Author(s): A. M. Shakya, V. K. R. Kodur
Abstract: This paper used the Hot Disk TPS to measure the thermal conductivity of several different spray applied fire resistive materials between a temperature of 20-1000°C. Mass loss and thermal strain were also investigated. These properties are crucial components of the material and decide how effectively it will perform in the face of a fire. Temperature was found to have a significant impact on the thermal conductivity, mass loss and thermal strain. These results enabled the authors to develop thermal property relationships which could be used in predictive modeling.
Author(s): Chi T. Do, Dale P. Bentz, Paul E. Stutzman
Abstract: Two calcium silicate boards of different densities, porosities and pore size were analyzed for their thermal properties, specifically thermal conductivity. The boards were heated from room temperature to 400°C and the thermal conductivity was monitored during this time. A separate experiment ‘aged’ the boards first by heating at 1000°C for 4 hours before testing the thermal conductivity from room temperature to 400°C once again. The experimental results were compared with three pre-existing theories that predict thermal conductivity of porous materials. These three theories are: Russell’s, Frey’s and Bruggeman’s. The theory of Russell and Frey agreed reasonably well with the experimentally determined (via Hot Disk) thermal conductivities, while the theory of Bruggeman did not agree well. ‘Aging’ the boards had a small but non-negligible effect on the thermal conductivity.
Investigation of Transmittance and Thermal Conductivity Properties of Silica Gels for Application as Transparent Heat Insulation Materials
Author(s): Christos G. Aneziris, Friederike Klenert, Jens Fruhstorfer
Abstract: In this article the effectiveness of silica aerogels as a transparent heat insulation material (TIM) is studied. They are a good candidate for this application as the amount of energy that they absorb and emit is adjustable. The effects of different treatments (hydrothermal and firing) on the thermal properties of the silica gels was studied, in addition to research on the most favorable conditions for use of this material as a TIM. Researchers wanted to optimize the thermal properties and transmittance values, as previous works had focused solely on one or the other. Thermal conductivity was measured using the TPS method. Results showed that hydrothermal treatment at 150°C with a 5 hour dwell time gave the lowest thermal conductivity, and this same treatment also provided the best combination with transmittance. The firing treatment was found to have no effect on the insulation properties.
Author(s): Ajay Kumar Tyagi, Ved Prakash, Vinay Kumar Tyagi
Abstract: Kerosene is used as a coolant in engines, however like many conventional heat transfer fluids, it has a low thermal conductivity. Nanofluids are suspensions of thermally conductive nanometer sized particles in a base fluid. This paper explores the thermal properties of a Kerosene based nanofluid with copper oxide (CuO) nanoparticles. The thermal conductivity meter (TPS-500) measured the thermal conductivity of copper oxide/Kerosene nanofluids using the transient plane source (TPS) technique. Nanofluid samples of 60 ml ranging from 0.01-0.08% concentration were measured for 20 seconds at 25mW. Results showed that the thermal conductivity of the CuO/Kerosene nanofluid increased with CuO concentration up to a certain point, then slightly declined.
Thermal Conductivity and Thermal Diffusivity Analyes of Low-Density Polyethylene Composites Reinforced with Sisal, Glass and intimately mixed Sisal/Glass Fibres
Author(s): C. Pavithran, G. Kalaprasad, G. Mathew, P. Pradeep, S. Thomas
Abstract: The thermal conductivity and thermal diffusivity of SRP (sisal-reinforced polyethylene), GRP (glass-reinforced polyethylene), and GSRP (sisal/glass hybrid fibre-reinforced polyethylene) were tested from 120 to 350K. Results showed variances in thermal conductivity values with varying temperatures in materials containing different orientations of sisal fibres. Due to the anisotropic nature of the SRP fibre, there is a difference in the thermal conductivity readings from the parallel to the perpendicular direction. The GRP fibre is isotropic in nature, and therefore the difference between the thermal conductivity values of each fibre direction is minimal. The thermal conductivity of glass fibres is enhanced, mostly in part due to the presence of iron ions. Researchers have also noted that due to the reduction in the mean free path of photons, the variation of thermal diffusivity with temperature is opposite to that of thermal conductivity.
