Numerical and experimental study of transient conjugate heat transfer in helical closed-loop geothermal heat exchangers for application of thermal energy storage in backfilled mine stopes
The geothermal potential available from deep underground mines has yet to be utilized. However, stope-coupled heat exchangers (SCHE) are aiming to take advantage of the unused low-grade geothermal energy. Backfilled stopes provide a unique opportunity to install nonlinear heat exchangers, as the geo...
| Main Authors: | Templeton, J.D., Ghoreishi-Madiseh, S.A., Hassani, F.P., Sasmito, A.P., Kurnia, J.C. |
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| Format: | Article |
| Institution: | Universiti Teknologi Petronas |
| Record Id / ISBN-0: | utp-eprints.29834 / |
| Published: |
John Wiley and Sons Ltd
2020
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| Online Access: |
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85084148639&doi=10.1002%2fer.5457&partnerID=40&md5=04b407bbeb9151069747c5a2f09f8b22 http://eprints.utp.edu.my/29834/ |
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| Summary: |
The geothermal potential available from deep underground mines has yet to be utilized. However, stope-coupled heat exchangers (SCHE) are aiming to take advantage of the unused low-grade geothermal energy. Backfilled stopes provide a unique opportunity to install nonlinear heat exchangers, as the geometry is not limited to the shape of a borehole. Helical pipes deliver superior fluid mixing and heat exchange compared to straight pipes, due to the effect of the secondary flow within the helical pipe. The helical closed-loop geothermal heat exchanger enables the backfilled stopes of the mine to be repurposed as thermal energy storage units. This article delves into the experimental results from a unique state-of-the-art laboratory scale helical closed-loop heat exchanger with varying thermophysical parameters. Additionally, a novel conjugate numerical model is developed and its results are validated against the base case of the experimental studies. Additionally, the numerical model is validated in a spatial-temporal sense with thermocouple data from the experimental rig. The numerical model is also applied to a helical SCHE situated within a backfilled stope for the first time. The results of the numerical model suggest that the pumping rate through the SCHE has a significant effect on the heat exchange rate and the overall energy transfer between the SCHE and the backfill. Additionally, the temperature contours from the numerical model suggest that a decreased pitch/helical diameter will increase the storage capacity of the helical SCHE. Overall, an average of 2.5 MW can be stored over the first 4 days of geothermal charging with the investigated full-scale SCHE, boasting a pseudo-steady-state storage rate of 1.7 MW. © 2020 John Wiley & Sons Ltd |
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