A combinative use of the photovoltaic modules and roof coating on building was implemented for an institutional hall in Ghana. Computational fluid dynamics simulation was performed for both coated and uncoated roofs to investigate the heat transfer on the roof with regards to the temperature reduction. Numerical results were compared with the field data. The performance of the solar photovoltaic module deployed on the rooftop was evaluated as well. The results demonstrate that the coated roof gives rise to a significant reduction in temperature, which enhances the thermal comfortability in the building. With the participation of the solar photovoltaic module, a total energy of 427.670 MW h/year could be fed into the national grid. The reduction in the power generation cost is accomplished with the joint application of the solar photovoltaic system and the roof coating.
The emphasis of the present study was placed on the impeller of a centrifugal feed pump. A comparative investigation was implemented between three impeller schemes, one with ten equal-length blades and the other with five long and five short blades. Numerical simulation was performed to investigate the flow field associated with the three schemes. Flow patterns were considered. Pressure fluctuations at the impeller outlet and the volute channels were monitored. The validity of the numerical approach was proved with a comparison between experimental data and the numerical result for the scheme with equal-length blades. The results show that the relative deviation of pump head is less than 5% between the three impeller schemes. Meanwhile, the pump efficiency manifests a slight difference. The improvement of flow quality in the impeller eye area is accomplished as half of the blades are shortened. For the scheme with equal-length blades, the pressure fluctuations with the blade passing frequency are distinct both at the impeller outlet and in the volute channels. In comparison, the schemes with five long and five short blades are characterized by weakened blade passing frequency. Low-frequency components are excited remarkably for the two impellers with long and short blades. The pros and cons of the scheme with long and short blades are explained.
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