Design optimization for overhead ventilation duct system for a train using computational fluid dynamics and design of experiment

The overhead multiple outlets ventilation duct system of 18m long is used to maintain the specified indoor thermal comfort environment for each railway passenger car. Therefore, the flow uniformity of the overhead ventilation duct system is very important for heating, ventilation, and air conditioning performance of a train. In this study, design optimization was conducted to increase the flow uniformity of the overhead ventilation duct system for a train by combining computational fluid dynamics and design of experiment methods. To perform the study, the flow uniformity of the base model was evaluated using numerical analysis whose reliability was verified. Design parameters of the overhead ventilation duct system were selected, and an effectiveness evaluation was performed for each design parameter by using 2(k) factorial design. Based on the results of the effectiveness evaluation for the design parameters, optimum models having improved flow uniformity were designed using the response surface method. The performances of the optimum models were also evaluated by the same numerical analysis that was applied to the base model. The flow uniformity of the optimum models was improved by controlling the opening ratios of the perforated plates and guide vane shape. In addition, nonuniform flow components locally existing in the base model were suppressed.