Optimization of injection-port design for multi-level waste heat recovery in an electric vehicle heat pump system

A multi-level waste heat recovery (MWHR) is an effective heat recovery strategy to utilize a limited amount of waste heat in electric vehicles (EVs). Because the MWHR system relies on the vapor injection technique, the port hole design critically affects the system performance. However, none of previous studies presented the optimal design of injection port for MWHR system. In this study, the effect of port design on the MWHR system per-formance was investigated. A continuous injection model was developed to reflect the dynamic behavior of MWHR system and integrated into a transient heat pump model. Integrated thermal management system (ITMS) model was established by combining the transient heat pump model with electric device model. The effects of injection port location and size were analyzed with the ITMS model under cold-start conditions. The optimal port hole design was suggested as the dual port located at 600 degrees with a radius of 2 mm from the perspective of total energy consumption. Total power consumptions were saved up to 12.0 % and 10.6 % with the optimal port size and angle, respectively. This study can provide reference data and an optimization methodology for designing the MWHR system port hole.