Thermoelectric waste heat recovery from rotary kiln shell: an experimentally validated transient multiphysics computational model

A significant amount of thermal energy is lost through rotary kiln shells. Recovering this waste heat presents a promising opportunity for sustainable energy generation and efficiency enhancement. The present study proposes a thermoelectric generator (TEGs) based waste heat recovery (WHR) system to generate supplementary power to effectively recover waste heat from the rotary kiln shell. An experimentally validated transient Multiphysics computational model is employed to evaluate the dynamic behaviour of the WHR system. The performance of the system is evaluated by placing the TEG module consisting of series and parallel configured TEG arrays at different axial, circumferential and radial positions around the kiln shell. The axial position of the TEG module varies along the whole kiln length, which is divided into three zones: initial (0–0.33 m), mid-section (0.33–0.66 m), and end zone (0.66–0.99 m), while for circumferential positions, 60, 90, and 120 degree locations are selected. Water at a constant flowrate of 2.5 L/min and an inlet temperature of 28 °C is circulating in the water blocks placed at the cold face of TEGs to dissipate the heat. The findings of the study suggest that the initial zone in the axial direction, the circumferential location at 90 degrees, and the lowered distance in the radial direction as the locations of maximum electric potential and power generation, around the kiln shell. Moreover, the TEG module's thermoelectric conversion efficiency and power density were found to peak in the zone closer to the heat source. The proposed Multiphysics computational model may be used as a benchmark for future kiln heat recovery studies, using a TEG module around the kiln shell.