Investigation of the Thermal Performance of Energy Tunnel Equipped with the Insulation Layer Considering Ventilation and Groundwater Seepage

The insulation layer is usually installed in the tunnel structure, whereas the influence of the insulation layer on the thermal behavior of energy tunnel ground heat exchangers (GHEs) is rarely investigated. The model tests were performed in this study to evaluate the heat transfer potential of the energy tunnel with the insulation layer under ventilation and groundwater seepage. The results can be obtained as follows: first, the fluctuations of air temperature and surrounding rock temperature at different locations are relevant to insulation layer, ventilation, and groundwater seepage. Second, the reduction effect of ventilation on the interface temperature of tunnel lining and surrounding rock is alleviated when using an insulation layer, and the interface temperature at upstream section of groundwater seepage is more easily affected by the energy tunnel GHEs. Third, the variation range of ground temperature is wider at the downstream section of groundwater flow. Moreover, the heat exchange rates of tunnel without the insulation layer improve by 5.82% and 6.45% with increasing wind speed at two groundwater flow velocities of 1 × 10 − 4 and 5 × 10 − 4 m/s, and there are only 2.03% and 0.77% enhancements of heat exchange rates by ventilation for the tunnel with the insulation layer. However, the thermal performance of the energy tunnel improved by groundwater is less relevant to the existence of the insulation layer. The relevant findings can provide an effective guidance for the following research and design of the energy tunnel.

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Experimental Study on the Temperature Field of Cold Region Tunnel under Various Groundwater Seepage Velocities

Advances in Civil Engineering ◽

10.1155/2020/6695099 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Shiding Cao ◽

Taishan Lu ◽

Bo Zheng ◽

Guozhu Zhang

Keyword(s):

Temperature Field ◽

Coupling Effect ◽

Calculation Model ◽

Surrounding Rock ◽

Laboratory Model ◽

Interface Temperature ◽

Cold Region ◽

Seepage Velocity ◽

Groundwater Seepage ◽

Tunnel Cross Section

Groundwater seepage significantly affects the temperature field of a cold region tunnel. Laboratory model tests are carried out to evaluate its effects, yielding four main results. First, groundwater seepage can increase tunnel air temperature and decrease the thickness and length of the tunnel insulation layer. Second, groundwater seepage and tunnel ventilation exert a coupling effect on the surrounding rock temperature. This effect is related to the surrounding rock depth. Third, the influence of the groundwater seepage velocity on the temperature of the interface between the lining and surrounding rock demonstrates a spatial difference, and the groundwater seepage leads to an uneven temperature distribution at the interface between the lining and surrounding rock. Furthermore, under groundwater seepage, the shape and size of the tunnel cross section have significant effects on the interface temperature. Fourth, the cold region tunnel has an antifreezing capability that is mainly related to the frost heaving of the surrounding rock and the groundwater seepage velocity. This capability should be fully utilized in the design of cold region tunnels. The experimental data presented can be used to verify the reliability of the theoretical calculation model for tunnel temperatures in cold regions.

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Groundwater flow simulation and its application in GaoSong ore field, China

Journal of Water and Climate Change ◽

10.2166/wcc.2018.182 ◽

2018 ◽

Vol 10 (2) ◽

pp. 276-284 ◽

Cited By ~ 2

Author(s):

Gang Chen ◽

Shiguang Xu ◽

Chunxue Liu ◽

Lei Lu ◽

Liang Guo

Keyword(s):

Numerical Model ◽

Flow Field ◽

Groundwater Flow ◽

Mine Water ◽

Permeability Coefficient ◽

Water Inrush ◽

Seepage Field ◽

Groundwater Seepage ◽

Calculation Results ◽

Groundwater Flow Field

Abstract Mine water inrush is one of the important factors threatening safe production in mines. The accurate understanding of the mine groundwater flow field can effectively reduce the hazards of mine water inrush. Numerical simulation is an important method to study the groundwater flow field. This paper numerically simulates the groundwater seepage field in the GaoSong ore field. In order to ensure the accuracy of the numerical model, the research team completed 3,724 field fissure measurements in the study area. The fracture measurement results were analyzed using the GEOFRAC method and the whole-area fracture network data were generated. On this basis, the rock mass permeability coefficient tensor of the aquifer in the study area was calculated. The tensor calculation results are used in the numerical model of groundwater flow. After calculation, the obtained numerical model can better represent the groundwater seepage field in the study area. In addition, we designed three different numerical models for calculation, mainly to explore the influence of the tensor assignment of permeability coefficient on the calculation results of water yield of the mine. The results showed that irrational fathom tensor assignment would cause a significant deviation in calculation results.

