On numerical modelling of conjugate turbulent natural convection and radiation in a differentially heated cavity

Wu, Ting; Lei, Chengwang

doi:10.1016/j.ijheatmasstransfer.2015.07.113

Cited by 73 publications

(13 citation statements)

References 26 publications

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“…The realizable k-ε turbulence model was used because it exhibits strong performance with indoor airflows, temperature, and pressure in closed structures (Sørensen and Nielsen, 2003;Bacharoudis et al, 2007;Piña-Ortiz et al, 2014;Wu et al, 2015). Enhanced wall treatment and a full buoyancy effect were considered in the turbulence model.…”

Section: Turbulence Modelmentioning

confidence: 99%

Air quality control in mine refuge chamber with ventilation through pressure air pipeline

zhang

Wang

et al. 2020

Process Safety and Environmental Protection

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A combined experimental and numerical study was performed to improve the performance of the ventilation system in a mine refuge chamber (MRC). In the experiment, CO2 cylinders and dispersion pipes were used to simulate the CO2 release of 50 people, and 0.1 L/min per person of fresh air was provided by an air compressor. A new analytical model for a 50-person MRC was proposed and validated against the experimental data. Sensitivity analysis was carried out to investigate the effects of several control factors. The results indicated the following: (1) The ventilation system layout has a significant influence on the CO2 concentration distribution in an MRC, while the uniformity of the CO2 concentration distribution in the MRC may not be effective with increased number of air inlets. (2) Under a well-arranged ventilation system in the 50-person MRC, the average CO2 concentration can be controlled at less than 0.5% with a ventilation rate of 0.1 m 3 /min per person, and less than 0.2% with a ventilation rate of 0.3 m 3 /min per person. (3) A quantitative correlation exists between the CO2 concentration and ventilation volume rate, as well as the CO2 release rate, for an MRC under a well-arranged ventilation system.

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Section: Turbulence Modelmentioning

confidence: 99%

Air quality control in mine refuge chamber with ventilation through pressure air pipeline

zhang

Wang

et al. 2020

Process Safety and Environmental Protection

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“…SST k- (Wu and Lei, 2015) 56 Table 2 presents the mean convection, radiation and total Nusselt numbers for different grid values for Ra=10 9 , Pl=0.02 and =0. Variation in the number of grid points from 200×200 with stretching ratio 1.05 to 400×400 with stretching ratio 1.05 affects the mean total, radiative and convection Nusselt number by less than 0.01%, 0.0% and 0.02%, respectively.…”

Section: Numerical Solutionmentioning

confidence: 99%

İzotropi̇k Saçilma Ortamli Kare Geometri̇ İçi̇nde Türbülansli Doğal Taşinim Ve Işinim Isi Transferi̇

Tekkalmaz

2020

Isı Bilimi Ve Tekniği Dergisi

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The influence of turbulent natural convection and thermal radiation in a differentially heated square enclosure is numerically investigated. The enclosure is heated from the right wall and cooled from the left wall. The other walls are assumed to be adiabatic. The Reynolds Averaged Navier Stokes (RANS) formulation was employed for analyzing turbulent flows together with a Realizable k- model. In addition, the discrete ordinates method (DOM) was used to solve the radiative transfer equation (RTE). Influence of Rayleigh number (Ra), optical thickness (), Planck number (Pl), scattering albedo () and wall emissivity (w ) parameters were studied numerically on square enclosure for the flow and temperature distribution. It is interesting to note that a detailed parametric study focusing on characterizing parameters in turbulent natural convection and radiation was rarely dealt with in details. Solutions were obtained for a range of Rayleigh numbers varying from 10 9 to 10 12. It was found that the radiation heat transfer alters the characteristics of flow fields in the enclosure. Increasing the optical thickness results in a decrease in combined heat transfer for a fixed Rayleigh number and the maximum of heat transfer occurred for low optical thickness with radiation presence. t Nu =87.796 and 82.351 is obtained for =0.2 and 5, respectively (Ra=10 10 , Pl=0.02 and =0). The heat transfer increases with decreasing Planck number, and decreases with the increasing scattering albedo. t Nu =445.837 and 68.100 is obtained for Pl=0.001 and 10, respectively (Ra=10 10 , =1 and =0). When the active walls are black and the insulated walls are reflected, t Nu =85.507 is obtained for Ra=10 10 , Pl=0.02, =1 and =0.

