Laboratory investigations of thermal properties of crushed rock materials

Rieksts, Karlis; Hoff, Inge; Kuznetsova, Ekaterina; Côté, Jean

doi:10.1201/9781315100333-19

Cited by 5 publications

(19 citation statements)

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“…Different numbers of convection cells within a given geometry will result in different Nu-Ra relationships [8]. However, as shown later, the same Nu-Ra relationship can be applied to other geometry and air convection cell conditions to yield reasonable intrinsic permeability values [6,27]. Figure 4 is a schematic of typical experimental results of natural downward (no air convection) and upward (with air convection) heat transfer tests on coarse open-graded materials.…”

Section: A Methods For Determining the Intrinsic Permeability From Natmentioning

confidence: 99%

Section: Experiments By Rieksts Et Al (2017)mentioning

confidence: 99%

“…The first phase included a test using pure sand for validation of conductive heat transfer. The second phase was the validation of convective heat transfer, the results of which are reported in Rieksts et al (2017) [27]. Figure 13 After the first two initial phases to validate the experimental setup, the study continued with tests using road construction materials.…”

Section: Experiments By Rieksts Et Al (2017)mentioning

confidence: 99%

“…A stronger line heat source was used for these experiments, which successfully initiated convection in a 2-dimensional pattern and remained stable throughout the test. [27,31]. Using Equation 11to establish K gives a best-fit value of 3.38 × 10 −6 m 2 .…”

Section: Reanalysis Of Johansen's (1975) Data By Côté Et Al (2011)mentioning

confidence: 99%

“…Experimental data on upward and downward heat flow through natural cobbles (Rieksts et al, 2017 [27]). Table 5 summarizes the material characteristics, experimental results and established K values of the tests reported by Rieksts et al (2017Rieksts et al ( , 2020 [27,31]. Using Equation (11) to establish K gives a best-fit value of 3.38 × 10 −6 m 2 .…”

Section: Reanalysis Of Johansen's (1975) Data By Côté Et Al (2011)mentioning

confidence: 99%

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Establishment of Intrinsic Permeability of Coarse Open-Graded Materials: Review and Analysis of Existing Data from Natural Air Convection Tests

et al. 2020

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This paper presents a review and analysis of large-scale air convection tests and the establishment of intrinsic permeability in coarse open-graded materials. Natural air convection can make a significant contribution to heat transfer during cooling periods. In seasonally freezing environments this can result in excessive frost penetration and subsequent frost-related problems. Intrinsic permeability largely defines the onset of convective heat transfer in granular materials. Conventional methods for measuring intrinsic permeability cannot be applied to very coarse materials. Large-scale laboratory experiments on natural air convection can serve as an alternative method for determining this crucial parameter. This paper gives an overview of four different experimental test setups for measuring natural air convection, all differing in physical shape, boundary conditions and heat flux/temperature measurement devices. Comparison between these is difficult because the air convection pattern can differ and in some cases the shape and number of convection cells cannot be validated. Most of the studies available in the literature use theoretical equations to approximate intrinsic permeability. A method based on the analytical Nu-Ra number relationship is employed to establish the values of intrinsic permeability. Tests that provide enough data to enable the use of the Nu-Ra relationship are very limited. The overall results show a reasonable correlation between experiment-based intrinsic permeability and theoretical approximation. However, several issues must be addressed: first, differences may exist between the intrinsic permeability of natural and of crushed materials due to the shape effect. Second, the method used is in theory valid only for two-dimensional air convection within a square enclosure heated from below. Yet the results show that this method could be extended to other conditions with a certain degree of confidence. Third, a good estimate of intrinsic permeability is possible only with accurate experimental measurement.

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Section: A Methods For Determining the Intrinsic Permeability From Natmentioning

confidence: 99%

Section: Experiments By Rieksts Et Al (2017)mentioning

confidence: 99%

Section: Experiments By Rieksts Et Al (2017)mentioning

confidence: 99%

Section: Reanalysis Of Johansen's (1975) Data By Côté Et Al (2011)mentioning

confidence: 99%

Section: Reanalysis Of Johansen's (1975) Data By Côté Et Al (2011)mentioning

confidence: 99%

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Establishment of Intrinsic Permeability of Coarse Open-Graded Materials: Review and Analysis of Existing Data from Natural Air Convection Tests

et al. 2020

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Natural factors related to the differential heating of aggregates exposed to microwaves

Trigos

Gallego

2022

Construction and Building Materials

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Experimental Study on the Effect of Soil Moisture Content on Critical Temperature Rise for Typical Cable Backfill Materials

Rieksts

Eberg

2023

IEEE Trans. Power Delivery

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The increased utilization of power grid requires operating power cables close to their thermal limit. Buried power cables in such condition experience thermal instability where thermal resistance increases as the moisture migrates away from the proximity of the cable forming a dry-out zone. While it is common to use a two-zone model to account for the dry-out zone in ampacity calculations, there is a limited number of studies on characterizing backfill materials for their critical temperature rise (Δθx), especially for crushed rock sands. In addition, dependency of the Δθx on moisture content is sometimes not acknowledged. This study measures the Δθx for three typical backfill materials and investigates the relationship between Δθx and moisture content. The results show that crushed rock sand has higher Δθx compared to natural sand. Overall, large range of Δθx was measured depending on moisture content and type of soil. Ampacity calculations with the established Δθx show that at low moisture content, the thermal resistivity of the soil has a higher influence on ampacity than Δθx. At relatively high moisture content, the Δθx becomes the predominant factor governing the overall ampacity.

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Laboratory investigations of thermal properties of crushed rock materials

Cited by 5 publications

References 1 publication

Establishment of Intrinsic Permeability of Coarse Open-Graded Materials: Review and Analysis of Existing Data from Natural Air Convection Tests

Establishment of Intrinsic Permeability of Coarse Open-Graded Materials: Review and Analysis of Existing Data from Natural Air Convection Tests

Natural factors related to the differential heating of aggregates exposed to microwaves

Experimental Study on the Effect of Soil Moisture Content on Critical Temperature Rise for Typical Cable Backfill Materials

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