Experimental Investigation Of Thermophysical Properties Research Articles

Experimental investigation of thermophysical properties of Al2O3–water nanofluid: Role of surfactants

Nanofluids are colloidal suspension of nanoparticles that have attracted much attention due to their enhanced heat transfer characteristics. Stability of the nanofluid is important for industrial applications. Although several researchers studied thermophysical properties of nanofluids, the literature is replete with contradictory results. The aim of the present work is to experimentally investigate the stability and properties of Al2O3-water nanofluid and the effect of surfactant on those; the effects of both temperature (20–60°C) and solid volume fractions (0.1–2.0%) of nanofluids are also analyzed. Stability of the nanoparticle suspensions is investigated with different surfactants, when sodium dodecylbenzenesulfonate (SDBS) is found to offer the best stabilization. TEM images show presence of rod-like particle of 20–70nm size. DLS measurements indicate that the presence of SDBS surfactant reduces particle clustering and polydispersity index of the suspension. Rheological measurements show that viscosity of Al2O3-water based nanofluids increases with solid volume fraction (φ=0.1–1.0%) and decreases with temperature, while the thermal conductivity increases with the increase of both solid volume fraction (0.1–2.0%) and temperature. The observed values of thermal conductivity and viscosity are compared with different established models. Finally, a sensitivity analysis is performed, which reveals that, for a given temperature, the sensitivity of thermal conductivity increases with the particle loading. The results provide comprehensive thermophysical property database of water-based Al2O3 nanofluids for different engineering applications.

Experimental investigation of thermophysical properties of eutectic Mo–C, graphite and tantalum at high temperatures

An experimental technique based on fast electrical heating for investigation of thermophysical properties of refractory materials under high pressures and at high temperatures is considered. A set of thermophysical properties of refractory materials such as specific enthalpy, specific heat capacity, specific resistivity, melting heat of eutectic Mo-C and thermal expansion of graphite and tantalum were determined. The obtained temperature of eutectic melting of MoC0.82 shows close agreement with equilibrium Mo-C phase diagram.

Experimental investigation of thermophysical properties and heat transfer rate of covalently functionalized MWCNT in an annular heat exchanger

In a novel direct amidation, multi-walled carbon nanotubes (MWCNT) is covalently functionalized with aspartic acid (Asp) to achieve a highly dispersed colloidal suspension including MWCNT. After investigation of colloidal stability of functionalized MWCNT with Asp (MWCNT-Asp) in aqueous media by UV–Vis spectroscopy, less than 20% sediment was occurred for highest weight concentration of 0.1%. The prepared coolants had some promising properties such as high thermal conductivity as compared with base fluid. Also, thermophyisical properties were investigated to check its suitability. The prepared water-based coolants with different weight fractions of MWCNT-Asp were experimentally investigated in terms of heat transfer rate in a horizontal annular heat exchanger. Forced convection heat transfer coefficient and pressure drop were investigated in transition and turbulent regimes for three different heat fluxes and four weight fractions. Annular heat exchanger showed a significant increase in heat transfer rate. Also poor change in the pressure drop in the presence of different weight concentrations provides a suitable condition for this novel alternative coolant. Also, insignificant increase in pumping power was obtained, which shows its suitability for industrial applications.

Experimental investigation of thermophysical properties, entropy generation and convective heat transfer for a nitrogen-doped graphene nanofluid in a laminar flow regime

Nitrogen-doped graphene (NDG) nanofluids are prepared using a two-step method in an aqueous solution of 0.025wt% Triton X-100 as a surfactant with various nanosheets at several concentrations (0.01, 0.02, 0.04, 0.06wt%). The results are reported of experiments on the thermal conductivity, viscosity and convective heat transfer behavior of NDG nanofluids undergoing laminar flowing in a circular tube. The results indicate that, compared to the base liquid, the thermal conductivity is enhanced for NDG nanofluids by between 22.15% and 36.78%, and the heat transfer coefficient of the NDG nanofluids is increased by 7–50%. The measurements also show that the pressure drop of the nanofluids increased by between 0.08% and 14.4%. In addition, the overall performance of the tested nanofluids are assessed based on the performance index and optimum work conditions, demonstrating that the nanofluids can be advantageous in practical applications.

