Thermal Performance of a Preheating Chamber for Convective Heating of Aluminum Blocks

Waste heat recovery is a key strategy for improving the energy efficiency and sustainability of metallurgical processes, in which substantial energy is lost through high-temperature exhaust gases. This study numerically investigates an aluminum-block preheating chamber designed to recover thermal energy from furnace exhaust streams. A three dimensional computational fluid dynamics model was developed to simulate turbulent gas flow and conjugate heat transfer between the exhaust gases and solid aluminum blocks. Two geometric configurations, based on half- and full-block arrangements, and two operating conditions, with the extractor hood open or closed, were compared in terms of flow patterns, temperature distributions, and heat recovery performance. The results demonstrate that both operating conditions and block geometry strongly influence the system’s thermal behavior. Enhanced flow mixing promotes heat transfer, while the full-block configuration increases overall thermal energy absorption through greater interaction with the hot gas stream. The optimal configuration produces a substantial increase in block temperature and recovered energy. An economic assessment based on industrial production data estimates annual natural gas savings worth approximately €25,000.