A Comprehensive Physical Profile for Aqueous Dispersions of Carbon Derivatives as Solar Working Fluids

Abstract

The application of nanofluids in direct solar absorption, heat transfer or direct solar steam generation entails carrying out a comprehensive study taking into account several physical quantities. Long-term stability, rheological, thermophysical and optical properties of dispersions must be known to assess their potential for envisaged applications. Two low-concentration nanofluids, 0.005 and 0.05 wt%, of sulfonic acid-functionalized and polycarboxylate chemically modified graphene nanoplatelets in water were considered in this work. Elemental analyses of the nanopowders and pH evaluations of the colloids were carried out. The rheological behaviour of dispersions at different temperatures was studied by rotational rheometry. Thermal conductivities were measured by the transient hot wire method and densities by the oscillating U-tube technique. Additionally, a brief report of the optical properties was included to provide a comprehensive physical analysis.

Optical Limiting of Carbon Nanohorn-Based Aqueous Nanofluids: A Systematic Study

“…Differently, at 355 nm, better optical limiting properties were observed for higher nanoparticle concentrations, as shown in Figure 6. This behavior agrees with that reported in the literature for carbon nanotubes [25], graphite/nanodiamond mixtures [26], functionalized graphene nanoplatelets [27,28] and gold nanoparticles [29] and can be explained in terms of the light-induced creation of bubbles within the fluid. In fact, under the effect of light irradiation, nanoparticles become localized heat sources within the fluid, ultimately producing vaporization of the surrounding fluid layers and/or ionization and expansion of nanostructures themselves.…”

Моделювання Процесів Теплообміну В Мікромеханічних Перетворювачах На Основі Добавок Наночасток Графена

“…Проведені розрахунки показали, що більшим значенням теплопровідності відповідають нижчі максимальні температури графенового шару, а збільшення потужності теплового потоку призводить до збільшення максимальної температури. Для мінімального джерела теплоти (0,5 мВт) мак-симальне значення температури майже однаково при будь-якій з конфігурацій листів графену [6].…”

Enhanced Heat Transfer Performance of the Tube Heat Exchangers Using Carbon-Based Nanofluids

“…HTC P pe (10) The PI e of the test sample for the THE system at various experimental parameters is shown in Figure 10. In terms of the overall average value, the PI e of 0.05 wt% and 0.2 wt% CBNF at a heating power of 80 W was 1.72% and 1.54% higher than that of water, respectively, while the PI e of 0.05 wt% and 0.2 wt% CBNF at a heating power of 120 W was 4.04% and 1.42% higher than that of water, respectively.…”

“…In particular, CNTs and graphene have received great attention because of their large aspect ratio, and special optical, mechanical, physical, and chemical properties. Therefore, CBNFs have been commonly used in heat exchange, thermal storage, and thermal collection systems to improve system performance [6][7][8][9][10]. In addition, high-performance CBNFs should have considerable potential in the application of relevant cutting-edge technologies in the future [11].…”