Experimental investigation of thermo-physical properties, convective heat transfer and pressure drop of functionalized graphene nanoplatelets aqueous nanofluid in a square heated pipe

In the present study, a facile method is used for preparation of functionalized graphene nanoplatelets (f-GNP) nanofluids. The effective thermal conductivity, density, viscosity, specific heat capacity, overall heat transfer coefficient and friction factor for fully developed turbulent flow of f-GNP/water nanofluids flowing through a square pipe at a constant heat flux were studied. f-GNP uniform nanocomposite was produced from a simple acid treatment reaction procedure. The surface characterization was performed by various techniques such as XRD, FESEM, FTIR and Raman. The f-GNP nanofluids were prepared by dispersing the functionalized nanoparticles in base fluid (water) without the assistance of a surfactant. As made nanofluids were stable for a long time and no sedimentation was observed. The experimental data for f-GNP nanofluids have shown significant enhancement in thermal conductivity and overall heat transfer coefficient in comparison to the corresponding water data. The percentage of enhancement is a function of weight concentration of nanoparticles and temperature. Highest improvement of overall heat transfer coefficient is 19.68% with 9.22% raise in friction factor for the weight concentration of 0.1% at a Reynolds number of 17,500 compared to those data from the base fluid.

Temperature-dependent thermal conductivity of silicone-Al2O3 nanocomposites

This paper presents an experimental investigation of thermophysical properties of elastomeric nano-composites. Spherical alumina nanoparticles with a diameter of 150 nm were added to polydimethylsiloxane (PDMS), and batches of nanocomposites with different volume concentrations (up to 5 %) were produced. The thermal conductivity of the samples was acquired through the guarded heat flow meter method at nine temperature setpoints, ranging from 0 to 80 °C, and density measurements were carried out, in order to evaluate the composition of the samples. The results showed a significant increase in the thermal conductivity of PDMS with small additions of alumina nanoparticles. In addition, a notable linear decrease in conductivity was observed with increasing temperature. Finally, classical models were fitted to the experimental data and a discussion about the physical meaning of the adjusted parameters was carried out.

Experimental investigation of thermo-physical properties of platelet mesoporous SBA-15 silica particles dispersed in ethylene glycol and water mixture

This paper presents an experimental investigation of thermophysical properties of platelet mesoporous SBA-15 particles dispersed in 60:40 (v/v) ethylene glycol:water mixture. The effect of weight fraction of particles and temperature is studied on density, viscosity and thermal conductivity of nanofluids. The maximum measured thermal conductivity enhancement reaches up to 22% for the nanofluids containing 5 wt% of SBA-15 at 60 °C. The SBA-15 nanofluids show Newtonian behavior in the tested temperature range. Also, the relative density increases between 0.4% and 2.2% when the weight percent of the nanoparticles varies between 1 and 5 at 60 °C. Structural and morphological characterization of synthesized SBA-15 have been carried out using Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and N 2 adsorption–desorption isotherms methods.

An experimental investigation of thermo-physical properties and heat transfer performance of Al2O3-Aviation Turbine Fuel nanofluids

Aviation Turbine Fuel (ATF)-Al2O3 nanofluids are investigated for better heat transfer performance in a potential application of regeneratively cooled semi-cryogenic rocket engine thrust chambers. The volume concentration of Al2O3 nanoparticles is varied between 0 and 1%. To ensure a realistic evaluation, all properties of the nanofluids are experimentally measured rather than resorting to available formulae or empirical correlations. Among the thermo-physical properties, thermal conductivity and specific heat are measured separately using experimental set-ups fabricated in-house whereas the viscosity is determined using a commercial viscometer. The heat transfer coefficient is determined using a horizontal double tube counter-flow heat exchanger under turbulent flow conditions. At 1% particle volume concentration, the enhancement in the thermal conductivity is 40%, whereas the viscosity increases by 38%. The measured specific heats of the nanofluids do not exhibit appreciable difference within the range of the particle volume concentrations investigated. The heat transfer coefficient increases by 30% at 1% particle volume concentration and correspondingly leads to an enhancement of 10% in the Nusselt number. For the same value of pressure drop, the heat transfer performances of nanofluids are compared with those of ATF. The experimental results show that the maximum enhancement in the heat transfer coefficient observed for the same pressure drop is 28% and even the least enhancement obtained is 2%.

Variational Methods for Experimental Investigation of Thermophysical Properties and Thermal Analysis of Various Objects

The methods of automated determination of the thermophysical properties and thermal analysis of various objects (solid bodies,dispersed materials, and liquids) are substantiated. They are based on program variation of thermal fields in the experiment.

Experimental investigation of thermophysical properties of glass-fibre-resin materials from 10 to 400°K

Experimental investigation of thermophysical properties of glass-fibre-resin materials from 10 to 400°K

Experimental investigation of thermophysical properties of glass-fibre-resin materials from 10 to 400°K

Experimental installation for investigation of thermal conductivity, thermal diffusivity and heat capacity of constructional glass-fibre materials is described in short for the temperature range from 10 to 400°K. Thermal properties of the materials have been investigated in two directions, with a heat flux along and across the filling fibres. The results of investigation of multiple (1-, 5-, 10-, 60- and 100-fold) cooling effects on thermophysical properties of constructional glass-fibre materials are presented.