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“…It can be seen from A realizable k-ε turbulent model will be used since it is known to have a good performance with indoor airflows, temperature and pressure in closed structures. [41][42][43][44][45] In the turbulence model, the enhanced wall treatment with pressure gradient effects and thermal effects, and the full buoyancy effect under gravity have been taken into account, but the viscous heating is ignored since the air flows in the living room at a low speed and there is almost no mechanical energy be converted into heat.…”

Section: Computational Model and Meshmentioning

confidence: 99%

Thermal performance of a mine refuge chamber with human body heat sources under ventilation

Zhang

Wang

et al. 2019

Applied Thermal Engineering

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This paper investigated the dynamic coupling heat transfer characteristics of rock and air in a Mine Refuge Chamber (MRC) under ventilation. In the current work, a comprehensive fiftyperson MRC model combining human-body heat sources and ventilation is established, the proposed model is validated against available experimental data with deviation less than 4%. Furthermore, sensitivity analysis is performed to investigate the influence of several control parameters such as heating rate, ventilation and wall area in a MRC through using numerical simulation. Results indicated that: (ⅰ) the heat transfer process in a MRC will reach a stage of air temperature slow increase (ATSI) in less than 0.5 h. The air temperature rises linearly with the square root of time during the ATSI stage; (ⅱ) for a MRC built in a sandstone seam with an initial rock temperature of less than 27 °C, the average air temperature will not exceed 35 °C in 96 h when the ventilation volume rate is 0.3 m 3 /min per person; (ⅲ) the rate of temperature rise in MRC is proportional to the rate of heat generation, but it is inversely proportional to the thermal conductivity, density and thermal capacity of the rock, as well as the ventilation volume rate and the wall area; (ⅳ) an empirical correlation for the MRC average air temperature is developed while the supply air temperature equals to the initial rock temperature. Keywords：Underground; Mine refuge chamber; Air temperature prediction; Ventilation; Heat transfer coefficient; Human body heat sources. Nomenclature a Constant in K expression V Ventilation volume for MRC, m 3 /h A w Wall area of MRC, m 2 x, y Coordinate direction vector b Constant in K expression Subscripts B Temperature variable, °C a Air c Constant in K expression num Numerical data C a Specific heat capacity of air, J/(kg• K) exp Experimental data C p Specific heat capacity of rock, J/(kg• K) Greek symbols d Constant in K expression α Surface heat transfer coefficient, W/(m 2 • K) i, j Constant in B expression Θ Difference k Constant in B expression ρ Density of rock, kg/m 3 K Rate for air temperature increasing, °C/s 0.5 ρ a Density of air, kg/m 3 l Constant in B expression λ Thermal conductivity of rock, W/(m• K) L Temperature variable, °C τ Heat time, h L c Perimeter of cross-section tunnel, m Acronyms m, n Constant in K expression ATSI Air temperature slow increase p Pressure, Pa CE Critical equilibrium Q Total heat generation rate in MRC, W MRC Mine refuge chamber r 0 equivalent radius of cross-section tunnel, m MMRC Movable mine rescue capsules T Temperature, °C PCM Phase change materials T 0 Initial rock temperature, °C

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On numerical modelling of conjugate turbulent natural convection and radiation in a differentially heated cavity

Cited by 73 publications

References 26 publications

Air quality control in mine refuge chamber with ventilation through pressure air pipeline

Air quality control in mine refuge chamber with ventilation through pressure air pipeline

İzotropi̇k Saçilma Ortamli Kare Geometri̇ İçi̇nde Türbülansli Doğal Taşinim Ve Işinim Isi Transferi̇

Thermal performance of a mine refuge chamber with human body heat sources under ventilation

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