Study on performance and layout optimization of buried heat exchangers array in Karst landform

Abstract

Ground source heat pump systems (GSHPs) are a key technology for geothermal energy utilization, and improving their performance supports the global transition to renewable energy. However, the influence of hydrogeological conditions and heat exchanger configuration on the performance of buried heat exchanger arrays (BHEAs) has not been fully explored. This study evaluates the performance of three layouts—rectangular, diamond, and trapezoidal—under varying pipe spacings, particularly under the influence of groundwater seepage. The results show that the diamond layout achieves better thermal equilibrium and heat transfer efficiency, particularly at small pipe spacings. It also outperforms in terms of heat exchange decay rate (HEDR) and thermal disturbance coefficient (TDC) compared to other layouts. Key findings include: (i) The diamond and trapezoidal layouts exhibit significantly lower thermal accumulation and thermal interference under groundwater seepage compared to the rectangular layout. (ii) Regional thermal efficiency (RTE) and average heat transfer increase with pipe spacing, while TDC decreases. (iii) At 2 m pipe spacing, average heat transfer under seepage increased by 20.31 W/m (rectangular), 21.08 W/m (trapezoidal), and 18.67 W/m (diamond) compared to non-seepage condition. (iv) Groundwater seepage increased the maximum RTE by 40 %, reduced the maximum TDC by 1.82 m, and effectively lowered HEDR. These findings highlight the positive impact of groundwater seepage on BHEAs performance and provide valuable insights for the future design and optimization of GSHPs.