A square with a thermal square column is a simple but nontrivial research prototype for nanofluid research. However, until now, the effects of the temperature of the square column on the heat and mass transfer of nano...A square with a thermal square column is a simple but nontrivial research prototype for nanofluid research. However, until now, the effects of the temperature of the square column on the heat and mass transfer of nanofluids have not been revealed comprehensively, especially on entropy generation. To deepen insight into this important field, the natural convection of the SiO2-water nanofluid in a square cavity with a square thermal column is studied numerically in this study. The effects of the thermal column temperature （T = 0.0, 0.5, 1.0, 1.5）, the Rayleigh number （ranging from 103 to 106）, and the volume fraction of the nanoparticle （varying from 0.01 to 0.04） on the fluid flow, heat transfer, and entropy generation are investigated, respectively. It is found that, no matter at a low or high Rayleigh number, the volume fraction of the nanoparticle shows no considerable effects on the flow field and temperature field for all the temperatures of the thermal column. With an increase in the volume fraction, the mean Nusselt number increases slightly. At the same time, it is found that, with an increase in the temperature of the thermal column, the average Nusselt number gradually decreases at all values of the Rayleigh number. Meanwhile, it is found that, at a high Rayleigh number, the heat transfer mechanism is the main parameter affecting the increase in the total entropy generation rather than the volume fraction. In addition, no matter at a high or low Rayleigh number, when T = 0.5, the total entropy generation is the minimum.展开更多
The dynamic wetting of water spreading on TiO 2 and TiO 2 SiO 2 films prepared by sol gel method and subsequently treated by air plasma and UV irradiation was investigated. Water completely spread on TiO 2 surface wit...The dynamic wetting of water spreading on TiO 2 and TiO 2 SiO 2 films prepared by sol gel method and subsequently treated by air plasma and UV irradiation was investigated. Water completely spread on TiO 2 surface within 3 s and its dynamic contact angles can be expressed by a power law θ d= k(t+a) -n with the n value 0.98. Less than 50%(molar fraction) SiO 2 addition can accelerate the dynamic water spreading rate on the TiO 2 SiO 2 films and the optimum molar fraction of SiO 2 amount corresponding to as annealed, air plasma, and UV irradiation treatment process is 15%, 10% and 20%, respectively.展开更多
基金Project supported by the National Natural Science Foundation of China(No.51176061)the Universidad Carlos III de Madrid,the European Union’s Seventh Framework Programme for Research,Technological Development and Demonstration(No.600371)+1 种基金el Ministerio de Economíay Competitividad(No.COFUND2014-51509)el Ministerio de Educacíon,Culturay Deporte(No.CEI-15-17)
文摘A square with a thermal square column is a simple but nontrivial research prototype for nanofluid research. However, until now, the effects of the temperature of the square column on the heat and mass transfer of nanofluids have not been revealed comprehensively, especially on entropy generation. To deepen insight into this important field, the natural convection of the SiO2-water nanofluid in a square cavity with a square thermal column is studied numerically in this study. The effects of the thermal column temperature （T = 0.0, 0.5, 1.0, 1.5）, the Rayleigh number （ranging from 103 to 106）, and the volume fraction of the nanoparticle （varying from 0.01 to 0.04） on the fluid flow, heat transfer, and entropy generation are investigated, respectively. It is found that, no matter at a low or high Rayleigh number, the volume fraction of the nanoparticle shows no considerable effects on the flow field and temperature field for all the temperatures of the thermal column. With an increase in the volume fraction, the mean Nusselt number increases slightly. At the same time, it is found that, with an increase in the temperature of the thermal column, the average Nusselt number gradually decreases at all values of the Rayleigh number. Meanwhile, it is found that, at a high Rayleigh number, the heat transfer mechanism is the main parameter affecting the increase in the total entropy generation rather than the volume fraction. In addition, no matter at a high or low Rayleigh number, when T = 0.5, the total entropy generation is the minimum.
文摘The dynamic wetting of water spreading on TiO 2 and TiO 2 SiO 2 films prepared by sol gel method and subsequently treated by air plasma and UV irradiation was investigated. Water completely spread on TiO 2 surface within 3 s and its dynamic contact angles can be expressed by a power law θ d= k(t+a) -n with the n value 0.98. Less than 50%(molar fraction) SiO 2 addition can accelerate the dynamic water spreading rate on the TiO 2 SiO 2 films and the optimum molar fraction of SiO 2 amount corresponding to as annealed, air plasma, and UV irradiation treatment process is 15%, 10% and 20%, respectively.
