Radiative entropy generation in a gray absorbing, emitting, and scattering planar medium at radiative equilibrium

Sadeghi, Pegah; Ali, Saad

doi:10.1016/j.jqsrt.2017.06.023

Cited by 18 publications

(5 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Hinojosa et al showed that for an open cavity with an isothermal heat source, the total dimensionless rate of entropy generation increases with increase in emissivity; that is a difference with isoflux heat source. Sadeghi and Safavinejad also showed that for a mixed boundary condition (constant heat flux and constant temperature at two planes) in a planar medium with radiative equilibrium, as the emissivity of wall increases, the entropy generation rate at wall decreases slightly.…”

Section: Resultsmentioning

confidence: 97%

Optimal design with entropy generation minimization approach in combined natural convection with surface radiation in a two‐dimensional enclosure

Dashti

Ali

2019

Heat Trans. Asian Res.

Self Cite

View full text Add to dashboard Cite

Analysis of combined natural convection with surface radiation in a two-dimensional enclosure is carried out. To search the optimal location of the heat source, the entropy generation minimization approach and conventional heat transfer parameters are used and compared. Air is considered as an incompressible fluid and transparent media filling the enclosure with a steady and laminar regime. The enclosure internal surfaces are also gray, opaque, and diffused. The governing equations are solved using the finite difference approach. The results show that with increase in emissivity, entropy generation decreases, and as the Rayleigh number increases, the rate of entropy generation increases. Furthermore, optimum design with the maximum dimensionless temperature and convective Nusselt number confirms the applicability of the second law for optimal design. K E Y W O R D S constant flux heat source, entropy generation minimization, natural convection, optimal search, surface radiation

show abstract

Section: Resultsmentioning

confidence: 97%

Optimal design with entropy generation minimization approach in combined natural convection with surface radiation in a two‐dimensional enclosure

Dashti

Ali

2019

Heat Trans. Asian Res.

Self Cite

View full text Add to dashboard Cite

show abstract

“…During their experiments in the 1930s, Hottel and his collaborators considered the emission of radiation from a hemispherical mass of gas toward a small surface element located in the center of the base of the hemisphere. It is evident that it is convenient to extend the emissivity data reported to masses of gases of other geometric configurations and this is carried out by introducing the concept of characteristic or mean beam length L , which represents the radius of an equivalent hemisphere 24–26 …”

Section: Methodsmentioning

confidence: 99%

“…It is evident that it is convenient to extend the emissivity data reported to masses of gases of other geometric configurations and this is carried out by introducing the concept of characteristic or mean beam length L, which represents the radius of an equivalent hemisphere. [24][25][26] The AS that allows obtaining the spectral emissivity of the participating gaseous medium is then a function of the product of the characteristic length of the beam L, the partial pressure of the participating component and the view factor between the leaving and reaching surfaces (see Figure 1), being described by the following mathematical relationship 27 :…”

Section: Characteristic Length or Average Length Of The Beammentioning

confidence: 99%

Radiant energy exchange through participating media composed of arbitrary concentrations of H₂O, CO₂, and CO

Camaraza‐Medina,

Hernandez‐Guerrero,

Luviano‐Ortiz

2024

Heat Trans

View full text Add to dashboard Cite

In this work, an approximate analytical solution (AS) is presented to evaluate the radiative thermal exchange through a gaseous participating medium composed of H2O, CO2, and CO, which is valid for the product values of pressure path‐length (PL) from 0.06 to 20 atm m and temperatures (T) from 300 K to 2100 K. The Spence root weighting method is used to approximate the exact solutions. For each set of , the value of exact spectral emissivity and absorptivity and for the gas mixture is calculated using the AS, the Hottel graphical method (HGM) and the proposed approximate solution. The weaker adjustment was achieved in the modeling of the HGM, with a mean deviation obtained of ±15% and ±20% for 43.8% and 56.3% of the data evaluated, respectively, while the best indices were obtained in the estimation of the proposed method, with a mean deviation obtained of ±10% and ±15% for 81.3% and 98.1% of the available data, respectively. In all cases, the agreement of the proposed model with the available experimental data is good enough to be considered satisfactory for practical design.

show abstract

“…Therefore, emissivity is a complex function that involves the volume of the gas mixture, the partial pressure of each component of the mixture P x , the average temperature of the mixture, the product of the spectral absorption coefficient of the medium k λ , the view factor F 12 and L. 25,26 Due to its high complexity, the use of Equation ( 1) in engineering practice is null. Generally, for practical calculations, the generalization of approximate experimental values of L is preferred.…”

Section: Mean Beam Lengthmentioning

confidence: 99%

Gas emissivities and absorptivities for H₂O–CO₂–CO mixtures

Camaraza‐Medina

2024

Heat Trans

View full text Add to dashboard Cite

In this work, an approximate solution is given to compute the gas emissivities and absorptivities for H2O–CO2–CO mixtures. The proposed model is valid for temperatures from 300 to 2700 K and pressure path‐length from 0.06 to 40 atm m. In the calculation of the analytical solution (AS), the nonlinear methods of Galerkin and Ritz were implemented based on the residual solution of the differential roots of the Finite Element Method. For each point value using the AS, the spectral absorptivity and emissivity were determined, while for the gas mixture the emissivity and absorptivity were computed using the Hottel Graphical Method (HGM) and the proposed method. In the emissivity calculations, the HGM shows less adjustment, with values of ±20% and ±15% for 79.1% and 56.2% of the available analytical data, while the proposed model correlates adequately with the available data, showing an average deviation of ±15% and ±10% for 91.4% and 76.2% of the available data. In the absorptivity estimations, the HGM shows a weaker fit, with values of ±20% and ±15% for 77.3% and 51.4% of the experimental data, respectively, while the proposed model shows good agreement with the available data, with a mean deviation of ±15% and ±10% for 89.8% and 74.1% of the test made.

show abstract

Radiative entropy generation in a gray absorbing, emitting, and scattering planar medium at radiative equilibrium

Cited by 18 publications

References 20 publications

Optimal design with entropy generation minimization approach in combined natural convection with surface radiation in a two‐dimensional enclosure

Optimal design with entropy generation minimization approach in combined natural convection with surface radiation in a two‐dimensional enclosure

Radiant energy exchange through participating media composed of arbitrary concentrations of H₂O, CO₂, and CO

Gas emissivities and absorptivities for H₂O–CO₂–CO mixtures

Contact Info

Product

Resources

About

Radiative entropy generation in a gray absorbing, emitting, and scattering planar medium at radiative equilibrium

Cited by 18 publications

References 20 publications

Optimal design with entropy generation minimization approach in combined natural convection with surface radiation in a two‐dimensional enclosure

Optimal design with entropy generation minimization approach in combined natural convection with surface radiation in a two‐dimensional enclosure

Radiant energy exchange through participating media composed of arbitrary concentrations of H2O, CO2, and CO

Gas emissivities and absorptivities for H2O–CO2–CO mixtures

Contact Info

Product

Resources

About

Radiant energy exchange through participating media composed of arbitrary concentrations of H₂O, CO₂, and CO

Gas emissivities and absorptivities for H₂O–CO₂–CO mixtures