A Combined Automotive Exhaust Heat Recovery Technique Using Phase Change Material and Jet Impingement Heat Transfer with Wall Protrusions and Baffle

Automotives play a very important role in day-to-day human lives. The exhaust gas emitted from automotive vehicles of current technologies is one of the major contributions to global temperature increment. It is important to develop a system that can conserve energy and incorporate it into current vehicles which are in use. Phase change materials (PCM) are well known for energy storage applications because of their crucial thermophysical property known as latent heat of fusion. The gas from the exhaust pipe of automobiles can be considered a turbulent jet. With this assumption in this study, a system is proposed by combining jet impingement and phase change material at the exhaust pipe of automobiles to recover the thermal energy which is being let out into the atmosphere as waste. Liquid Gallium is chosen as a phase change material for this study because of its high thermal conductivity nature compared to other hydrocarbon-based phase change materials. Initially, a combined numerical study of jet impingement heat transfer and phase change material is performed and the results are chosen as a benchmark. Later the study extends with the application of flow baffles and wall protrusions to enhance energy conservation. The enhancement study comprises four different baffle designs with two different heights and spacings. Also, two different wall protrusion models with different protrusion wavelengths. The numerical results show that the application of flow baffles promisingly enhances energy recovery. On the other hand, the application of wall protrusion shows a significant increment in energy recovery but it is important to choose the proper wavelength for wall protrusion.