Thermal Efficiency of a Hybrid Photovoltaic-thermal Chimney Integrated into a Building
Yawovi Nougbléga,
Kodjo Kpode,
Kokou N’Wuitcha,
Malgolmèèna Banna
Issue:
Volume 8, Issue 4, July 2019
Pages:
50-65
Received:
12 August 2019
Accepted:
2 September 2019
Published:
19 September 2019
Abstract: The solar photovoltaic-thermal energy, it is a combination of Photovoltaic (PV) and solar thermal components integrated into one system and enables to generate electricity and heat simultaneously. The solar chimney can generate air flow through the living space of the building to provide cooling. Hence, there is a greater interest to study the mixed convection in the hybrid Photovoltaic-Thermal chimney integrated into buildings for natural room ventilation for thermal comfort. The thermal efficiency has been studied by analysing numerically the mixed convection in the hybrid photovoltaic-thermal chimney integrated into the building in the present paper. The stream fucntion-vorticity formulation with a finite difference numerical discretization solution scheme have been adopted. The system of algebraic governing equations is solved by Thomas algorithm method. The aim of the present paper is to study and to predict the dynamic fields and particularly of the mass flow rate of the air thermosiphon drawing in the hybrid Photovoltaic-Thermal chimney integrated into a building for passive cooling in the room. The effects of the governing parameters, particularly Grashof number (103 ≤ Gr ≤ 106), that depends of the solar radiation intensity in the region, the mass flow rate of the inlet fresh air (0.001 Kg.s-1 ≤ Dm ≤ 0.3Kg.s-1), the integrated chimney width on fluid flow and the heat transfer characteristics are studied in detail. Passive cooling and the electrical efficiency of the PV solar cells are increasing function of the intensity of the inlet air flow. Due to the possible reduction of cooling loads with the insertion of the photovoltaic cells plate into the chimney integrated into the building. The numerical simulation has been conducted to determine heat transfer, mass flow rate trough the chimney exit, solar cells PV efficiency and the effect of design parameters of the room and the integrated hybrid Photovoltaic-Thermal chimney to make the bioclimatic building energy autonomy. The outlet velocity, streamlines, isotherms, Nusselt number along the active walls, and the mass flow rate are plotted versus the above controlling parameters.
Abstract: The solar photovoltaic-thermal energy, it is a combination of Photovoltaic (PV) and solar thermal components integrated into one system and enables to generate electricity and heat simultaneously. The solar chimney can generate air flow through the living space of the building to provide cooling. Hence, there is a greater interest to study the mixe...
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Atomic Form Factor Calculations of S-states of Helium
Saïdou Diallo,
Ibrahima Gueye Faye,
Louis Gomis,
Moustapha Sadibou Tall,
Ismaïla Diédhiou
Issue:
Volume 8, Issue 4, July 2019
Pages:
66-71
Received:
12 September 2019
Accepted:
4 October 2019
Published:
15 October 2019
Abstract: Variational calculations of the helium atom states are performed using highly compact 26-parameter correlated Hylleraas-type wave functions. These correlated wave functions used here yield an accurate expectation energy values for helium ground and two first excited states. A correlated wave function consists of a generalized exponential expansion in order to take care of the correlation effects due to N-corps interactions. The parameters introduced in our model are determined numerically by minimization of the total atomic energy of each electronic configuration. We have calculated all integrals analytically before dealing with numerical evaluation. The 1S2 11S and 1S2S 21, 3S states energies, charge distributions and scattering atomic form factors are reported. The present work shows high degree of accuracy even with relative number terms in the trial Hylleraas wave functions definition. The results presented here, indicate that the highly compact twenty-six variational parameters model will have the quantitative and qualitative applicability for the study of electronic correlation. The correlated wave functions are used to calculate the atomic form factor for the diffusion of electrons by the helium atom. The atomic form factor is evaluated as the Fourier transform of the electron density distribution of an atom or ion, which is calculated from theoretical correlated wave functions for free atoms. Finally, suggestions are made as to the way the atomic form factor of the helium atom may be approximated by a sum of Gaussians for efficiency use.
Abstract: Variational calculations of the helium atom states are performed using highly compact 26-parameter correlated Hylleraas-type wave functions. These correlated wave functions used here yield an accurate expectation energy values for helium ground and two first excited states. A correlated wave function consists of a generalized exponential expansion ...
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