Simplified Transient Hot-Wire Method for Effective Thermal Conductivity Measurement in Geo Materials: Microstructure and Saturation Effect

Merckx, Benoit; Dudoignon, P.; Garnier, J. P.; Marchand, D.

doi:10.1155/2012/625395

Cited by 27 publications

(17 citation statements)

References 31 publications

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“…For a good measurement, the long metallic wire is immersed in an homogeneous medium with uniform initial temperature, heated with a constant heat flux per unit length, and then the temperature rise T(t) of the wire is measured. The working equation is based on a specific solution to Fourier's law and can be found in standard texts (Merckx, Dudoignon, Garnier, & Marchand, 2012). Before measuring the thermal conductivity, the device was calibrated with glycerin.…”

Section: Thermal Conductivity Measurementsmentioning

confidence: 99%

Stability and thermal conductivity of water-based carbon nanotube nanofluids

2015

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Section: Thermal Conductivity Measurementsmentioning

confidence: 99%

Stability and thermal conductivity of water-based carbon nanotube nanofluids

2015

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“…Following principles similar to those of the needle-probe method, multi-needle probes have been developed, which enable the measurement of different soil properties within the same soil volumes [52][53][54][55].…”

Section: Needle-probe Methodsmentioning

confidence: 99%

Characterisation of Ground Thermal and Thermo-Mechanical Behaviour for Shallow Geothermal Energy Applications

et al. 2017

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Increasing use of the ground as a thermal reservoir is expected in the near future. Shallow geothermal energy (SGE) systems have proved to be sustainable alternative solutions for buildings and infrastructure conditioning in many areas across the globe in the past decades. Recently novel solutions, including energy geostructures, where SGE systems are coupled with foundation heat exchangers, have also been developed. The performance of these systems is dependent on a series of factors, among which the thermal properties of the soil play a major role. The purpose of this paper is to present, in an integrated manner, the main methods and procedures to assess ground thermal properties for SGE systems and to carry out a critical review of the methods. In particular, laboratory testing through either steady-state or transient methods are discussed and a new synthesis comparing results for different techniques is presented. In situ testing including all variations of the thermal response test is presented in detail, including a first comparison between new and traditional approaches. The issue of different scales between laboratory and in situ measurements is then analysed in detail. Finally, the thermo-hydro-mechanical behaviour of soil is introduced and discussed. These coupled processes are important for confirming the structural integrity of energy geostructures, but routine methods for parameter determination are still lacking.

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“…A hot wire method was used to measure thermal conductivity, which is illustrated in Fig. 2(a) [29][30][31] . A Nichrome wire was installed through the middle of a cylindrical Dragon skin structure.…”

Section: Soft Materials Characterizationmentioning

confidence: 99%

Liquid vaporization actuated soft structures with active cooling and heat loss control

Lee¹,

Loh²

2021

Smart Mater. Struct.

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Soft robotic systems that are inspired by nature utilize soft materials to perform various tasks in diverse environments. One promising method to control their movement is by utilizing liquid vaporization. In most cases, liquid with high vapor pressure is injected into hollow cavities inside the elastomer. Heating the system vaporizes the liquid, and the structure is inflated by the generated gas. However, there is a significant time lag between powering the system and structural actuation due to the slow increase in temperature that is exacerbated by heat loss. Simply using materials with low thermal conductivity can improve actuation, but the reduced heat loss concurrently increases cooling time during the reversing process. Furthermore, underwater actuation through vaporization remains a challenge, since heat loss becomes even more significant. To address these issues, this study aims to develop a system that can actively control heat loss to enhance both actuation and cooling while performing consistently even in extreme environments. First, double-walled structures were fabricated with silicone elastomer to drastically lower thermal conductivity. Next, a thermoelectric device was installed on the bottom layer to heat and cool the sealed liquid by reversing current flow. The low thermal conductivity of the double-walled structure enhanced actuation performance, while actively cooling the system with the thermoelectric device accelerated the reversing process. Structures with single-and double-layered walls were tested underwater to validate their performance. Finite element models verified the effects of wall designs on heat transfer and structural mechanics. Demonstration of enhanced reversible actuation of the system was performed using a soft anemone-like structure operated underwater.

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Simplified Transient Hot-Wire Method for Effective Thermal Conductivity Measurement in Geo Materials: Microstructure and Saturation Effect

Cited by 27 publications

References 31 publications

Stability and thermal conductivity of water-based carbon nanotube nanofluids

Stability and thermal conductivity of water-based carbon nanotube nanofluids

Characterisation of Ground Thermal and Thermo-Mechanical Behaviour for Shallow Geothermal Energy Applications

Liquid vaporization actuated soft structures with active cooling and heat loss control

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