Thermo-Hydraulic Comparison of Vertical and Horizontal Spiral Ground Heat Exchangers

Growing concerns about the energy crisis and global warming have driven interest in geothermal energy. This paper presents a numerical thermo-hydraulic comparison of spiral ground heat exchangers (SGHEs) in vertical and horizontal configurations. Numerical models were validated against experimental data using ANSYS Fluent 2023 R2. Five spiral pitch values were tested to analyze their impact on heat transfer rate (HTR), pressure drop, and total pipe length. Results showed that decreasing pitch increases HTR but significantly raises pressure drop and pipe length. Higher inlet fluid velocities also increased HTR but led to greater pressure drops. Under all tested conditions, the vertical configuration consistently outperformed the horizontal one, achieving up to 19.3% higher mean HTR. For both configurations, a 10 cm pitch provided the best balance between HTR, pressure drop, and pipe length. Increasing inlet velocity from 0.05 to 0.15 ms−1 increased mean HTR by approximately 30% for both configurations. These findings offer practical guidance for selecting the most appropriate SGHE configuration for specific geothermal applications.