Double-Diffusive Natural Convection in a Mixture-Filled Cavity with Walls' Opposite Temperatures and Concentrations

Koufi, Lounes; Chérif, Y.; Younsi, Zohir; Naji, Hassane

doi:10.1080/01457632.2018.1460928

Cited by 22 publications

(12 citation statements)

References 40 publications

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“…To check and validate our approach, the ventilated cavity under thermal buoyancy force and low-turbulent regime reported by [18] was solved. To avoid overloading the text, note that the verification and validation processes have already been presented in previous work [21][22][23][24], with satisfactory results. Likewise, the check process was completed via the problem addressed by Ampofo and Karayiannis [25].…”

Section: Numerical Validationmentioning

confidence: 86%

Numerical simulation of the CO2 diffusion effect on low turbulent mixed convection in a ventilated room heated by the bottom

2021

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A double-diffusive mixed convection within low-turbulent regime in a ventilated cavities filled with an air-CO2 mixture and heated from below has been numerically investigated. The lower wall was sustained at a uniform temperature and CO2-concentration. The vertical and upper walls were kept at external temperature and CO2-concentration. To analyze the behavior of flow, the ventilation effectiveness for temperature distribution and removal of CO2-contaminant, four configurations were dealt. These differ from each other by the location of the mixture inlet and outlet gaps. Likewise, three CO2-concentrations were considered (103, 2x103 and 3x103 ppm) to investigate the influence of the CO2-diffusion on the ventilation effectiveness. The numerical simulations were performed by considering closed Reynolds averaged-Navier-Stokes (RANS) equations using the Re-Normalization Group k-? model. The governing equations' set was then solved using the finite volume method, in which the pressure-velocity coupling was handled using the SIMPLEC algorithm. Validation of the numerical model was achieved by comparing our results with available experimental data. The obtained results indicate that the CO2-diffusion effect on the air movement and the ventilation effectiveness for temperature distribution can be neglected in the present study. However, the CO2-diffusion remains a key parameter in terms of indoor air quality index. Also, it was found that one of the studied configurations provides a better ventilation effectiveness to remove heat and CO2-contaminant, and insures a homogeneous temperature and CO2-concentration in the occupied zone. The three other configurations maintain an acceptable level of heat and can be used in temperate climate to ensure good indoor air quality.

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Section: Numerical Validationmentioning

confidence: 86%

Numerical simulation of the CO2 diffusion effect on low turbulent mixed convection in a ventilated room heated by the bottom

2021

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“…For more details, the interested reader can refer to Refs. (Koufi et al , 2017; Koufi et al , 2018).…”

Section: Numerical Details and Methods Of Solutionmentioning

confidence: 99%

Numerical study of the effects of ventilated cavities outlet location on thermal comfort and air quality

Younsi

Koufi

Naji

2019

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Purpose A comprehensive investigation on the outlet air position effects on the thermal comfort and air quality has been achieved. In addition, airflow and temperature distributions in ventilated cavities filled with an air-CO2 mixture with mixed convection are predicted. The airflow enters from the cavity through an opening in the lower side of the left vertical wall and exits through the opening in one wall of the cavity. This paper aims to investigate the outlet location effect, four different placement configurations of output ports are considered. Three of them are placed on the upper side and the fourth on top of the opposite side of the inlet opening. A uniform heat and CO2 contaminant source are applied on the left vertical wall, while the remaining walls are impermeable and adiabatic to heat and solute. The cooling efficiency inside the enclosure and the average fluid temperature are computed for different Reynolds and Rayleigh numbers to find the most suitable fluid outlet position that ensures indoor comfortable conditions while effectively removing heat and the contaminant. This is demonstrated by three relevant indices, namely, the effectiveness for heat removal, the contaminant removal and the index of indoor air quality. Design/methodology/approach The simulations were performed via the finite-volume scSTREAM CFD solver V11. Three different values of CO2 amount are considered, namely, 103, 2 × 103 and 3 × 103 ppm, the Reynolds number being in the range 100 ≤ Re ≤ 800. Findings Based on the findings obtained, it is the configuration whose air outlet is placed near the heat source and the contaminant, which provides a better air distribution and a ventilation efficiency compared to the others ventilation strategies. Originality/value The studies on heat and mass transfers by natural and forced convection in ventilated cavities remain a fruitful research topic. Thereby, such a study deals with different ventilation strategies through cavities containing an air-CO2 mixture subjected to a mixed regime. In particular, the air inlet velocity and contaminant sources’ effects on thermal comfort and air quality have been investigated.

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“…The code has been verified by comparing our results with those available in the literature. 20,[33][34][35][36] Results for the problem of the pure natural convection for a large temperature gradients and for the problem of the double-diffusive convection for a low temperature and solutal concentration gradients are compared with those obtained by 33,34 and, 20,35,36 respectively. For the case of thermal convection for large temperature gradients, calculations were carried out for air initially at temperature T 0 ¼ 600 K and for Ra ¼ 10 6 and e T ¼ 0:6.…”

Section: Validationmentioning

confidence: 99%

Limit of the buoyancy ratio in Boussinesq approximation for double-diffusive convection in binary mixture

2021

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This paper deals with a mathematical and numerical investigation of double-diffusive natural convective heat and mass transfer in a cavity filled with Newtonian fluid with significant density and mass diffusivity changes. In such a situation, the assumption of the Boussinesq approximation is not justified, and an appropriate model based on a set of Low Mach Number equations is used. The active parts of two vertical walls of the cavity are maintained at fixed but different temperatures and concentrations, while the other two walls, as well as inactive areas of the sidewalls, are considered to be adiabatic and impermeable to mass transfer. The coupled momentum, energy, and solute transfer equations in binary mixtures of ideal gases are solved through a global iterative procedure based on the finite volume methods in the context of the low Mach number approximation. The study includes the effect of the buoyancy ratio N with the aim to find its application limit in the Boussinesq conditions. The results show that if we use the Boussinesq approximation to study double-diffusive convection, the value of parameter N must be between À6 and 27.M Ã þC10ð1ÀM Ã Þ kinematic viscosity, m 2 =s P ¼ðp À p þ q 0 gyÞ=q 0 ða 0 =HÞ 2 dimensionless dynamic pressure

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Double-Diffusive Natural Convection in a Mixture-Filled Cavity with Walls' Opposite Temperatures and Concentrations

Cited by 22 publications

References 40 publications

Numerical simulation of the CO2 diffusion effect on low turbulent mixed convection in a ventilated room heated by the bottom

Numerical simulation of the CO2 diffusion effect on low turbulent mixed convection in a ventilated room heated by the bottom

Numerical study of the effects of ventilated cavities outlet location on thermal comfort and air quality

Limit of the buoyancy ratio in Boussinesq approximation for double-diffusive convection in binary mixture

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