CO ₂ Concentration in the Cabin in the Event of a Leak: CFD Simulation and Testing

CO₂ is an alternative to replace the conventional refrigerant (R134a) for the air-conditioning system, due to the high Global Warming Potential (GWP) of R134a. There are concerns with the use of CO₂ as a refrigerant due to health risks associated with exposure to CO₂, if the concentration of CO₂ is over the acceptable threshold. For applications with CO₂ as the refrigerant, the risk of CO₂ exposure is increased due to the possibility of CO₂ leakage into the cabin through the duct system; this CO₂ is in addition to the CO₂ generated from the respiration of the occupants. The initiation of the leak could be due to a crash event or a malfunction of the refrigerant system. In an automobile, where the interior cabin is a closed volume (with minimal venting), the increase in concentration can be detrimental to the customer but is hard to detect.

In this paper, the concentration of CO₂ in the event of a leak is studied - Computational Fluid Dynamics (CFD) is used to simulate the concentration of CO₂ in the cabin and the results are validated with experimental measurements. A transient simulation showing the increase in concentration of CO₂ in the cabin is conducted as a preliminary demonstration of the usefulness of the CFD tool in cabin CO₂ dispersion - the CFD model is able to accurately capture the trends and values of the CO₂ concentration in the cabin as a function of time.