Evaluation of Inlet Temperature Impacts on Heat Transfer and Soil Thermal Behavior in Horizontal Spiral Ground Heat Exchangers

A. Elsherief, Abdelrahman; M Reda, ِAhmed; M Eltohamy, Ahmed; G. Hafez, Ali; Madkour, Hany; M. Khodary, Safia

doi:10.21608/ijaes.2025.373655.1037

Evaluation of Inlet Temperature Impacts on Heat Transfer and Soil Thermal Behavior in Horizontal Spiral Ground Heat Exchangers

Document Type : Original papers

Authors

¹ Department of Civil Engineering Faculty of Engineering Aswan University and Nahda University Aswan and Beni Suef, Egypt

² Department of Mechanical Engineering Faculty of Energy Engineering Aswan university Aswan, Egypt

³ Department of Civil Engineering Faculty of Engineering Beni Suef university Beni Suef, Egypt

⁴ Seismology Department, National Research Institute of Astronomy and Geophysics (NRIAG), Helwan 11421, Egypt Control and Computer Department, College of Engineering, Almaaqal University, Basrah, Iraq. R&D Division, LTLab, Inc.,

⁵ Department of Civil Engineering Faculty of Engineering Aswan University Aswan, Egypt

10.21608/ijaes.2025.373655.1037

Abstract

This study investigates the thermal performance of a Horizontal Spiral Ground Heat Exchanger (HSGHE) under varying inlet temperatures in hot climates, with a focus on ground source heat pumps (GSHPs) as a sustainable energy solution. The experimental setup utilized a spiral tube embedded in dry sand placed within a controlled environment. The results indicated that inlet temperature significantly influences heat exchange rates (HER). Higher inlet temperatures initially resulted in higher HER, but these values declined over time due to the diminishing temperature gradient between the circulating fluid and surrounding soil. For an inlet temperature of 50°C, reductions in HER of approximately 40% and 63% were observed at 45°C and 40°C, respectively. After six hours, HER decreased by 58%, 50%, and 36% for 50°C, 45°C, and 40°C, respectively. These findings highlight the long-term impact of inlet temperature on system efficiency, where higher initial HER does not always correlate with sustained high performance.

The study also assessed soil thermal dispersion and found that heat dissipation was highly localized. For 50°C, the thermal effect extended up to 0.4 meters, while at 45°C, it diminished to 0.3 meters, and at 40°C, the effect was minimal beyond a short distance. Based on these results, an optimal spacing of 0.8 meters between exchangers is recommended to minimize thermal interference and maximize system efficiency. These findings underscore the importance of temperature gradients and operational parameters in optimizing ground heat exchanger performance in hot climates.

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