3D numerical modeling of seawater seepage and heat transfer in beach well for seawater source heat pump: Effects of well and aquifer parameters on seawater level and temperature

The seawater source heat pump (SWHP) system efficiently uses ocean energy to supply heating and cooling for coastal buildings. The design of beach wells employed in SWHP systems not only affects the temperature of extracted seawater and fluctuations in coastal groundwater levels but may also compromise the stability of geological formations under extremely high water extraction flow rates. To reveal the mechanisms of seepage flow and heat transfer, this study developed a three-dimensional porous media seepage and heat transfer model based on COMSOL Multiphysics, systematically investigating the influence of key parameters—such as well depth, well-to-coastline distance, well radius, and aquifer thickness—on the seepage field and temperature distribution. The results indicate that the well water level drawdown decreased with increasing well depth, well radius, and aquifer thickness, and increased with increasing well-to-coastline distance. Additionally, the extracted seawater temperature increased with increasing well depth, well-to-coastline distance, and aquifer thickness. Specifically, well depth exerted the most significant impact on seawater level drawdown: an increase from 20 to 80 m reduced the drawdown by 62.3%, decreasing from 4.72 to 1.78 m. In contrast, aquifer thickness exerted the most significant influence on the temperature of extracted seawater: an increase from 20 to 100 m elevated the minimum temperature by 117.7%, rising from 4.70 to 10.23 °C. The model established in this study provides a theoretical basis for optimizing beach well intake systems, enabling increased pumping rates and enhanced thermal output performance while ensuring the stable operation of the underlying aquifer.