Methodology for Shower Water Management in Electric Car Applications

All automotive vehicles with enclosed compartments must pass the Shower test standard - IS 11865 (2006). One of the most severe and critical areas of water leakage is “Water entry into HVAC opening”. Excess water flow in high-pressure conditions and seepage during long-time low-pressure conditions could potentially have a significant impact on water entry inside the HVAC suction cutout and subsequently into the cabin. The study clearly indicates that for making leak proof HVAC opening (suction interface), it is crucial for the structure of BIW Plenum, Trim Applique and its sealing components to be robust enough to effectively collect and divert the water during shower test condition. This robustness is necessary to ensure leakage prevention thru HVAC cutout in varying rain scenarios during customer usage of the vehicle. A systematic approach is followed for assessing leak tightness of the HVAC area. 1. CFD simulation performed to verify the flow path of water during shower test. It is also assessed for the leakage areas. All these areas have been addressed through design countermeasures. 2. Vehicle level shower test done as per the IS 11865 (2006) to evaluate the design. By using endoscope, the leakage areas have been identified. 3. Above 2 have given an understanding of the limitations of CFD tool and the necessity to back it up with test data. 4. The HVAC openings given on plenum applique are important for the HVAC performance. If these openings are higher, it will increase the volume of water entering plenum area and if it is lower, it will increase the HVAC suction pressure drop and reduce AC performance. Hence, this needs to be optimized meeting both HVAC performance and water draining. 5. Further improvements done in the hardware based on above investigation and the HVAC area is made leak proof.