In this study, the thermal conductivity and viscosity of TiO 2 nanoparticles in deionized water were investigated up to a volume fraction of 3 % of particles. The nanofluid was prepared by dispersing TiO 2 nanoparticles in deionized water by using ultrasonic equipment. The mean diameter of TiO 2 nanoparticles was 21 nm. While the thermal conductivity of nanofluids has been measured in general using conventional techniques such as the transient hot-wire method, this work presents the application of the 3ω method for measuring the thermal conductivity. The 3ω method was validated by measuring the thermal conductivity of pure fluids (water, methanol, ethanol, and ethylene glycol), yielding accurate values within 2 %. Following this validation, the effective thermal conductivity of TiO 2 nanoparticles in deionized water was measured at temperatures of 13 • C, 23 • C, 40 • C, and 55 • C. The experimental results showed that the thermal conductivity increases with an increase of particle volume fraction, and the enhancement was observed to be 7.4 % over the base fluid for a nanofluid with 3 % volume fraction of TiO 2 nanoparticles at 13 • C. The increase in viscosity with the increase of particle volume fraction was much more than predicted by the Einstein model. From this research, it seems that the increase in the nanofluid viscosity is larger than the enhancement in the thermal conductivity.A. Turgut · I. Tavman (B)

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This study examined the effects of using different fiber sources [apple pomace powder (APP), carrot pomace powder (CPP) and orange pomace powder (OPP)] on batter rheology and quality characteristics of rice flourbased gluten-free cakes. Gluten-free cake batters were formulated by replacing different amounts of rice flour (0, 5, 10, and 15%) with APP, CPP, and OPP. As a control cake, batters containing no pomace powder were used. The flow behaviors and viscoelastic characteristics of dietary fiber-enriched cake batters were investigated. All cake batters showed shear thinning behavior and the Power Law model was found to explain the flow behavior of all batter formulations. Apparent viscosity, elastic modulus (G 0), and viscous modulus (G 00) of the batter increased with increasing pomace powder content. Furthermore, addition of pomace powder increased batter specific gravity and crumb hardness, and decreased specific volume of cakes. Cakes containing 5% OPP had similar volume index and hardness values to the control sample. The sensory properties of the cake samples were investigated concerning color, texture, appearance, flavor and overall acceptability, and those with 5% OPP received the highest acceptance scores from the panelists.

In most applications, nanoparticles are required to be in a well-dispersed state prior to commercialisation. Conventional technology for dispersing particles into liquids, however, usually is not sufficient, since the nanoparticles tend to form very strong agglomerates requiring extremely high specific energy inputs in order to overcome the adhesive forces. Besides conventional systems as stirred media mills, ultrasound is one means to de-agglomerate nanoparticles in aqueous dispersions. In spite of several publications on ultrasound emulsification there is insufficient knowledge on the de-agglomeration of nanoparticulate systems in dispersions and their main parameters of influence. Aqueous suspensions of SiO2-particles were stressed up to specific energies EV of 10(4) kJ/m3 using ultrasound. Ultrasonic de-agglomeration of nanoparticles in aqueous solution is considered to be mainly a result of cavitation. Both hydrostatic pressure of the medium and the acoustic amplitude of the sound wave affect the intensity of cavitation. Furthermore, the presence of gas in the dispersion medium influences cavitation intensity and thus the effectiveness of the de-agglomeration process. In this contribution both, the influence of these parameters on the result of dispersion and the relation to the specific energy input are taken into account. For this, ultrasound experiments were carried out at different hydrostatic pressure levels (up to 10 bars) and amplitude values (64-123 microm). Depending on the optimisation target (time, energy input,...) different parameters limit the dispersion efficiency and result. All experimental results can be explained with the specific energy input that is a function of the primary input parameters of the process.

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