Abstract
The effect of different lower air inlet tube inclinations on the gas dynamics, including concentration, fluid flow profile, temperature, and heat transfer potency, to the bottom part of a rotary hearth furnace (RHF), were investigated. The lower air-inlet tube inclination was varied from 5° to 25° upwards with the horizontal to maximize the burner efficiency. The inlet tube configuration with the lower two air-inlet tubes inclined at 10° upwards emerged as the most efficient tube orientation in the present burner system. This air inlet configuration of the burner produced the maximum heat transfer efficiency in transferring the combustion heat produced in the freeboard region to the bottom pellet layer region. Moreover, it was also able to produce better CO post-combustion efficiency.
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Abbreviations
- \(C_{1\varepsilon } ,C_{2\varepsilon } ,C_{3\varepsilon } ,C_{\mu }\) :
-
Constants of standard k-ε model
- C P :
-
Specific heat at constant pressure, J/kg K
- C pm :
-
Average specific heat at constant pressure, J/kg K
- C k :
-
Concentration of gas component k (CO and CO2), moles/m3
- D k :
-
Diffusion coefficient for gas species k (CO and CO2), m2/s
- E :
-
Total energy per unit mass, J/kg
- E a :
-
Activation energy, J/mol
- G b :
-
Production of turbulent kinetic energy by buoyancy, J/m3s
- G k :
-
Production of turbulent kinetic energy by velocity gradient, J/m3s
- g j :
-
Component of gravitational vector in the jth direction, m/s2
- I :
-
Radiation intensity, W/m2 sr
- I b :
-
Black body radiation intensity, W/m2
- I bw :
-
Black body radiation at furnace temperature, W/m2
- I in :
-
Intensity of incoming ray, W/m2 sr
- K :
-
Equilibrium constant
- K eff :
-
Effective thermal conductivity of the pellet, W/m K
- k :
-
Turbulent kinetic energy, m2/s2
- \(k_{{Fe_{x} O_{y} }} ,k_{C}\) :
-
Rate constant which follows the Arrhenius law
- k o :
-
Pre-exponential constant, m2/s
- M :
-
Molecular weight, kg/mol
- \(\overrightarrow {n}\) :
-
Outward normal vector
- P :
-
Total pressure inside the pellet, atm
- \(P_{{CO,CO_{2} }}\) :
-
Partial pressure of CO and CO2.
- p :
-
Pressure, Pa
- Q :
-
Total heat of the reaction \(Q = \sum\limits_{i} {R_{i} \left( { - \Delta H_{i} } \right)}\) Ri represents the reaction rate for the species ‘i’ in mol/m3, and ΔH represents the heat of the ith reaction in J/mole
- R :
-
Universal gas constant, J/mol K
- r :
-
Distance of a point from the centre of the pellet, m
- \(\overrightarrow {r}\) :
-
Position vector, m
- S chem :
-
Source term of heat of chemical reaction, J/m3 s
- S k :
-
Source term of gas species k (CO and CO2) in species transport equation, J/m3 s
- S rad :
-
Source term for heat of radiation, J/m3 s
- Sc t :
-
Turbulent Schmidt number
- \(\overrightarrow {s}\) :
-
Unit direction vector, m
- T :
-
Pellet temperature, K
- T 0 :
-
Initial temperature of pellet, K
- t :
-
Time, s
- u i :
-
Velocity component, m/s
- Y i :
-
Mass fraction of species i
- Y P :
-
Mass fraction of any product species
- Y R :
-
Mass fraction of any reactant species
- \(\beta\) :
-
Coefficient of thermal expansion
- \(\delta_{ij}\) :
-
Kronecker delta
- \(\varepsilon\) :
-
Dissipation rate of turbulent kinetic energy per unit mass, m2/s3
- \(\varepsilon_{w}\) :
-
Wall emissivity
- K:
-
Absorption coefficient, 1/m
- \(\mu\) :
-
Molecular viscosity, kg/m s
- \(\mu_{eff}\) :
-
Effective viscosity, kg/m s
- \(\mu_{t}\) :
-
Turbulent viscosity, kg/m s
- \(v_{i,r}\) :
-
Stoichiometric coefficient for reactant i in reaction r
- \(v_{i,r}^{\prime\prime}\) :
-
Stoichiometric coefficient for product i in reaction r
- ρ :
-
Density, kg/m3
- σ :
-
Stefan-Boltzmann constant, W/m2 K4
- \(\sigma_{k}\) :
-
Turbulent Prandtl number for k in standard k-ε model
- \(\sigma_{\varepsilon }\) :
-
Turbulent Prandtl number for ε in standard k-ε model
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Sooraj, S., Mishra, S., Kumar, B. et al. Optimization of lower air inlet tube configuration for maximizing burner efficiency based on gas dynamics, and heat transfer potency in a Rotary Hearth Furnace. Sādhanā 48, 65 (2023). https://doi.org/10.1007/s12046-023-02095-2
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DOI: https://doi.org/10.1007/s12046-023-02095-2