Isochoric thermal conductivity of solid <i>n</i>-alkanes: Hexane C6H14

Konstantinov, V. A.; Revyakin, V. P.; Sagan, V. V.

doi:10.1063/1.3604519

Cited by 9 publications

(6 citation statements)

References 15 publications

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“…Thermal conductivity experimental data are scarce in the literature, even for the solid and liquid phases of n -alkanes. Most works address n -alkanes with carbon numbers <20. − The works of Vélez and co-workers , present data of n -alkanes thermal conductivities, in the liquid and solid phases, in good agreement with results from other studies. ,, These works suggested that n -alkanes have their thermal conductivity enhanced by a factor of 2–3 when passing from the liquid to the solid phase.…”

Section: Introductionsupporting

confidence: 57%

Wax Deposit Thermal Conductivity Measurements under Flowing Conditions

2017

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Thermal conductivities of wax deposits formed on the cooled wall of a channel were measured under flowing conditions, for different values of the Reynolds number (Re) in laminar flow. To this end, a laboratory-scale experiment was especially designed, employing a rectangular channel flow loop. The thermal conductivities were directly measured for steadystate conditions in deposits formed after 7 h of deposition. The cooled wall on which the deposits were formed was equipped with embedded heat flux and thermocouple sensors. A micrometer-driven temperature probe of small dimensions was installed at the opposite channel wall and could be traversed across the channel, yielding the temperature profile of the deposited wax layer, as well as the liquid/deposit interface temperature. Deposit compositions were obtained by high-temperature gas chromatography. Thickness-averaged deposit thermal conductivities were obtained from the deposit thickness, heat flux, and interface-to-wall temperature measurements. The thermal conductivity results obtained for these well consolidate deposits did not display any sensitivity to the Re values tested, although the deposit wax content was seen to increase with Re. This finding was related to the nonhomogeneous character of the thick deposits studied. Temperature profiles within the wax deposit measured with the traversing temperature probe revealed small deviations from the linear profile expected for a one-dimensional, steadystate solution, considering a constant value for the thermal conductivity across an homogeneous deposit. These deviations were attributed to transverse variations of the deposit thermal conductivity. Local values of the thermal conductivity across the deposit were measured, revealing higher values closer to the deposit/liquid interface region, compared to those observed in the near-wall region. This variation was associated with the higher liquid fraction present in the deposit near the cold wall. The sensitive of the deposit thermal conductivity to the deposit liquid fraction was used as the basis for a novel technique developed to estimate the liquid and solid fraction distribution across the deposit. The technique was able to capture the increase in liquid fraction close to the cold wall, compared to the near-interface region, for the experimental conditions tested.

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Section: Introductionsupporting

confidence: 57%

Wax Deposit Thermal Conductivity Measurements under Flowing Conditions

2017

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“…The associated references are as follows. nCB ( 31 ); VO 2 ( 26 ); K, Zn, Cd, and Hg ( 32 ); c-Se ( 33 ); Ni-Mn-In alloy ( 13 ); C 6 H 14 ( 34 ); Sn, In, and LiNO 3 ( 15 ); C/C 16 H 34 composite ( 17 ); Ge 2 Sb 2 Te 5 ( 27 ); azobenzene polymers ( 14 ). ( D ) Multiple on/off thermal cycles of nanofiber #2 around the phase transition temperature of 440 K.…”

Section: Resultsmentioning

confidence: 99%

High-contrast and reversible polymer thermal regulator by structural phase transition

et al. 2019

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In comparison with the advancement of switchable, nonlinear, and active components in electronics, solid-state thermal components for actively controlling heat flow have been extremely rare. We demonstrate a high-contrast and reversible polymer thermal regulator based on the structural phase transition in crystalline polyethylene nanofibers. This structural phase transition represents a dramatic change in morphology from a highly ordered all-trans conformation to a combined trans and gauche conformation with rotational disorder, leading to an abrupt change in phonon transport along the molecular chains. For five nanofiber samples measured here, we observe an average thermal switching ratio of ~8× and maximum switching ratio of ~10×, which occurs in a narrow temperature range of 10 K across the structural phase transition. To the best of our knowledge, the ~10× switching ratio exceeds any reported experimental values for solid-solid and solid-liquid phase transitions of materials. There is no thermal hysteresis observed upon heating/cooling cycles.

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“…The thermal conductivity of Cu wire is affected by magnetic field, with experiment at 4.2 K recording thermal conductivity decrease and in proportionality under such fields (and Pure/Compound (H 2 O [35], c-Se [36], C 6 H 14 [37,38], NaF [39]) Passive Low Dimensionality…”

Section: Thermal Conductivity Switches (Tcs)mentioning

confidence: 99%

Thermal conductivity switch: Optimal semiconductor/metal melting transition

Kim

Kaviany

2016

Phys. Rev. B

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Scrutinizing distinct solid/liquid (s/l) and solid/solid (s/s) phase transitions (passive transitions) for large change in bulk (and homogenous) thermal conductivity, we find the s/l semiconductor/metal (S/M) transition produces largest dimensionless thermal conductivity switch (TCS) figure of merit Z TCS (change in thermal conductivity divided by smaller conductivity). At melting temperature, the solid phonon and liquid molecular thermal conductivities are comparable and generally small, so the TCS requires localized electron solid and delocalized electron liquid states.For cyclic phase reversibility, the congruent phase transition (no change in composition) is as important as the thermal transport. We identify XSb and XAs (X = Al, Cd, Ga, In, Zn) and describe atomic-structural metrics for large Z TCS , then show the superiority of S/M phonon-to electrondominated transport melting transition. We use existing experimental results and theoretical and ab initio calculations of the related properties for both phases (including the Kubo-Greenwood and Bridgman formulations of liquid conductivities). The 5p orbital of Sb contributes to the semiconductor behavior in the solid-phase bandgap and upon disorder and bond-length changes in the liquid phase this changes to metallic, creating the large contrast in thermal conductivity.The charge density distribution, electronic localization function, and electron density of states are used to mark this S/M transition. For optimal TCS, we examine the elemental selection from the transition-, basic-and semimetals and semiconductor groups. For CdSb, addition of residual Ag suppresses the bipolar conductivity and its Z TCS is over 7, and for Zn 3 Sb 2 it is expected to be over 14, based on the structure and transport properties of the better known β-Zn 4 Sb 3 . This is the highest Z TCS identified. In addition to the metallic melting, the high Z TCS is due to the electron-poor nature of II-V semiconductors leading to the significantly low phonon conductivity.

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Isochoric thermal conductivity of solid n-alkanes: Hexane C6H14

Cited by 9 publications

References 15 publications

Wax Deposit Thermal Conductivity Measurements under Flowing Conditions

Wax Deposit Thermal Conductivity Measurements under Flowing Conditions

High-contrast and reversible polymer thermal regulator by structural phase transition

Thermal conductivity switch: Optimal semiconductor/metal melting transition

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