CFD simulations of horizontal ground heat exchangers: A comparison among different configurations

Congedo, Paolo Maria; Colangelo, Gianpiero; Starace, Giuseppe

doi:10.1016/j.applthermaleng.2011.09.005

Cited by 258 publications

(126 citation statements)

References 12 publications

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“…The results demonstrated lower consumption of electricity and higher seasonal performance factor when mains water was used. The Research Center for Energy and Environment in Lecce [6] verified the basic configuration of horizontal ground source heat exchangers. Throughout the year the researchers there measured the temperatures of the soil and the thermal output discharged by the heat exchangers.…”

Section: Open Accessmentioning

confidence: 99%

Temperatures and Heat Flows in a Soil Enclosing a Slinky Horizontal Heat Exchanger

2014

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Abstract:Temperature changes and heat flows in soils that host "slinky"-type horizontal heat exchangers are complex, but need to be understood if robust quantification of the thermal energy available to a ground-source heat pump is to be achieved. Of particular interest is the capacity of the thermal energy content of the soil to regenerate when the heat exchangers are not operating. Analysis of specific heat flows and the specific thermal energy regime within the soil, including that captured by the heat-exchangers, has been characterised by meticulous measurements. These reveal that high concentrations of antifreeze mix in the heat-transfer fluid of the heat exchanger have an adverse impact on heat flows discharged into the soil.

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Section: Open Accessmentioning

confidence: 99%

Temperatures and Heat Flows in a Soil Enclosing a Slinky Horizontal Heat Exchanger

2014

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“…The installation depth of the helix, with the bottom lying at 1.0 m and the top at 0.60 m depth, is deliberately chosen, on one hand, to verify if at 0.60 m depth, according to industrial partner experience, the effect of soil thermal conductivity is dominant compared to that of the daily temperature amplitude [26]; on the other, to force the growing and potential merging of the ice radius around the helix and see the reaction of the surrounding soil. In addition, the selected installation depth allows to reduce the installation costs.…”

Section: Test Sitementioning

confidence: 99%

“…and to the local geological and environmental conditions [22][23][24][25]. Recent works have concluded that helical heat exchangers, known as helix systems, provide the best thermal performance compared to common horizontal loop systems, even if they need more tube length [26]. Moreover, they are also a valid alternative to vertical systems installed at shallow depths (up to 25 m) [27][28][29][30].…”

Section: Introductionmentioning

confidence: 99%

Factors Influencing the Thermal Efficiency of Horizontal Ground Heat Exchangers

Sipio

Bertermann

2017

Energies

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Abstract:The performance of very shallow geothermal systems (VSGs), interesting the first 2 m of depth from ground level, is strongly correlated to the kind of sediment locally available. These systems are attractive due to their low installation costs, less legal constraints, easy maintenance and possibility for technical improvements. The Improving Thermal Efficiency of horizontal ground heat exchangers Project (ITER) aims to understand how to enhance the heat transfer of the sediments surrounding the pipes and to depict the VSGs behavior in extreme thermal situations. In this regard, five helices were installed horizontally surrounded by five different backfilling materials under the same climatic conditions and tested under different operation modes. The field test monitoring concerned: (a) monthly measurement of thermal conductivity and moisture content on surface; (b) continuous recording of air and ground temperature (inside and outside each helix); (c) continuous climatological and ground volumetric water content (VWC) data acquisition. The interactions between soils, VSGs, environment and climate are presented here, focusing on the differences and similarities between the behavior of the helix and surrounding material, especially when the heat pump is running in heating mode for a very long time, forcing the ground temperature to drop below 0 • C.

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“…There are still relatively few numerical solutions to the ground heat transfer problem for new GHEs shapes because of their novelty. In [11], the effect of the depth of installation and the soil thermal conductivity on the performance of three different heat exchangers (straight, helical and slinky-coil) is investigated. In [4,12] the commercial code FEFLOW is used to simulate the energy performance of a slinky-coil, taking into account the energy balance at the ground surface and new spatial arrangements, whereas in [5] FEFLOW is implemented to make a comparison between the energy behaviour of a flatpanel and a radiator.…”

Section: Introductionmentioning

confidence: 99%

On the sizing of a flat-panel ground heat exchanger

Bortoloni

Bottarelli

2014

Int J Energy Environ Eng

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Ground-source heat pumps are a reliable technology and may represent an efficient and cost-effective option for space heating and cooling, when the investment for ground heat exchangers is reasonable. New advanced ground exchangers have been recently proposed, showing high performances also in shallow ground; their shape has not yet been investigated in literature. In the present study, an analytical solution based on the line source method is applied for sizing a novel shape. This so-called flat-panel shape is assumed to be an equivalent slinky-coil having the same heat transfer surface per unit of trench length. As overall benchmarks, two other configurations of straight pipes disposed vertically and horizontally have been sized; all devices are supposed to work in a four lined geothermal field. The building heating requirement has been evaluated assuming a simplified lumped system and three different climate zones, defined by 2,000, 2,500 and 3,000 degree days. Then, a 2D finite-element model has been implemented to solve the transient heat conduction problem in the ground. The results of the analytical formulation and numerical simulations have been compared in terms of average temperature at the wall surface of the heat exchanger. The design minimum temperature considered by the analytical method in sizing the two straight pipe configurations and the flat-panel is accurately reproduced by the numerical model. Therefore, the slinky-coil equivalent approach followed in the analytical method for sizing the flat-panel seems to be a reliable and suitable approximation.

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CFD simulations of horizontal ground heat exchangers: A comparison among different configurations

Cited by 258 publications

References 12 publications

Temperatures and Heat Flows in a Soil Enclosing a Slinky Horizontal Heat Exchanger

Temperatures and Heat Flows in a Soil Enclosing a Slinky Horizontal Heat Exchanger

Factors Influencing the Thermal Efficiency of Horizontal Ground Heat Exchangers

On the sizing of a flat-panel ground heat exchanger

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