Assessment on the thermal and moisture migration of sand-based materials coupled with kaolin additive

Liang, Bin; Chen, Meiqian; Guan, Junli

doi:10.1007/s10973-022-11372-x

“…The addition of bentonite promotes the water holding capacity, mechanical and thermophysical properties of sand and y ash. Therefore, previous researchers reported that a mixture of bentonite/clay-based back ll material for various similar geothermal structures such as ground air heat exchanger (GAHE), high-level nuclear waste repository (HLWR) and ground source heat pump (GSHP) might be promising buffer and back ll material; due to its better performance over pure bentonite/clay with respect to heat storage-releasing abilities, swelling, water retention and mechanical properties [22][23][24][25]. Wang et al [22] reported that mixture of sand and bentonite as back ll materials of borehole heat exchangers and observed that wet thermal conductivity of bentonitesand showed higher value than normal sand-clay mixtures and found that the thermal conductivity increased 36.1%-26.7% by adding 10%-12% ne-coarse sand to bentonite.…”

Section: Introductionmentioning

confidence: 99%

“…Xu et al [24] reported addition of sand to the bentonite increase the thermal conductivity of the mixture and sand content below 38% and 39% should also su cient to achieve the swelling pressure above 1.0 MPa and the hydraulic conductivity lower than 10 − 12 m/s respectively. Liang et al [25] studied the thermal and moisture diffusion properties of sand-kaolin mixture for the application of GSHP and observed that the thermal conductivity of sand-kaolin is 2.81 Wm − 1 K − 1 with 10% water content, which is better than pure sand of thermal conductivity 1.81 Wm − 1 K − 1 . Cho et al [26,27] have studied the thermal conductivity of bentonite-sand mixes and found that the addition of sand with bentonite increases the thermal conductivity of mixtures at different γ d and w. Yu et al [28] have examined thermal conductivity of sand-kaolin mixture at varying clay contents, γ d and w and, the results con rm that thermal conductivity of the mixture increases with an increase of γ d , w, quartz content (q) and sand content (f s ).…”

Section: Introductionmentioning

confidence: 99%

Thermophysical Properties of Bentonite–Sand/Fly Ash-Based Backfill Materials for Underground Power Cable

Sah

¹

,

Kumar

²

,

Sreedeep

³

2023

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The surrounding (back ll) materials around the underground power cable systems are essential for dissipiating the heat away from it, during the exertion phases. The heat dissipiation restrains the thermal instability and risk of progressive drying of the back ll materials, thus, reduce thermal stress on power cable. Thermal instability is the reduction of thermal properties (conductivity or diffusivity) due to migration of moisture because of heat accumulation. Thus, the back ll materials should have adequate thermal properties and favorable water retention capacity, which will falicitate the heat transfer easily from the heat source to the surrounding area with minimal moisture migration. The bentonite have high water retention capacity, but low thermal conductivity. Sand/ y ash exhibit low water retention and have higher thermal conductivity than bentonite. The addition of bentonite promote the water holding capacity and thermo-physical properties of sand and y ash. Therefore, this study presents the thermal properties of back ll materials, bentonite-y ash (B-F) and bentonite-sand (B-S) at varying weigth-percent of sand and y ash with bentonite. various compositions of the mixtures were compacted to varying dry densities and water contents and thermal properties variation of back ll materials were measured using a dual thermal needle probe 'KD2 Pro 2008' at room temperature. The study deals with systematic evaluation of the volumetric speci c heat capacity, thermal conductivity and diffusivity of back ll materials against varying dry density and water content. The threshold water content (TWC) has been determined from the thermal diffusivity-water content variation curve and it has correlated with plastic limit (PL) and optimum mosite conetn (OMC). Thereafter, the e cacy two thermal conductivity prediction models also were statistically evaluated with respect to experimental results.