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Assessment of the Thermal Performance of Data Center; A Case Study in Earth Rangers Centre

10.32920/ryerson.14652369.v1 ◽

2021 ◽

Author(s):

Ladan Vahidi-Arbabi

Keyword(s):

Thermal Performance ◽

Data Center ◽

Data Centers ◽

Model Performance ◽

Energy Model ◽

Actual Case ◽

Excessive Heat ◽

Ground Heat Exchangers ◽

Performance Accuracy

Thermal performance of complex buildings like data centers is not easy to evaluate. Experimental Investigation of the effects of energy conservation methods or any alteration that might occur in hundreds of variables in data centres would cost stakeholders time and money. And they might find worthless at times. Building energy model is a well-established field of science with an insufficient number of applications in data centers. This study presents methods of developing a data center model based on an actual case study. Moreover, it identifies effective calibrating strategies to increase the model performance accuracy relative to a recorded dataset. A reliable energy model can assist data center operators and researchers in different ways. As a result, calibrated energy model proved Earth Rangers’ data center can be independent of a heat pump or chiller use for most of the year, while ground heat exchangers deliver excessive heat to the ground as the heat sink.

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Effects of the Circuit Arrangement on the Thermal Performance of Double U-Tube Ground Heat Exchangers

Energies ◽

10.3390/en13123275 ◽

2020 ◽

Vol 13 (12) ◽

pp. 3275

Author(s):

Aminhossein Jahanbin ◽

Giovanni Semprini ◽

Andrea Natale Impiombato ◽

Cesare Biserni ◽

Eugenia Rossi di Schio

Keyword(s):

Thermal Resistance ◽

Thermal Performance ◽

Numerical Code ◽

Geometrical Parameters ◽

Fluid Temperature ◽

The Finite Element Method ◽

Ground Heat Exchangers ◽

Borehole Thermal Resistance ◽

The Impact ◽

Circuit Configuration

Given that the issue of variations in geometrical parameters of the borehole heat exchanger (BHE) revolves around the phenomenon of thermal resistance, a thorough understanding of these parameters is beneficial in enhancing thermal performance of BHEs. The present study seeks to identify relative changes in the thermal performance of double U-tube BHEs triggered by alterations in circuit arrangements, as well as the shank spacing and the borehole length. The thermal performance of double U-tube BHEs with different configurations is comprehensively analyzed through a 3D transient numerical code developed by means of the finite element method. The sensitivity of each circuit configuration in terms of the thermal performance to variations of the borehole length and shank spacing is investigated. The impact of the thermal interference between flowing legs, namely thermal short-circuiting, on parameters affecting the borehole thermal resistance is addressed. Furthermore, the energy exchange characteristics for different circuit configurations are quantified by introducing the thermal effectiveness coefficient. The results indicate that the borehole length is more influential than shank spacing in increasing the discrepancy between thermal performances of different circuit configurations. It is shown that deviation of the averaged-over-the-depth mean fluid temperature from the arithmetic mean of the inlet and outlet temperatures is more critical for lower shank spacings and higher borehole lengths.

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Modeling of vertical ground heat exchangers in the presence of groundwater flow and underground temperature gradient

Energy and Buildings ◽

10.1016/j.enbuild.2019.03.020 ◽

2019 ◽

Vol 192 ◽

pp. 15-30 ◽

Cited By ~ 8

Author(s):

Iosifina Iosif Stylianou ◽

Savvas Tassou ◽

Paul Christodoulides ◽

Lazaros Aresti ◽

Georgios Florides

Keyword(s):

Temperature Gradient ◽

Groundwater Flow ◽

Heat Exchangers ◽

Ground Heat Exchangers ◽

Vertical Ground

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Numerical Analysis of Optimization Design for Insulation Layer in Cold Regions Tunnel

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1065-1069.368 ◽

2014 ◽

Vol 1065-1069 ◽

pp. 368-372 ◽

Cited By ~ 3

Author(s):

He Song ◽

Chao Liang Ye ◽

Jun Feng Mi

Keyword(s):

Optimization Design ◽

Frost Damage ◽

Surrounding Rock ◽

Temperature Fields ◽

Insulation Layer ◽

Cold Region ◽

Element Analysis ◽

Penetration Length ◽

Dimensional Finite Element ◽

Frost Penetration

Setting of insulation layer is widely recognized to prevent frost damage for tunnels constructed in cold region. Optimization design of insulation layers, however, still need deeply investigate. In this paper, taking Houanshan tunnel as example, two-dimensional finite element analysis on the optimization design of insulation layers has been carried out by ABAQUS. The tunnel temperature fields due to various thickness and length of insulation layer are numerically analyzed. It shows that ,1)4.85°C increased at backside of insulation layer with thickness of 5cm, while 5.8°C increased for thickness of 7cm;2) frozen depth of surrounding rock decrease with the increase of insulation layer thickness. The farther distance to tunnel portal, the smaller thickness of insulation layer required to prevent the surrounding rock from freezing;3)According to analysis, frost penetration length should be 450~500m before tunnel holing-through ,while 720m~830m after tunnel holing-through.

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