Study of Fluid Flow in Automotive HVAC Ducts and Vents

The HVAC system of a vehicle plays a very important role in ensuring optimal thermal comfort for the passengers. In addition to maintaining the optimal temperature field in the cabin, the passenger must be able to choose the volume and direction of the flow as per their preference. Further, the pressure losses, particularly through the ducts and the vent of the system, must be minimized to ensure minimal energy consumption. This thesis aims to study these pressure losses, and quantify the effects of secondary turbulent structures that develop within them. To do so, new modelling workflows were proposed and developed with three different turbulence modelling approaches (RANS, URANS and DES). Given the importance of the mesh definition in the DES and LES models, three meshing approaches were developed and tested to create a streamlined workflow, with varying degrees of success. These models were benchmarked against a new experimental setup, as well as with the existing computational models in use today, and were found to provide a more reasonable fit with the former. However, the RANS models were found to be incapable of capturing the transient flow phenomena, which led to an underprediction of the total pressure drops by over 10% as compared to the DES model.