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“…Xu et al [24] reported addition of sand to the bentonite increase the thermal conductivity of the mixture and sand content below 38% and 39% should also su cient to achieve the swelling pressure above 1.0 MPa and the hydraulic conductivity lower than 10 − 12 m/s respectively. Liang et al [25] studied the thermal and moisture diffusion properties of sand-kaolin mixture for the application of GSHP and observed that the thermal conductivity of sand-kaolin is 2.81 Wm − 1 K − 1 with 10% water content, which is better than pure sand of thermal conductivity 1.81 Wm − 1 K − 1 . Cho et al [26,27] have studied the thermal conductivity of bentonite-sand mixes and found that the addition of sand with bentonite increases the thermal conductivity of mixtures at different γ d and w. Yu et al [28] have examined thermal conductivity of sand-kaolin mixture at varying clay contents, γ d and w and, the results con rm that thermal conductivity of the mixture increases with an increase of γ d , w, quartz content (q) and sand content (f s ).…”

Section: Introductionmentioning

confidence: 99%

“…The addition of bentonite promotes the water holding capacity, mechanical and thermophysical properties of sand and y ash. Therefore, previous researchers reported that a mixture of bentonite/clay-based back ll material for various similar geothermal structures such as ground air heat exchanger (GAHE), high-level nuclear waste repository (HLWR) and ground source heat pump (GSHP) might be promising buffer and back ll material; due to its better performance over pure bentonite/clay with respect to heat storage-releasing abilities, swelling, water retention and mechanical properties [22][23][24][25]. Wang et al [22] reported that mixture of sand and bentonite as back ll materials of borehole heat exchangers and observed that wet thermal conductivity of bentonitesand showed higher value than normal sand-clay mixtures and found that the thermal conductivity increased 36.1%-26.7% by adding 10%-12% ne-coarse sand to bentonite.…”

Section: Introductionmentioning

confidence: 99%

Thermophysical Properties of Bentonite-sand/fly ash Based Backfill Materials for Underground Power Cable

Sah

¹

,

Kumar

²

,

Sreedeep

³

2022

Preprint

0

View full text Add to dashboard Cite

The surrounding (backfill) materials around the underground power cable systems are essential for dissipiating the heat away from it, during the exertion phases. The heat dissipiation restrains the thermal instability and risk of progressive drying of the backfill materials, thus, reduce thermal stress on power cable. Thermal instability is the reduction of thermal properties (conductivity or diffusivity) due to migration of moisture because of heat accumulation. Thus, the backfill materials should have adequate thermal properties and favorable water retention capacity, which will falicitate the heat transfer easily from the heat source to the surrounding area with minimal moisture migration. The bentonite have high water retention capacity, but low thermal conductivity. Sand/fly ash exhibit low water retention and have higher thermal conductivity than bentonite. The addition of bentonite promote the water holding capacity and thermo-physical properties of sand and fly ash. Therefore, this study presents the thermal properties of backfill materials, bentonite-fly ash (B-F) and bentonite-sand (B-S) at varying weigth-percent of sand and fly ash with bentonite. various compositions of the mixtures were compacted to varying dry densities and water contents and thermal properties variation of backfill materials were measured using a dual thermal needle probe ‘KD2 Pro 2008’ at room temperature. The study deals with systematic evaluation of the volumetric specific heat capacity, thermal conductivity and diffusivity of backfill materials against varying dry density and water content. The threshold water content (TWC) has been determined from the thermal diffusivity-water content variation curve and it has correlated with plastic limit (PL) and optimum mosite conetn (OMC). Thereafter, the efficacy two thermal conductivity prediction models also were statistically evaluated with respect to experimental results.

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Theoretical calculation model for the thermal conductivity of scrap tire rubber–sand mixtures based on soil components

Wang

¹

,

Wu

²

,

Cai

³

et al. 2023

J Therm Anal Calorim

1

0

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Assessment on the thermal and moisture migration of sand-based materials coupled with kaolin additive

Cited by 6 publications

References 69 publications

Thermophysical Properties of Bentonite–Sand/Fly Ash-Based Backfill Materials for Underground Power Cable

Thermophysical Properties of Bentonite–Sand/Fly Ash-Based Backfill Materials for Underground Power Cable

Thermophysical Properties of Bentonite-sand/fly ash Based Backfill Materials for Underground Power Cable

Theoretical calculation model for the thermal conductivity of scrap tire rubber–sand mixtures based on soil components

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