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Heat exchange and thermal interactions of twin energy tunnels in sand.

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Title: Heat exchange and thermal interactions of twin energy tunnels in sand.
Authors: Magdy, Alaaeldin1 (AUTHOR) Alaaeldin.ogail@univ-lille.fr, Di Donna, Alice2 (AUTHOR) Alice.di-donna@univ-grenoble-alpes.fr, Mroueh, Hussein1 (AUTHOR) Hussein.mroueh@univ-lille.fr
Source: Tunneling & Underground Space Technology. Dec2025, Vol. 166, pN.PAG-N.PAG. 1p.
Subjects: Heat exchangers, Groundwater flow, Thermal conductivity, Smoke plumes, Computer simulation, Tunnel design & construction
Abstract: • The thermal performance of twin energy tunnels in sand is studied. • The effect of groundwater velocity, groundwater level and clear distance on the heat exchange efficiency are investigated. • The thermal plumes and thermal recharge are analysed. • The thermal performance of twin energy tunnels over three years thermal operations is evaluated. • A comparison with the single tunnel thermal performance is presented. In recent years, energy tunnels have gained significant attention as sustainable solution for heating and cooling demands in urban environments. Meanwhile, with the increasing demand for underground space, twin tunnel configurations are often adopted to optimize space utilization and accommodate dense city infrastructures. Therefore, this paper investigates the thermal performance of twin energy tunnels operating simultaneously. A numerical model, based on an approach validated against field test results of Turin Metro line 1, was developed to study the influence of groundwater flow velocity, groundwater level, and clear distance on heat exchange rates and thermal interactions of twin energy tunnels embedded in sand. The results show that when tunnels are fully submerged under the ground water table, the thermal plumes induced by the upstream tunnel decrease the heat exchange efficiency of the downstream tunnel. This decreasing efficiency continues to increase with increasing groundwater flow velocity up to 0.5 m/d. Beyond this velocity, the growing influence of thermal recharge becomes more significant, reducing the thermal plumes effect of one tunnel to the other. At the same time, a smaller clear distance results in higher thermal interactions and consequently lower efficiency of the downstream tunnel. Additionally, the optimal clear distance was observed to significantly depend on groundwater flow velocity. The influence of thermal plumes of the upstream tunnel become less significant when the groundwater level at or below the tunnel invert. The performance of both tunnels was found to remain consistent over three years of thermal operations, and this is attributed to groundwater flow and sufficient recovery periods. [ABSTRACT FROM AUTHOR]
Copyright of Tunneling & Underground Space Technology is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: Engineering Source
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Header DbId: egs
DbLabel: Engineering Source
An: 189146070
AccessLevel: 6
PubType: Academic Journal
PubTypeId: academicJournal
PreciseRelevancyScore: 0
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  Label: Title
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  Data: Heat exchange and thermal interactions of twin energy tunnels in sand.
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  Data: <searchLink fieldCode="AR" term="%22Magdy%2C+Alaaeldin%22">Magdy, Alaaeldin</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> Alaaeldin.ogail@univ-lille.fr</i><br /><searchLink fieldCode="AR" term="%22Di+Donna%2C+Alice%22">Di Donna, Alice</searchLink><relatesTo>2</relatesTo> (AUTHOR)<i> Alice.di-donna@univ-grenoble-alpes.fr</i><br /><searchLink fieldCode="AR" term="%22Mroueh%2C+Hussein%22">Mroueh, Hussein</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> Hussein.mroueh@univ-lille.fr</i>
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  Data: <searchLink fieldCode="JN" term="%22Tunneling+%26+Underground+Space+Technology%22">Tunneling & Underground Space Technology</searchLink>. Dec2025, Vol. 166, pN.PAG-N.PAG. 1p.
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  Data: <searchLink fieldCode="DE" term="%22Heat+exchangers%22">Heat exchangers</searchLink><br /><searchLink fieldCode="DE" term="%22Groundwater+flow%22">Groundwater flow</searchLink><br /><searchLink fieldCode="DE" term="%22Thermal+conductivity%22">Thermal conductivity</searchLink><br /><searchLink fieldCode="DE" term="%22Smoke+plumes%22">Smoke plumes</searchLink><br /><searchLink fieldCode="DE" term="%22Computer+simulation%22">Computer simulation</searchLink><br /><searchLink fieldCode="DE" term="%22Tunnel+design+%26+construction%22">Tunnel design & construction</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: • The thermal performance of twin energy tunnels in sand is studied. • The effect of groundwater velocity, groundwater level and clear distance on the heat exchange efficiency are investigated. • The thermal plumes and thermal recharge are analysed. • The thermal performance of twin energy tunnels over three years thermal operations is evaluated. • A comparison with the single tunnel thermal performance is presented. In recent years, energy tunnels have gained significant attention as sustainable solution for heating and cooling demands in urban environments. Meanwhile, with the increasing demand for underground space, twin tunnel configurations are often adopted to optimize space utilization and accommodate dense city infrastructures. Therefore, this paper investigates the thermal performance of twin energy tunnels operating simultaneously. A numerical model, based on an approach validated against field test results of Turin Metro line 1, was developed to study the influence of groundwater flow velocity, groundwater level, and clear distance on heat exchange rates and thermal interactions of twin energy tunnels embedded in sand. The results show that when tunnels are fully submerged under the ground water table, the thermal plumes induced by the upstream tunnel decrease the heat exchange efficiency of the downstream tunnel. This decreasing efficiency continues to increase with increasing groundwater flow velocity up to 0.5 m/d. Beyond this velocity, the growing influence of thermal recharge becomes more significant, reducing the thermal plumes effect of one tunnel to the other. At the same time, a smaller clear distance results in higher thermal interactions and consequently lower efficiency of the downstream tunnel. Additionally, the optimal clear distance was observed to significantly depend on groundwater flow velocity. The influence of thermal plumes of the upstream tunnel become less significant when the groundwater level at or below the tunnel invert. The performance of both tunnels was found to remain consistent over three years of thermal operations, and this is attributed to groundwater flow and sufficient recovery periods. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Tunneling & Underground Space Technology is the property of Pergamon Press - An Imprint of Elsevier Science and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
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    Identifiers:
      – Type: doi
        Value: 10.1016/j.tust.2025.106958
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      – Code: eng
        Text: English
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      Pagination:
        PageCount: 1
        StartPage: N.PAG
    Subjects:
      – SubjectFull: Heat exchangers
        Type: general
      – SubjectFull: Groundwater flow
        Type: general
      – SubjectFull: Thermal conductivity
        Type: general
      – SubjectFull: Smoke plumes
        Type: general
      – SubjectFull: Computer simulation
        Type: general
      – SubjectFull: Tunnel design & construction
        Type: general
    Titles:
      – TitleFull: Heat exchange and thermal interactions of twin energy tunnels in sand.
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          Name:
            NameFull: Magdy, Alaaeldin
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            NameFull: Di Donna, Alice
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            NameFull: Mroueh, Hussein
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          Dates:
            – D: 01
              M: 12
              Text: Dec2025
              Type: published
              Y: 2025
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              Value: 166
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