Thermal and Thermomechanical Performance of Energy Piles with Double U-Loop and Spiral Loop Heat Exchangers
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 145, Issue 12
Abstract
This study investigates the thermal and thermomechanical behavior of two energy piles with either double U-loop or spiral loop heat exchanger configurations. The piles were installed in a sandstone formation, and a heating-recovery-cooling-recovery cycle was applied to the piles. In both piles, the shaft resistance evaluated from the measured axial-strain distributions was greater in the heating mode than that in the cooling mode. In the heating model, radial expansion was detected. The radial stress at the pile–soil interface increased due to the high stiffness of the sandstone, which in turn increased the shaft friction. In the cooling stage, the radial contraction of the pile was measured, which in turn decreased the radial stress at the pile–soil interface. The amount of pile contraction was similar to the thermally induced free contraction, and consequently large pile settlement was measured at the top of the pile during cooling. The normalized heat-transfer rate shows similar thermal efficiency between heating and cooling, indicating the heat transfer was not much affected by the radial expansion and contract of the piles.
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Data Availability Statement
Some or all data, models, or code generated or used during the study are available from the corresponding author by request.
Acknowledgments
The authors would like to express their gratitude to the National Natural Science Foundation of China (NSFC) for providing financial support of this work (Authorized No. 41502238). The project was also supported by the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan) No. CUGL150818. The funding provided by China Scholarship Council (CSC) during a visit to the University of California, Berkeley, is deeply appreciated.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 145 • Issue 12 • December 2019
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©2019 American Society of Civil Engineers.
History
Received: Jun 11, 2018
Accepted: Jul 24, 2019
Published online: Sep 28, 2019
Published in print: Dec 1, 2019
Discussion open until: Feb 28, 2020
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