A preliminary study of the effect of groundwater flow on the thermal front created by borehole heat exchangers

Tolooiyan, Ali; Hemmingway, Phil

doi:10.1093/ijlct/cts077

Cited by 10 publications

(4 citation statements)

References 19 publications

(12 reference statements)

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“…Therefore, although it was shown in Figure 6 that the groundwater flow angle influenced the total cost of the system (especially at high values of Pe ), the net gain that could be obtained by choosing the optimal orientation appears to be small compared to the order of magnitude of the total cost of the system. This result can appear to be somewhat different from what previous studies focusing on heat transfer around boreholes in the presence of groundwater flows have concluded [10], [11], [32], i.e., that the orientation of the groundwater flow greatly influences the heat transfer performance and the outlet fluid temperature of the borefield. However, this influence appears to be relatively low on the total cost, as discussed previously.…”

Section: W•m -1 K -1 and N = 20 Yearscontrasting

confidence: 98%

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Influence of groundwater flow on cost minimization of ground coupled heat pump systems

2018

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This paper introduces a new sizing methodology for ground coupled heat pump (GCHP) systems which takes into account groundwater flow (by using G-functions based on analytical models) in order to achieve an economic optimization of the total cost of the project. The procedure includes the calculation of the initial and the annual operational costs. Optimal design variables (boreholes depth, distance between consecutive boreholes, etc.) and borefield layouts (number of boreholes in the x -direction) are presented for different values of the thermal conductivity of the ground. In addition, a parametric study is done to measure the impact of the groundwater flow velocity and angle with respect to the borefield on the economics of the project. It is shown that the effects of the groundwater flow velocity on total cost become apparent only for high velocities, i.e.,

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Section: W•m -1 K -1 and N = 20 Yearscontrasting

confidence: 98%

“…However, groundwater is commonly found in many geological environments. Groundwater flow can significantly affect heat transfer around boreholes [7]- [11]. Many analytical models have been developed to quantify its effects [12]- [16].…”

Section: Introductionmentioning

confidence: 99%

Influence of groundwater flow on cost minimization of ground coupled heat pump systems

2018

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“…The increase in popularity of geothermal source heat pumps may create future problems regarding the space available for new ground sources and the negative influence of neighbouring heat exchangers and their arrays on each other [7]. Therefore, evaluating of the thermal impact is crucial for high-density Ground Source Heat Pumps (GSHP) [8].…”

Section: Introductionmentioning

confidence: 99%

Finite Element Modeling of Geothermal Source of Heat Pump in Long-Term Operation

2020

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Model simulation allows to present the time-varying temperature distribution of the ground source for heat pumps. A system of 25 double U-shape borehole heat exchangers (BHEs) in long-term operation and three scenarios were created. In these scenarios, the difference between balanced and non-balanced energy load was considered as well as the influence of the hydrogeological factors on the temperature of the ground source. The aim of the study was to compare different thermal regimes of BHEs operation and examine the influence of small-scale and short-time thermal energy storage on ground source thermal balance. To present the performance of the system according to geological and hydrogeological factors, a Feflow® software (MIKE Powered by DHI Software) was used. The temperature for the scenarios was visualized after 10 and 30 years of the system’s operation. In this paper, a case is presented in which waste thermal energy from space cooling applications during summer months was used to upgrade thermal performance of the ground (geothermal) source of a heat pump. The study shows differences in the temperature in the ground around different Borehole Heat Exchangers. The cold plume from the not-balanced energy scenario is the most developed and might influence the future installations in the vicinity. Moreover, seasonal storage can partially overcome the negative influence of the travel of a cold plume. The most exposed to freezing were BHEs located in the core of the cold plumes. Moreover, the influence of the groundwater flow on the thermal recovery of the several BHEs is visible. The proper energy load of the geothermal source heat pump installation is crucial and it can benefit from small-scale storage. After 30 years of operation, the minimum average temperature at 50 m depth in the system with waste heat from space cooling was 2.1 °C higher than in the system without storage and 1.6 °C higher than in the layered model in which storage was not applied.

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“…In cases of multiple boreholes interacting with groundwater, the interference between BHEs and its consequent impact on whole system thermal performance becomes relevant. Tolooiyan and Hemmingway () modeled single and 4 × 1 BHEs with unbalanced heating load under pure conduction and mixed conduction‐advection (with 1.85 × 10 −6 m/s groundwater velocity perpendicular to the array axis) regimes; their results show reduction in ground temperature disturbance around the BHE(s) as a result of groundwater flow. Zanchini et al () modeled one, two, and four staggered lines of infinite BHEs with unbalanced heating load and found that even a modest 6 × 10 −8 m/s groundwater velocity (Pé = 0.02) reduces the thermal disturbance and accelerates reaching steady state conditions.…”

Section: Introductionmentioning

confidence: 99%

Impact of Groundwater Flow and Energy Load on Multiple Borehole Heat Exchangers

2014

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The effect of array configuration, that is, number, layout, and spacing, on the performance of multiple borehole heat exchangers (BHEs) is generally known under the assumption of fully conductive transport. The effect of groundwater flow on BHE performance is also well established, but most commonly for single BHEs. In multiple-BHE systems the effect of groundwater advection can be more complicated due to the induced thermal interference between the boreholes. To ascertain the influence of groundwater flow and borehole arrangement, this study investigates single- and multi-BHE systems of various configurations. Moreover, the influence of energy load balance is also examined. The results from corresponding cases with and without groundwater flow as well as balanced and unbalanced energy loads are cross-compared. The groundwater flux value, 10(-7) m/s, is chosen based on the findings of previous studies on groundwater flow interaction with BHEs and thermal response tests. It is observed that multi-BHE systems with balanced loads are less sensitive to array configuration attributes and groundwater flow, in the long-term. Conversely, multi-BHE systems with unbalanced loads are influenced by borehole array configuration as well as groundwater flow; these effects become more pronounced with time, unlike when the load is balanced. Groundwater flow has more influence on stabilizing loop temperatures, compared to array characteristics. Although borehole thermal energy storage (BTES) systems have a balanced energy load function, preliminary investigation on their efficiency shows a negative impact by groundwater which is due to their dependency on high temperature gradients between the boreholes and surroundings.

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A preliminary study of the effect of groundwater flow on the thermal front created by borehole heat exchangers

Cited by 10 publications

References 19 publications

Influence of groundwater flow on cost minimization of ground coupled heat pump systems

Influence of groundwater flow on cost minimization of ground coupled heat pump systems

Finite Element Modeling of Geothermal Source of Heat Pump in Long-Term Operation

Impact of Groundwater Flow and Energy Load on Multiple Borehole Heat Exchangers

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