Author(s): Patrick J. Shamberger, Timothy Reid
Abstract: Lithium nitrate trihydrate (LiNO3·3H2O) has many traits that are desirable for thermal energy storage (TES) materials. This study tests the thermophysical properties of LiNO3·3H2O between 253-353 K in comparison to effective TES materials: water and paraffin. A Hot Disk TPS 2500S measured the thermal conductivity of the solid LiNO3·3H2O samples using the transient plane source (TPS) method. Results showed that LiNO3·3H2O had a higher thermal conductivity than paraffin, giving it the potential to be a competitive TES material in the future.
Author(s): Andrea Gasparella, Giovanni Longo
Abstract: H2O/KCOOH (potassium formate) is a highly soluble hygroscopic salt solution that has the potential to be used as a desiccant. However, the thermophysical properties of H2O/KCOOH are only available for concentrations between 20-50%, which is not beneficial for their use as dehumidifiers. In this paper, a Transient Hot Disk TPS 2500S was used to measure the thermal conductivity of H2O/KCOOH solution with salt concentrations of 60-80% between 1 °C and 80 °C. The results of this experiment showed that H2O/KCOOH is sensitive to salt concentration, but resistant to temperature. Thermal conductivity increased with temperature, but decreased inversely to the salt concentration. Overall, the thermal conductivity of the desiccant was 23-33% lower than water at the same temperature. Knowing the thermophysical properties of H2O/KCOOH over expanded conditions improves the chances that it will be used as a desiccant in the future.
Author(s): Amanda M. Tomson, Jason M. Keith, Julia A. King, Michael G. Miller
Abstract: Two different types of polyacrylonitrile carbon fibers (Fortafil 243 and Panex 30) were added to thermoplastic matrix (Vectra A950RX Liquid Crystal Polymer) in order to generate carbon fiber/liquid-crystal polymer composites. The in plane and through-plane thermal conductivities of these composites were then evaluated and compared to values generated from a theoretical model, with good agreement. Panex 30 gave higher in-plane thermal conductivity than Fortafil 243 for all volume fractions studied.
Author(s): Dongsheng Zhu, Hua Li, Jinwei Gao, Nan Wang, Xianju Wang, Xin-Fang Li, Xinfang Li
Abstract: Nanofluids are relatively new materials that are composed of liquids containing solid nanoparticles ranging from 1-100 nm. This study examined the thermal conductivity of Al2O3 (aluminum oxide)-H2O nanofluids in water under multiple pH and sodium dodecylbenzenesulfonate (SDBS) conditions. A hot disk transient plane source (TPS) was used to measure the thermal conductivities of the samples. It was found that when the pH of the nanofluid reached approximately 8.0, the solution moved away from the point of zero change (PZC) and the thermal conductivity of the solution increased. The PZC is the pH value where the nanofluid particles aggregate; when this state is disturbed, the particles spread out and heat can more efficiently pass through the sites on their surfaces. It was also discovered that the nanofluid became stabilized at a higher concentration of SDBS than the concentration where thermal conductivity was optimized. Therefore, particle stability is compromised when thermal conductivity is highest.
Author(s): Javier Artemio Narvaez
Abstract: Three techniques were compared for the determination of thermal conductivity in poly-alpha-olefin (PAO)-based nanofluids. The three methods that were used were the transient hot wire, transient plane source, and laser flash techniques. The effects of temperature, nanoparticle concentration, and shape on the thermal conductivity were also examined, and these effects were compared to those predicted by a previously determined model. It was found that the transient hot wire technique was the most accurate method for measuring the thermal conductivity of nanofluids, increasing the concentration of nanoparticles increased the thermal conductivity of the nanofluids, and that the shape of the nanoparticles had a weak impact on the thermal conductivity. Temperature was not found to have any significant influence on the thermal conductivity of the nanofluids that were tested.
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