Thermal radiation and conduction properties of materials ranging from sand to rock-fill

FillionMarie-Hélène,; CôtéJean,; KonradJean-Marie,

doi:10.1139/t10-093

Cited by 32 publications

(11 citation statements)

References 28 publications

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“…While the role of radiant heat exchange is generally deemed to be negligible in all but the coarsest of soils (Rees et al, 2000, Fillion et al, 2011, the potential importance of groundwater convection makes the model realistically applicable to cases of low permeability, or dry, soils or rocks. However, if the groundwater at a specific site is known to be in static conditions, the model can be also applied to high permeability water saturated geologic materials.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Influences on the thermal efficiency of energy piles

Cecinato

Loveridge

2015

Energy

128

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Energy piles have recently emerged as a viable alternative to borehole heat exchangers, but their energy efficiency has so far seen little research. In this work, a finite element numerical model is developed for the accurate 3D analysis of transient diffusive and convective heat exchange phenomena taking place in geothermal structures. The model is validated by reproducing both the outcome of a thermal response test carried out on a test pile, and the average response of the linear heat source analytical solution. Then, the model is employed to carry out a parametric analysis to identify the key factors in maximising the pile energy efficiency. It is shown that the most influential design parameter is the number of pipes, which can be more conveniently increased, within a reasonable range, compared to increasing the pile dimensions. The influence of changing pile length, concrete conductivity, pile diameter and concrete cover are also discussed in light of their energetic implications. Counter to engineering intuition, the fluid flow rate does not emerge as important in energy efficiency, provided it is sufficient to ensure turbulent flow. The model presented in this paper can be easily adapted to the detailed study of other types of geothermal structures.

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Section: Theoretical Backgroundmentioning

confidence: 99%

Influences on the thermal efficiency of energy piles

Cecinato

Loveridge

2015

Energy

128

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“…However, coarse blocks are usually only connected at single points, thereby limiting heat transfer in between them. Thermal radiation (iii) is subdivided into shortwave radiation originating from the sun, and longwave radiation from heated-up rock material, the sky and potentially from adjacent terrain (Fillion et al 2011;Scherler et al 2014;Aubry-Wake et al 2018). Shortwave radiation influencing the blocky surface layer and its potential snow-cover is further affected by aspect, slope and other shading effects.…”

Section: Introductionmentioning

confidence: 99%

Controlling factors of microclimate in blocky surface layers of two nearby relict rock glaciers (Niedere Tauern Range, Austria)

Wagner

Pauritsch

Mayaud

et al. 2019

Geografiska Annaler: Series A, Physical Geography

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Coarse blocky material is known to have a ground cooling effect compared to other types of unconsolidated surface material, which may have an influence on spatial distribution and conservation of permafrost. In the light of climate warming, this effect may retard permafrost degradation or exert prolonged ground cooling in general. To contribute to a better understanding of this ground cooling effect and potential influencing factors, the thermal regime of blocky surface layers of two comparable nearby relict rock glaciers with opposing aspects was investigated. Air, surface and shallow ground temperature at 1 m depth were continuously measured over a four-year period at nine locations distributed over two rock glaciers. The blocky surface layer of the SWexposed rock glacier exhibits lower and more heterogeneous temperatures than the NE-oriented despite a higher potential solar radiation. The data suggest a thinner or more discontinuous seasonal snow cover at the SW-exposed rock glacier, causing a more efficient winter cooling. The importance of air flow driven heat transfer as a source of cooling is supported by the data. Results illustrate thermal heterogeneities within blocky layers and the importance of the seasonal snow cover pattern in addition to topography and microclimatic variability in high relief terrain is hypothesized.

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“…In the measured energy balance the use of additional terms for radiative heat transfer between the blocks (see, e.g., Kunii and Smith, 1960;Fillion et al, 2011), heat storage change and turbulent heat flux in the blocky surface layer allowed for the approximation of seasonal freezing and thawing processes within the active layer and the permafrost.…”

Section: Introductionmentioning

confidence: 99%

A two-sided approach to estimate heat transfer processes within the active layer of the Murtèl–Corvatsch rock glacier

et al. 2014

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Abstract. The thermal regime of permafrost on scree slopes and rock glaciers is characterized by the importance of air flow driven convective and advective heat transfer processes. These processes are supposed to be part of the energy balance in the active layer of rock glaciers leading to lower subsurface temperatures than would be expected at the lower limit of discontinuous high mountain permafrost. In this study, new parametrizations were introduced in a numerical soil model (the Coup Model) to simulate permafrost temperatures observed in a borehole at the Murtèl rock glacier in the Swiss Alps in the period from 1997 to 2008. A soil heat sink and source layer was implemented within the active layer, which was parametrized experimentally to account for and quantify the contribution of air flow driven heat transfer on the measured permafrost temperatures. The experimental model calibration process yielded a value of about 28.9 Wm −2 for the heat sink during the period from mid September to mid January and one of 26 Wm −2 for the heat source in the period from June to mid September. Energy balance measurements, integrated over a 3.5 m-thick blocky surface layer, showed seasonal deviations between a zero energy balance and the calculated sum of the energy balance components of around 5.5 Wm −2 in fall/winter, −0.9 Wm −2 in winter/spring and around −9.4 Wm −2 in summer. The calculations integrate heat exchange processes including thermal radiation between adjacent blocks, turbulent heat flux and energy storage change in the blocky surface layer. Finally, it is hypothesized that these deviations approximately equal unmeasured freezing and thawing processes within the blocky surface layer.

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Thermal radiation and conduction properties of materials ranging from sand to rock-fill

Cited by 32 publications

References 28 publications

Influences on the thermal efficiency of energy piles

Influences on the thermal efficiency of energy piles

Controlling factors of microclimate in blocky surface layers of two nearby relict rock glaciers (Niedere Tauern Range, Austria)

A two-sided approach to estimate heat transfer processes within the active layer of the Murtèl–Corvatsch rock glacier

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