View in EDS

Numerical Analysis of Borehole Heat Exchanger Performance in Shallow Gravel Aquifers and Clay-dominated Soil.

Saved in:
Bibliographic Details
Title: Numerical Analysis of Borehole Heat Exchanger Performance in Shallow Gravel Aquifers and Clay-dominated Soil.
Alternate Title: Numerička analiza učinkovitosti bušotinskoga izmjenjivača topline u plitkim vodonosnicima šljunka i tlu u kojemu dominira glina.
Authors: Brettschneider, Amalia Lekić1 amalia.lekic.brettschneider@rgn.unizg.hr, Perković, Luka1
Source: Rudarsko-Geološko-Naftni Zbornik. 2024, Vol. 39 Issue 2, p75-84. 10p.
Subject Terms: Heat exchangers, Numerical analysis, Gravel, Finite element method, Geothermal wells, Heat transfer, Thermal conductivity, Mass transfer, Aquifers
Abstract (English): The performance of geothermal heat extraction in shallow aquifers depends on both Borehole Heat Exchanger (BHE) and soil or aquifer properties. In this work, an analysis of the thermal yield of a shallow geothermal reservoir was made numerically with the finite element method used to simulate heat and mass transfer in the three-dimensional reservoir. The main parameters for analysis which have been considered are the geometry and physical parameters of the BHE and grout, as well as aquifer matrix and groundwater fluid. Physical parameters are thermal conductivity, flow conductivity, expansion coefficient, porosity, volumetric heat capacity, anisotropy and dispersivity. The numerical tests have been performed in single BHE line source configuration representing numerically modelled thermal response test for the estimation of sustainable heat extraction. The domain size was a 100x100 meter rectangle with a depth of 200 meters. Three main lithological configurations have been modelled: gravel aquifer with low and high convection of groundwater fluid, as well as a shallow geothermal reservoir dominated by clay material without convection. For selected cases, the analysis for temporal and spatial discretization was also made. Three-dimensional transient modelling was made in FEFLOW® software with pre- and post-processing done in user-defined Python scripts. The results show the most influential pa)rameters to be considered when setting up the real case simulation of geothermal heating and cooling, as well as optimal temporal and spatial discretization set-up with respect to expected thermal gradients in the reservoir [ABSTRACT FROM AUTHOR]
Abstract (Croatian): Učinkovitost korištenja geotermalne topline u plitkim vodonosnicima ovisi o bušotinskome izmjenjivaču topline (BHE) i svojstvima tla ili vodonosnika. U ovome radu numerički je napravljena analiza osjetljivosti toplinskoga prinosa plitkoga geotermalnog ležišta metodom konačnih elemenata korištenom za simulaciju prijenosa topline i mase u trodimenzionalnome ležištu. Glavni parametri za analizu osjetljivosti koji su uzeti u obzir jesu geometrija i fizički parametri BHE-a i cementne obloge te matrice vodonosnika i podzemne vode. Fizički su parametri toplinska vodljivost, vodljivost protoka, koeficijent ekspanzije, poroznost, volumetrijski toplinski kapacitet, anizotropija i disperzivnost. Numerički testovi provedeni su u konfiguraciji jednoga bušotinskog izmjenjivača topline koji predstavlja numerički modelirani test toplinskoga odziva za procjenu održivoga korištenja topline. Domena je bila pravokutnoga oblika 100 x 100 metara s dubinom od 200 metara. Za svaku analizu osjetljivosti modelirane su tri glavne konfiguracije: šljunčani vodonosnik s niskom i visokom konvekcijom podzemne vode te ležište u kojemu dominira glinoviti materijal bez konvekcije. Za odabrane slučajeve također je napravljena analiza osjetljivosti na vremensku i prostornu diskretizaciju. Trodimenzionalno modeliranje napravljeno je u softveru FEFLOW® uz prethodnu i naknadnu obradu u korisnički definiranim skriptama za Python. Rezultati pokazuju najutjecajnije parametre koje treba uzeti u obzir pri postavljanju stvarne simulacije slučaja grijanja i hlađenja geotermalnim izvorom, kao i optimalnu postavku vremenske i prostorne diskretizacije s obzirom na očekivane toplinske gradijente u ležištu. [ABSTRACT FROM AUTHOR]
Database: Supplemental Index
Description
Abstract:The performance of geothermal heat extraction in shallow aquifers depends on both Borehole Heat Exchanger (BHE) and soil or aquifer properties. In this work, an analysis of the thermal yield of a shallow geothermal reservoir was made numerically with the finite element method used to simulate heat and mass transfer in the three-dimensional reservoir. The main parameters for analysis which have been considered are the geometry and physical parameters of the BHE and grout, as well as aquifer matrix and groundwater fluid. Physical parameters are thermal conductivity, flow conductivity, expansion coefficient, porosity, volumetric heat capacity, anisotropy and dispersivity. The numerical tests have been performed in single BHE line source configuration representing numerically modelled thermal response test for the estimation of sustainable heat extraction. The domain size was a 100x100 meter rectangle with a depth of 200 meters. Three main lithological configurations have been modelled: gravel aquifer with low and high convection of groundwater fluid, as well as a shallow geothermal reservoir dominated by clay material without convection. For selected cases, the analysis for temporal and spatial discretization was also made. Three-dimensional transient modelling was made in FEFLOW® software with pre- and post-processing done in user-defined Python scripts. The results show the most influential pa)rameters to be considered when setting up the real case simulation of geothermal heating and cooling, as well as optimal temporal and spatial discretization set-up with respect to expected thermal gradients in the reservoir [ABSTRACT FROM AUTHOR]
ISSN:03534529
DOI:10.17794/rgn.2024.2.6