scholarly journals Can Borehole Heat Exchangers Trigger Cross-Contamination between Aquifers?

Water ◽  
2020 ◽  
Vol 12 (4) ◽  
pp. 1174 ◽  
Author(s):  
Alessandro Casasso ◽  
Natalia Ferrantello ◽  
Simone Pescarmona ◽  
Carlo Bianco ◽  
Rajandrea Sethi
Keyword(s):  
Contaminant Transport ◽  
Heat Exchangers ◽  
Cross Contamination ◽  
Key Factors ◽  
Permeable Material ◽  
Deep Aquifer ◽  
Analytical Formulas ◽  
Preferential Pathways ◽  
Borehole Heat Exchangers ◽  
Good Agreement

Borehole heat exchangers (BHEs) commonly reach depths of several tens of meters and cross different aquifers. Concerns have been raised about the possibility of boreholes to act as preferential pathways for contaminant transport among aquifers (cross-contamination). This article employs numerical modelling of contaminant transport in the subsurface to address these concerns. A common hydrogeological setup is simulated, composed of three layers: A shallow contaminated and a deep uncontaminated aquifer separated by an aquitard, all crossed by a permeable borehole. The hydraulic conductivity of the borehole and, to a lesser extent, the vertical hydraulic gradient between the aquifers are the key factors of cross-contamination. Results of the numerical simulations highlight that, despite the severe conditions hypothesized in our modelling study, the cross-contamination due to the borehole is negligible when filled with a slightly permeable material such as a geothermal grout properly mixed and injected. A good agreement was found with analytical formulas used for estimating the flow rate leaking through the borehole and for studying the propagation of leaked contaminant into the deep aquifer.

scholarly journals New calculation method for tube cross-flow heat exchangers

2021 ◽  
Vol 323 ◽  
pp. 00032
Author(s):  
Katarzyna Węglarz ◽  
Dawid Taler ◽  
Jan Taler ◽  
Mateusz Marcinkowski
Keyword(s):  
Heat Exchangers ◽  
Cross Flow ◽  
Analytical Models ◽  
Temperature Dependent ◽  
Flow Tube ◽  
Thermal Calculations ◽  
Analytical Formulas ◽  
Flow Heat ◽  
Control Volumes ◽  
Good Agreement

A new method for thermal calculations of the cross-flow tube heat exchangers was proposed. The temperature of both fluids and the wall temperature are determined. The heat exchanger is divided into control volumes, in which outlet fluid temperatures are calculated by closed analytical formulas. Two examples of the application of the method for the calculation of two-pass cross-co-current and cross-countercurrent superheaters were presented. An exact analytical model was also developed for both superheaters to estimate the accuracy of the proposed method. The results of the superheater calculations using the developed method are in good agreement with the results obtained by the exact analytical models. The proposed method can be used to calculate heat exchangers with a complicated flow system in which the physical properties of fluids are temperature-dependent.

Borehole Heat Exchangers in aquifers: simulation of the grout material impact

2016 ◽  
Vol 41 ◽  
pp. 268-271
Author(s):  
Luca Alberti ◽  
Adriana Angelotti ◽  
Matteo Antelmi ◽  
Ivana La Licata
Keyword(s):  
Heat Exchangers ◽  
Borehole Heat Exchangers

scholarly journals Low enthalpy geothermal energy: borehole heat exchangers (BHE). Geological and geothermal supervision during active construction in support of the energy certification of buildings - ESBE certification plan

2012 ◽  
Author(s):  
Lorenzo Cadrobbi ◽  
Fioroni Daniele ◽  
Alessandro Bozzoli
Keyword(s):  
Energy Conservation ◽  
Heat Exchangers ◽  
Energy Efficient ◽  
Geothermal Energy ◽  
Energy Requirements ◽  
Effective Coverage ◽  
Correct Execution ◽  
Environmental Technologies ◽  
Borehole Heat Exchangers ◽  
Ongoing Monitoring

This article draws on the experience matured while working with low-enthalpy geothermic installations both in the design and executive phase as well as ongoing monitoring, within the scope of energy conservation as it relates to building and construction. The goal is to illustrate the feasibility of adopting the ESBE certification protocol (Certification of Energy Efficient Low-Enthalpy Probes) aimed at optimizing the harnessing of local geothermic resources to satisfy the energy requirements of a building, measured against the initial investment. It is often the case, in fact, that during the course of a construction project for a given low-enthalpy installation, we verify incompa tibilities with the local geologic and geothermic models, which, if inadequate during construction, can compromise the proper functioning of the installation and its subsequent operation. To this end, the ESBE method, which adheres to the governing environmental regulations, and which takes its cue from technical statutes within the sector, permits us to validate via verification, simulations and tests, the geothermic field probes used in construction in an objective and standardized manner, thereby joining and supporting the most recent protocols for energy certification of buildings (LEED 2010, CASACLIMA 2011, UE 20120/31 Directive). ESBE certification operates through a dedicated Certifying Entity represented by the REET unit (Renewable Energies and Environmental Technologies) of FBK (Bruno Kessler Foundation) of Trento. The results obtained by applying the ESBE method to two concrete cases, relative to two complex geothermic systems, demonstrate how this protocol is able to guarantee, beyond the correct execution in the field of geothermic probes, an effective coverage of the energy requirements of the building during construction adopting the best optimization measures for the probes in keeping with the local geological and geothermic model.

scholarly journals Geothermal Boreholes in Poland—Overview of the Current State of Knowledge

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3251
Author(s):  
Tomasz Sliwa ◽  
Aneta Sapińska-Śliwa ◽  
Andrzej Gonet ◽  
Tomasz Kowalski ◽  
Anna Sojczyńska
Keyword(s):  
Heat Exchangers ◽  
Oil And Gas ◽  
Produced Water ◽  
Geothermal Water ◽  
Laboratory System ◽  
Water Production ◽  
Injection Wells ◽  
Geological Conditions ◽  
Geothermal Wells ◽  
Borehole Heat Exchangers

Geothermal energy can be useful after extraction from geothermal wells, borehole heat exchangers and/or natural sources. Types of geothermal boreholes are geothermal wells (for geothermal water production and injection) and borehole heat exchangers (for heat exchange with the ground without mass transfer). The purpose of geothermal production wells is to harvest the geothermal water present in the aquifer. They often involve a pumping chamber. Geothermal injection wells are used for injecting back the produced geothermal water into the aquifer, having harvested the energy contained within. The paper presents the parameters of geothermal boreholes in Poland (geothermal wells and borehole heat exchangers). The definitions of geothermal boreholes, geothermal wells and borehole heat exchangers were ordered. The dates of construction, depth, purposes, spatial orientation, materials used in the construction of geothermal boreholes for casing pipes, method of water production and type of closure for the boreholes are presented. Additionally, production boreholes are presented along with their efficiency and the temperature of produced water measured at the head. Borehole heat exchangers of different designs are presented in the paper. Only 19 boreholes were created at the Laboratory of Geoenergetics at the Faculty of Drilling, Oil and Gas, AGH University of Science and Technology in Krakow; however, it is a globally unique collection of borehole heat exchangers, each of which has a different design for identical geological conditions: heat exchanger pipe configuration, seal/filling and shank spacing are variable. Using these boreholes, the operating parameters for different designs are tested. The laboratory system is also used to provide heat and cold for two university buildings. Two coefficients, which separately characterize geothermal boreholes (wells and borehole heat exchangers) are described in the paper.

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