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Abstract  

Changes in the thermal conductivities of paraffin and mono ethylene glycol (MEG) as a function of β-SiC nanoparticle concentration and size was studied. An enhancement in the effective thermal conductivity was found for both fluids (i.e., both paraffin and MEG) upon the addition of nanoparticles. Although an enhancement in thermal conductivity was found, the degree of enhancement depended on the nanoparticle concentration in a complex way. An increase in particle-to-particle interactions is thought to be the cause of the enhancement. However, the enhancement became muted at higher particle concentrations compared to lower ones. This phenomenon can be related to nanoparticles interactions. An improvement in the thermal conductivities for both fluids was also found as the nanoparticle size shrank. It is believed that the larger Brownian motion for smaller particles causes more particle-to-particle interactions, which, in turn, improves the thermal conductivity. The role that the base-fluid plays in the enhancement is complex. Lower fluid viscosities are believed to contribute to greater enhancement, but a second effect, the interaction of the fluid with the nanoparticle surface, can be even more important. Nanoparticle-liquid suspensions generate a shell of organized liquid molecules on the particle surface. These organized molecules more efficiently transmit energy, via phonons, to the bulk of the fluid. The efficient energy transmission results in enhanced thermal conductivity. The experimentally measured thermal conductivities of the suspensions were compared to a variety of models. None of the models proved to adequately predict the thermal conductivities of the nanoparticle suspensions.

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that have a small diameter measured in nanoscale in various base fluids took high interest as an enhancement technique called nanofluid [ 6 ]-[ 8 ]. The effect of using this technique was examined experimentally and numerically using various

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ways that have taken a broad interest in recent years is the use of nanofluid that is clearly shown by an increase in the number of articles in this field [ 6 ]. This method is based on improving the thermal properties of the base fluid by adding small

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non-metallic nanoparticles in the various base fluids to produce “nanofluid”. All categories aimed to improve heat transfer and decrease heat losses by minimizing the thermal boundary condition and increasing the turbulent flow of the fluid flow, which

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Abstract  

The increasing application of biobased lubricants could significantly reduce environmental pollution and contribute to the replacement of petroleum base oils. Vegetable oils are recognized as rapidly biodegradable and are thus promising candidates for use as base fluids in formulation of environment friendly lubricants. Although many vegetable oils have excellent lubricity, they often have poor oxidation and low temperature stability. Here in, we report the lubricant potential of Moringa oil, which has 74% oleic acid content and thus possess improved oxidation stability over many other natural oils. For comparison, Jatropha oil, cottonseed oil, canola oil and sunflower oil were also studied. Among these oils, Moringa oil exhibits the highest thermo-oxidative stability measured using PDSC and TG. Canola oil demonstrated superior low temperature stability as measured using cryogenic DSC, pour point and cloud point measurements. The friction and wear properties were measured using HFRR. Overall, it was concluded that Moringa oil has potential in formulation of industrial fluids for high temperature applications.

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In the present study, fully developed laminar flow with forced convection heat transfer of Al2O3/water and TiO2/water nanofluids inside a vertical tube subjected by constant heat flux from the wall was numerically analyzed using Ansys Fluent release 17.2. In this work, the single-phase model was proposed to simulate the water and nanofluids heat transfer characteristics; spherical nanoparticles with a constant diameter equal to 30 nm are used. The study has been carried out on a Reynolds number with ranges (400-2000) and nanoparticles volume concentration up to 1.5%. the results show that the average Nusselt number for nanofluid is higher than that the base fluid (water) especially for TiO2/water nanofluid, the Nusselt number increased with increasing Reynolds number and volume concentration in all cases. The enhancement ratio for nanofluids compared to water at different volume friction was studied; the higher improvement is about 3.51% for TiO2/water nanofluid with 1.5% volume fraction. Moreover, a study for pressure drop along vertical tube was discussed.

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Formulation of grease is shown in Table 2 . The grease consists of synthetic and mineral oils as a base fluid, Lithium stearate (LiST), Lithium 12-hydroxystearate (LiOHST), and silica (SiO 2 ) as a thickener and polymer (PTFE) additive A (A1-5%, A2

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Journal of Thermal Analysis and Calorimetry
Authors: Benigno Barbés, Ricardo Páramo, Francisco Sobrón, Eduardo Blanco, and Carlos Casanova

the most characteristic properties of a nanofluid is a substantial increase in thermal conductivity and a stronger temperature-dependent thermal conductivity than in the base fluid alone. Extensive experimental research is required into the thermal

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[ 29 ]. If the timely release of heat could not be realized, the freezing process will be hindered. After adding the nanoparticles to the base fluid, the fluid has higher thermal conductivity than before. Therefore, the freezing rate of PCMs is

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conductivity better than the thermal conductivity of base fluids [ 6 ]-[ 11 ]. Numerous investigators have been studied the pool boiling of nanofluids with different operating conditions to understand the mechanism thoroughly. Yang and Maa [ 12 ] conducted

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