Thermal Conductivity and Thermal Diffusivity Measurements of Wood in the Three Anatomic Directions Using the Transient Hot-Bridge Method

Faouel, Jihene; Mzali, Foued; Jemni, Abdelmajid; Nasrallah, Sassi Ben

doi:10.1615/specialtopicsrevporousmedia.v3.i3.50

Cited by 20 publications

(10 citation statements)

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“…Faouel et al 42 measured the thermal conductivity and diffusivity of samples from temperate and tropical wood species, wet or dry. They found that the axial thermal properties were much larger than radial and tangential ones.…”

Section: Methodsmentioning

confidence: 99%

Thermal Bridging Through Branches of Snow-Covered Shrubs Cool Down Permafrost in Winter

Dominé

Fourteau

Picard

et al. 2021

Preprint

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Warming-induced shrub expansion on Arctic tundra (Arctic greening) is thought to warm up permafrost by several degrees, as shrubs trap blowing snow and increase snowpack thermal insulation, limiting permafrost winter cooling and facilitating its thaw. At Bylot Island, (Canadian high Arctic, 73°N) we monitored permafrost temperature at nearby unmanipulated herb tundra and shrub tundra sites and unexpectedly observed that low shrubs cool permafrost by 1.21°C over the November-February period. This is despite a snowpack twice as insulating in shrubs. Using heat transfer models and finite-element simulations, we show that this winter cooling is caused by thermal bridging through frozen shrub branches. This effect largely compensates the warming effect induced by the more insulating snow in shrubs. The cooling is partly canceled in spring when shrub branches under snow absorb solar radiation and accelerate permafrost warming. The overall effect is expected to depend on snow and shrub characteristics and terrain aspect. These significant perturbations of the permafrost thermal regime by shrub branches should be considered in projections of permafrost thawing, nutrient recycling and greenhouse gas emissions.

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Section: Methodsmentioning

confidence: 99%

Thermal Bridging Through Branches of Snow-Covered Shrubs Cool Down Permafrost in Winter

Dominé

Fourteau

Picard

et al. 2021

Preprint

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“…4). Although some measured results did not follow this trend, the majority of the tests did behave as stated in the relevant literature (Bootle 1983;Yapici et al 2011;Faouel et al 2012). Table 5 compares the test results of balsa's TC using the needle probe procedure from the two tests conducted on separate occasions (test 2 was conducted 12 days after test 1).…”

Section: Resultsmentioning

confidence: 84%

“…Moreover, the rate of heat flow in the axial direction is two and a half times greater than the rate through the radial and tangential directions. Faouel et al (2012) also highlighted that "the axial TC is largely higher than in other directions and tangential TC is slightly lower than the radial TC". Additionally, Glass and Zelinka (2010) claimed the TC of timber is also affected by structural irregularities (checks and knots) and fibril angles.…”

Section: Thermal Conductivity Of Woodmentioning

confidence: 99%

“…2.). Where the literature states the tangential direction has the lowest TC value (Faouel et al 2012), in order to prove this using the needle probe method the probe was inserted parallel to the radial direction to measure the geometric mean for the axial/tangential grain directions. The purpose of performing the needle probe procedure on balsa samples was to generate quick results to determine if balsa has good thermal performance.…”

Section: Test Executionmentioning

confidence: 99%

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Thermal Conductivity of Papua New Guinea Balsa Wood Measured using the Needle Probe Procedure

Kotlarewski¹,

Ozarska²,

Gusamo³

2014

BioResources

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A study was undertaken with the aim to determine thermal properties of balsa wood grown in plantations in Papua New Guinea. Thermal conductivity values were measured using the needle probe procedure according to ASTM D5334 (2008). The mean thermal conductivity results of balsa were in the range of 0.0381 W/mK to 0.0665 W/mK, similar to other materials currently used as insulators in the construction industry. A balsa sample with a density of 113 kg m 3 had the lowest thermal conductivity value, 0.0339 W/mK, across the tangential and radial wood grain directions. Balsa is exported from Papua New Guinea mostly as endgrain panels to international markets to optimise its strength properties in the axial direction for applications that are exposed to compressive forces. This study revealed that there is the opportunity for Papua New Guinea balsa processors to consider producing perpendicular-grain panels for insulation markets, as the mean thermal conductivity values in this direction can be as low as 0.0381 W/mK, which is much lower than the thermal conductivity of the current end-grain panels at 0.0665 W/mK. The finding creates a potential design opportunity for balsa processors to consider entering new commercial markets to promote Papua New Guinea-grown balsa.

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“…This technique has a robust design suitable for many industrial applications, giving that it doesn't require specific fluid enclosure and have easy experimental procedure. This method is based on the transient hot-bridge (THB) [18][19][20], which has previously shown its efficiency with the classical identification procedure based on slop calculation for determining thermal conductivity of solids. In this paper, the THB is adapted to liquids with a new identification procedure, based on the instantaneous slope versus time.…”

Section: Introductionmentioning

confidence: 99%

Thermal Conductivity Measurements of Liquids with Transient Hot-Bridge Method

Albouchi¹,

Mzali²,

Saadaoui³

et al. 2019

I2M

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In this paper an electro-thermal method is used for measuring the thermal conductivity of liquids. This technique is based on eight heat sensing resistors which are connected to form a Wheatstone bridge. Measurements performed on several liquids covering a wide range of thermal properties validate the method. The total standard uncertainty of the experimental results was estimated to be less than 3.8 %. Good agreement is found between the measured values of the thermal properties and previously reported values in literature. Moreover, measurements using this method are less time consuming than using the classical methods. This technique may find practical application for the thermal characterization of complex fluids even when applying external electric or magnetic fields.

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Thermal Conductivity and Thermal Diffusivity Measurements of Wood in the Three Anatomic Directions Using the Transient Hot-Bridge Method

Cited by 20 publications

References 0 publications

Thermal Bridging Through Branches of Snow-Covered Shrubs Cool Down Permafrost in Winter

Thermal Bridging Through Branches of Snow-Covered Shrubs Cool Down Permafrost in Winter

Thermal Conductivity of Papua New Guinea Balsa Wood Measured using the Needle Probe Procedure

Thermal Conductivity Measurements of Liquids with Transient Hot-Bridge Method

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