Chiozzi, P.

Giuli, G.

Invernizzi, C.

Pacetti, C.

Verdoya, M.

English

C. Pacetti

G. Giuli

C. Invernizzi

P. Chiozzi

M. Verdoya

Archivio istituzionale della ricerca - Università di Genova

Geophysical Research AbstractsVol. 19, EGU2017-12713, 2017EGU General Assembly 2017© Author(s) 2017. CC Attribution 3.0 License.Thermophysical parameters from laboratory measurements and tests inborehole heat exchangersChiara Pacetti (1), Gabriele Giuli (1), Chiara Invernizzi (1), Paolo Chiozzi (2), and Massimo Verdoya (2)(1) Università di Camerino, Scuola di Scienze e Tecnologie, Camerino, Italy, (2) Università di Genova, DISTAV, Genova, ItalyBesides the type of thermal regime, the performance of borehole heat exchangers relies on the overall thermal resis-tance of the borehole. This parameter strongly depends on the underground thermal conductivity, which accountsfor most of the heat that can be extracted. The geometric configuration and the increase of thermal conductivityof the grout filling back the bore can yield a non-negligible enhancement in thermal performances. In this paper,we present a study on a pilot geothermal plant consisting of two borehole heat exchangers, 95 m deep and 9 mapart. Laboratory and in situ tests were carried out with the aim of investigating underground thermal properties,mechanisms of heat transfer and thermal characteristics of the filling grouts. Samples of grouting materials wereanalysed in the lab for assessing the thermal conductivity. An attempt to improve the thermal conductivity wasmade by doping grouts with alumina. Results showed that alumina large concentrations can increase the thermalconductivity by 25-30%. The in situ experiments included thermal logs under conditions of thermal equilibriumand thermal response tests (TRTs). The analysis of the temperature-depth profiles, based on the mass and energybalance in permeable horizons with uniform thermo-hydraulic and steady-state conditions, revealed that the under-ground thermal regime is dominated by conduction. TRTs were performed by injecting a constant heat rate per unitlength into the boreholes for 60-90 hours. After TRTs, the temperature drop off (TDO) was recorded at 20-m-depthintervals for one week in both holes. The TRT time series were interpreted according to the classical model of theinfinite line source (ILS), to infer the underground thermal conductivity. The TDO records allowed the inferenceof the underground thermal properties variation with depth. The results of thermal conductivity inferred with theILS method are consistent with the values obtained from the TDO analysis.

Thermophysical parameters from laboratory measurements and tests in borehole heat exchangers

https://iris.unige.it/bitstream/11567/893725/1/EGU2017-12713.pdf

Thermophysical parameters from laboratory measurements and tests in borehole heat exchangers

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Archivio istituzionale della ricerca - Università di Genova