield is the main reason for invisibility and leads to major safety issues to the customers while driving. It has been shown that proper clear visibility for the windshield could be obtained with a better flow pattern and uniform flow distribution in the defrost mode of the HVAC system and defrost duct. Defroster performance has received significant attention from OEMs to meet the specific global performance standards of FMVSS103 and SAE J902. Therefore, defroster performance is seriously taken into consideration during the design of HVAC system and defroster duct.

The HVAC unit provides hot air to the defroster duct which is blowing high velocity air to the windscreen to clear the frosting. Currently as a traditional defrost duct design process, multiple flow simulation needs to be carried out for various design configurations of defrost duct through CFD analysis until the performance targets are achieved during the design cycle and it is very time consuming. In this paper, the focus is to develop defrost duct modelling using parameterization technique and optimize the defrost duct system to meet the performance requirements through robust optimization Design for Six Sigma (DFSS) methodology to reduce the design time, cost, size and weight of the system. Parametric modelling technique is used for designing the defrost duct through design software to reduce the design time for simulation. A 3-dimensional model (3D) of a car cabin with full a HVAC system was developed using Star-CCM+® to predict the performance of the system in the windshield. DFSS methodology helps in finding out the optimized design factors of defrost duct to meet the performance targets such as pressure drop, airflow and velocity at windshield aim points simultaneously. The optimized defrost duct design results were compared with the baseline defrost duct design results and the improvement in performance results is achieved by more than 60%.