Planted roofs have been investigated as a passive cooling technology for energy efficiency purposes in buildings. More quantitative data on this topic are required to solve a lack of information for many specific regions. This study is focused on a numerical investigation of the thermal comfort inside a green roof rectangular ventilated cavity in a hot and humid climate like the one of Lomé in west Africa. The left vertical is heated and partly saturated with water to provide humidification of the indoor air. Transfer dimensionless equations are solved using an implicit finite difference scheme, the Thomas algorithm, and the Gauss-Seidel iterative method. We analyze the effects of inlet airflow on the thermal process inside the ventilated and planted enclosure have been investigated. The comfort temperature range deduced from the data is 25°C < Tc < 27°, and that of the indoor air humidity is 49% < Hr <60%. The different ranges obtained are significant and lead to improving inside thermal comfort. The solar flux of 350 W.m -2 , the average value in the case of Lomé city, was used to establish a heat transfer correlation to predict heat transfer through the roof with a relative error not exceeding 4%. This model can be very useful for engineers in the design and optimization stage of a green roof in practical buildings.
Natural convection in integrated wind tower into a high storied building is numerically investigated by solving natural convection equations with the Boussinesq approximation. The present investigation deals with velocity and temperature distribution in a wind tower integrated into a high building divided into three stories; in which the upper horizontal heated wall is vented by a fresh air jet entranced by the wind tower and hot waste air exits from different outlet openings. The purpose of this study is to evaluate the Performance of integrated wind tower into the storied building, thus providing a wind and buoyancy factors for induced natural ventilation to drive air flow through the floors. Numerical solutions of the Navier Stokes equations and energy equation have been solved by the Thomas’ algorithm. Solutions are presented for various geometrical aspect ratios and for different values of Grashof and Reynolds numbers. The results are presented in terms of streamlines, isotherms, velocity, and heat transfer intensity versus the governing control parameters in detail.
This paper presents a small review on the technological advances made on the perovskite-based solar cell. Through this summary of the results of the research on perovskite, the reader will have an overview of the perovskite material, the different structures of a perovskite solar cell, and the opto-electrical properties of such cell as well as the electrical models used in its simulation. Finally, the paper presents in a very brief way the challenges that this technology will have to overcome before finding its place in the photovoltaic market.
Vegetation cover provides shading and protects the soil beneath them from warming. Vegetation can be used as passive cooling technique that reduces the thermal load of a building. A numerical study has been carried out on laminar double-diffusive mixed convection in a green roof enclosure. The model is equipped with inlet and outlet openings for air removal while the left vertical wall is heated and partially saturated with water for indoor air humidification. The mathematical model is governed by the two-dimensional continuity, momentum, energy and concentration equations. Transfer equations are solved using a finite difference scheme and Thomas algorithm. The model was applied for the simulation of a building with green roof in Togolese climate conditions. Results showed that, the flow structure is a mixed convection type, but the isotherms et iso-concentration distributions reveal a vertical stratification of the temperatures and the relative humidity.To predict heat transfers inside the cavity, a correlation has been established for the estimation of the average Nusselt number as a function of the Leaf Area Index and Reynolds number under solar heat flux of 350 W.m-2, the average in case of Togo. It was found that a larger Leaf Area Index reduces the solar flux penetration and therefore, reduces significantly heat transfer inside the enclosure and then stabilizes it temperature. For the LAI equal to 3, the indoor air fluctuates around 26°C and the relative humidity range is found to be 50% - 60% under solar heat flux of 350 W.m-2.
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