Strategic Optimization of Operational Parameters in a Low-Temperature Waste Heat Recovery System: A Numerical Approach

In the transition to sustainable energy consumption, waste heat recovery and storage systems become key to advancing Europe’s energy efficiency and reducing carbon emissions, especially by harnessing thermal energy from low-temperature sources like wastewater. This study focuses on optimizing a heat recovery system that uses heat pipes for effective heat extraction and coconut oil as a phase change material for efficient thermal storage. A total of 12 numerical simulations were conducted to analyze the outcomes of varying operational parameters, including the diameter of the heat pipe, condenser size, secondary agent flow rate, coil length, and primary agent inlet temperature. The numerical findings indicate that reduced flow rates, in combination with smaller condenser diameters and increased primary agent temperatures, greatly improve the efficiency of heat absorption and transfer. Following a 4 h test period, the most successful outcome resulted in a melting fraction of 98.8% and a temperature increase of 18.95 °C in the output temperature of the secondary agent. In contrast, suboptimal conditions resulted in only a 2.21 °C rise and a 30.80% melting fraction. The study highlights the importance of component sizing and optimization, noting that strategic modifications and appropriate phase change materials can lead to highly efficient and scalable systems.