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On the Limitations and Implications of Modeling Heat Transport in Porous Aquifers by Assuming Local Thermal Equilibrium

Gossler, Manuel A.; Bayer, Peter; Rau, Gabriel C.; Einsiedl, Florian; Zosseder, Kai

Abstract:
Heat transport in natural porous media, such as aquifers or streambeds, is generally modeled assuming local thermal equilibrium (LTE) between the fluid and solid phases. Yet, the mathematical and hydrogeological conditions and implications of this simplification have not been fully established for natural porous media. To quantify the occurrence and effects of local thermal disequilibrium during heat transport, we systematically compared thermal breakthrough curves from a LTE with those calculated using a local thermal nonequilibrium (LTNE) model, explicitly allowing for different temperatures in the fluid and solid phases. For the LTNE model, we developed a new correlation for the heat transfer coefficient representative of the conditions in natural porous aquifers using six published experimental results. By conducting an extensive parameter study (>50,000 simulations), we show that LTNE effects do not occur for grain sizes smaller than 7 mm or for groundwater flow velocities that are slower than 1.6 m day(-1). The limits of LTE are likely exceeded in gravel aquifers or in the vicinity of pumped bores. For such aquifers, the use of a LTE model can lead to an underestimation of the effective thermal dispersion by a factor of up to 30 or higher, while the advective thermal velocity remains unaffected for most conditions. ... mehr

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Verlagsausgabe §
DOI: 10.5445/IR/1000124000
Veröffentlicht am 26.03.2021
Originalveröffentlichung
DOI: 10.1029/2020WR027772
Dimensions
Zitationen: 4
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Angewandte Geowissenschaften (AGW)
KIT-Zentrum Klima und Umwelt (ZKU)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 10.2020
Sprache Englisch
Identifikator ISSN: 0043-1397, 1944-7973
KITopen-ID: 1000124000
Erschienen in Water resources research
Verlag American Geophysical Union (AGU)
Band 56
Heft 10
Seiten Art.Nr.e2020WR027772
Projektinformation SubTideTools (EU, H2020, 835852)
Vorab online veröffentlicht am 25.09.2020
Schlagwörter local thermal nonequilibrium; thermal dispersion; modeling advective heat transport; local thermal equilibrium; porous aquifer
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