Extension of the zonal method to inhomogeneous non-grey semi-transparent medium

Méchi, Rachid; Farhat, Habib; Guedri, Kamel; Halouani, Kamel; Saïd, Rachid

doi:10.1016/j.energy.2009.06.040

Cited by 24 publications

(7 citation statements)

References 42 publications

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“…Leaving fluxes were calculated using the method of LU decomposition [26]. TEA and DEA were corrected using the generalized Lawson's smoothing method [27]. The DFA were determined as defined in [9].…”

Section: Resultsmentioning

confidence: 99%

Influence of the gray gases number in the weighted sum of gray gases model on the radiative heat exchange calculation inside pulverized coal-fired furnaces

Crnomarković¹,

Belošević²,

Tomanović³

et al. 2016

THERM SCI

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The influence of the gray gases number in the weighted sum in the gray gases model on the calculation of the radiative heat transfer is discussed in the paper. A computer code which solved the set of equations of the mathematical model describing the reactive two-phase turbulent flow with radiative heat exchange and with thermal equilibrium between phases inside the pulverized coal-fired furnace was used. Gas-phase radiative properties were determined by the simple gray gas model and two combinations of the weighted sum of the gray gases models: one gray gas plus a clear gas and two gray gases plus a clear gas. Investigation was carried out for two values of the total extinction coefficient of the dispersed phase, for the clean furnace walls and furnace walls covered by an ash layer deposit, and for three levels of the approximation accuracy of the weighting coefficients. The influence of the number of gray gases was analyzed through the relative differences of the wall fluxes, wall temperatures, medium temperatures, and heat transfer rate through all furnace walls. The investigation showed that there were conditions of the numerical investigations for which the relative differences of the variables describing the radiative heat exchange decrease with the increase in the number of gray gases. The results of this investigation show that if the weighted sum of the gray gases model is used, the complexity of the computer code and calculation time can be reduced by optimizing the gray gases number.

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Section: Resultsmentioning

confidence: 99%

Influence of the gray gases number in the weighted sum of gray gases model on the radiative heat exchange calculation inside pulverized coal-fired furnaces

Crnomarković¹,

Belošević²,

Tomanović³

et al. 2016

THERM SCI

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“…Accuracy of the HZM is based on accuracy of determination of total exchange areas. Various methods were developed for determination and improvement of total exchange areas [17,18].…”

Section: »1=1 »=1mentioning

confidence: 99%

Influence of application of Hottel’s zonal model and six-flux model of thermal radiation on numerical simulations results of pulverized coal fired furnace

et al. 2012

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Difference of results of numerical simulation of pulverized coal fired fitrnace when mathematical models contain various radiation models has been described in the paper. Two sets of numerical simulations of pulverized coal fired furnace of 210 MW^ power boiler have been performed. One numerical simulation has contained Hottel's zonal model, whereas the other numerical simulation has contained six-fiux model. Other details of numerical simulations have been identical. The infiuence of radiation models has been examined through comparison of selected variables (gas-phase temperature, oxygen concentration, and absorbed radiative heat rate of surface zones of rear and right furnace walls), selected global parameters of furnace operation (total absorbed heat rate by all furnace walls and furnace exit gas-phase temperature). Computation time has been compared as well. Spatially distributed variables have been compared through maximal local differences and mean differences. Maximal local difference of gas-phase temperature has been 8.44%. Maximal local difference of absorbed radiative heat rate of the surface zones has been almost 80.0%. Difference of global parameters of furnace operation has been expressed in percents of value obtained by mathematical model containing Hottel 's zonal model and has not been bigger than 7.0%. Computation time for calculation of 1000 iterations has been approximately the same. Comparison with other radiation models is necessary for assessment of differences.

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“…In that or similar way, the zonal method was used for numerical investigations of industrial furnaces [8][9][10], to find incident radiative fluxes on the freeboard walls of a bubbling fluidized bed [11], and for numerical investigations of a pulverized coal-fired furnace [6,12]. Nonclassical applications of the zonal model were described for nonhomogeneous radiatively participating medium [13][14][15][16]. These methods were developed for the black-walled systems [13,14,16], or for nonscattering medium [15], while the walls of pulverized coal-fired furnaces, inside which is a scattering medium, are gray.…”

Section: Introductionmentioning

confidence: 99%

“…Nonclassical applications of the zonal model were described for nonhomogeneous radiatively participating medium [13][14][15][16]. These methods were developed for the black-walled systems [13,14,16], or for nonscattering medium [15], while the walls of pulverized coal-fired furnaces, inside which is a scattering medium, are gray. Papers which describe determination of wall variables by numerical simulations when radiative heat exchange is solved by the zonal model are very rare.…”

Section: Introductionmentioning

confidence: 99%

Determination of the Wall Variables Within the Zonal Model of Radiation Inside a Pulverized Coal-Fired Furnace

Crnomarkovic¹,

Belošević²,

Nemoda³

et al. 2018

FU Mech Eng

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Determination of the wall variables (wall emissivities, wall temperatures, and heat fluxes) when the zonal model of radiation is used in numerical simulations of processes inside a pulverized coal-fired furnaces is described. Two methods for determination of the wall variables, i.e., a repeated run of numerical simulation (RRNS) and a temporary correction of the total exchange areas (TCTEA) are compared. Investigation was carried out for three values of the flame total extinction coefficient and four values of the initial wall emissivities. Differences of the wall variables were determined using the arithmetic means (AMs) of the relative differences. The AMs of the relative differences of the wall variables increased with an increase in the flame total extinction coefficient and changed a little with an increase in the initial values of the wall emissivities. For the selected furnace, the smallest differences of the wall variables were obtained for Kt=0.3 m-1 and ew,in=0.7. Although both methods can be used for determination of the wall variables, the RRNS method was recommended because the manipulation with files was easier for it. mmended because the manipulation with files was easier for it.

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Extension of the zonal method to inhomogeneous non-grey semi-transparent medium

Cited by 24 publications

References 42 publications

Influence of the gray gases number in the weighted sum of gray gases model on the radiative heat exchange calculation inside pulverized coal-fired furnaces

Influence of the gray gases number in the weighted sum of gray gases model on the radiative heat exchange calculation inside pulverized coal-fired furnaces

Influence of application of Hottel’s zonal model and six-flux model of thermal radiation on numerical simulations results of pulverized coal fired furnace

Determination of the Wall Variables Within the Zonal Model of Radiation Inside a Pulverized Coal-Fired Furnace

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