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ABSTRACT
A three-dimensional lattice Boltzmann model is presented to simulate the film-boiling phenomenon. Single- and multimode film boilings are investigated. The flow and temperature fields around the vapor phase are obtained for various Jakob numbers. Furthermore, the effects of Jakob number on the Nusselt number and vapor tip velocity are investigated. The results show that on increasing the Jakob number, the bubble tip velocity increases while the Nusselt number decreases. Furthermore, it is found that in multimode film boiling, the peak and trough values of the local Nusselt number happen at the bubble position and the gap valleys between adjacent bubbles, respectively.
Nomenclature
| C | = | liquid phase composition |
| c | = | lattice speed |
| cs | = | lattice speed of sound |
| E | = | bulk energy |
| e | = | discrete particle velocity |
| F | = | intermolecular force |
| f | = | density distribution function |
| g | = | momentum distribution function |
| Gr | = | Grashof number |
| H | = | height |
| h | = | composition distribution function |
| hfg | = | latent heat of vaporization |
| j | = | volume diffusive flow rate |
| Ja | = | Jakob number |
| K | = | thermal conductivity |
| k | = | gradient parameter |
| M | = | mobility factor |
| = | volumetric mass source term | |
| n | = | unit vector normal to the surface |
| Nu | = | Nusselt number |
| p | = | dynamic pressure |
| Pr | = | Prandtl number |
| q | = | mass flow rate per unit volume |
| s | = | temperature distribution function |
| T | = | temperature |
| t | = | time |
| u | = | volumetric flow-averaged velocity |
| w | = | weighting coefficients |
| α | = | thermal diffusion coefficient |
| Γ | = | gamma function ( |
| δ | = | delta function |
| η | = | specific heat ratio parameter |
| λ | = | wavelength |
| λ′ | = | characteristic length |
| μ | = | viscosity |
| v | = | kinematic viscosity |
| ρ | = | density |
| σ | = | surface tension |
| τ | = | nondimensional relaxation time |
| ψ | = | free energy |
| Subscripts | = | |
| 0 | = | reference |
| α | = | direction index |
| b | = | bulk |
| i | = | phase component |
| l | = | liquid phase |
| v | = | gas phase |
| s | = | surface |
| Superscripts | = | |
| ∼ | = | local |
| * | = | nondimensional |
| − | = | modified |
| eq | = | equilibrium |
| sat | = | saturated condition |
| w | = | wall |
Nomenclature
| C | = | liquid phase composition |
| c | = | lattice speed |
| cs | = | lattice speed of sound |
| E | = | bulk energy |
| e | = | discrete particle velocity |
| F | = | intermolecular force |
| f | = | density distribution function |
| g | = | momentum distribution function |
| Gr | = | Grashof number |
| H | = | height |
| h | = | composition distribution function |
| hfg | = | latent heat of vaporization |
| j | = | volume diffusive flow rate |
| Ja | = | Jakob number |
| K | = | thermal conductivity |
| k | = | gradient parameter |
| M | = | mobility factor |
| = | volumetric mass source term | |
| n | = | unit vector normal to the surface |
| Nu | = | Nusselt number |
| p | = | dynamic pressure |
| Pr | = | Prandtl number |
| q | = | mass flow rate per unit volume |
| s | = | temperature distribution function |
| T | = | temperature |
| t | = | time |
| u | = | volumetric flow-averaged velocity |
| w | = | weighting coefficients |
| α | = | thermal diffusion coefficient |
| Γ | = | gamma function ( |
| δ | = | delta function |
| η | = | specific heat ratio parameter |
| λ | = | wavelength |
| λ′ | = | characteristic length |
| μ | = | viscosity |
| v | = | kinematic viscosity |
| ρ | = | density |
| σ | = | surface tension |
| τ | = | nondimensional relaxation time |
| ψ | = | free energy |
| Subscripts | = | |
| 0 | = | reference |
| α | = | direction index |
| b | = | bulk |
| i | = | phase component |
| l | = | liquid phase |
| v | = | gas phase |
| s | = | surface |
| Superscripts | = | |
| ∼ | = | local |
| * | = | nondimensional |
| − | = | modified |
| eq | = | equilibrium |
| sat | = | saturated condition |
| w | = | wall |