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ABSTRACT
In this paper, numerical analysis of the pool boiling heat transfer on isothermal elliptical tubes with different aspect ratios at saturated condition is presented. Bubbles’ tip velocities and positions, interfacial topological changes as well as convection heat fluxes of five different cases are presented for wide ranges of wall temperatures. Both time-averaged and dynamic behaviors of flow physics and heat transfer are investigated. The departure time of the first bubble, its time-dependent and averaged velocities, and heat fluxes are obtained. Finally, a novel correlation is presented for the Nusselt number that accounts for the elliptical tubes’ diameter and aspect ratio.
Nomenclature
| 1′ | = | diameter in inches |
| Ar | = | Archimedes number |
| B | = | vertical diameter of elliptic |
| C | = | horizontal diameter of elliptic |
| Co | = | constant coefficient |
| Cp | = | specific heat at constant pressure |
| D | = | diameter |
| E | = | energy |
| = | volumetric forces at the interface | |
| g | = | gravitational acceleration |
| h | = | convection heat transfer coefficient |
| hfg | = | latent heat |
| h′fg | = | latent heat plus sensible heat |
| K | = | reverse of Jacob number |
| k | = | thermal conductivity |
| M | = | mass source term |
| N | = | Newton |
| Nu | = | Nusselt number, hD/kg |
| p | = | pressure |
| Pr | = | Prandtl number, µcp/k |
| q | = | heat flux |
| = | average heat flux | |
| Sp′ | = | modified dimensionless superheating |
| T | = | temperature |
| t | = | time |
| U | = | velocity |
| = | velocity transpose vector | |
| W | = | Watt |
| x | = | Cartesian coordinates component |
| y | = | Cartesian coordinates component |
| α | = | volume fraction |
| κ | = | curvature |
| µ | = | dynamic viscosity |
| v | = | kinematic viscosity |
| ρ | = | density |
| σ | = | surface tension |
| Subscripts | = | |
| f | = | final |
| i | = | initial |
| l | = | liquid |
| s | = | surface |
| sat | = | saturated |
| sup | = | superheated |
| t | = | total |
| v | = | vapor |
Nomenclature
| 1′ | = | diameter in inches |
| Ar | = | Archimedes number |
| B | = | vertical diameter of elliptic |
| C | = | horizontal diameter of elliptic |
| Co | = | constant coefficient |
| Cp | = | specific heat at constant pressure |
| D | = | diameter |
| E | = | energy |
| = | volumetric forces at the interface | |
| g | = | gravitational acceleration |
| h | = | convection heat transfer coefficient |
| hfg | = | latent heat |
| h′fg | = | latent heat plus sensible heat |
| K | = | reverse of Jacob number |
| k | = | thermal conductivity |
| M | = | mass source term |
| N | = | Newton |
| Nu | = | Nusselt number, hD/kg |
| p | = | pressure |
| Pr | = | Prandtl number, µcp/k |
| q | = | heat flux |
| = | average heat flux | |
| Sp′ | = | modified dimensionless superheating |
| T | = | temperature |
| t | = | time |
| U | = | velocity |
| = | velocity transpose vector | |
| W | = | Watt |
| x | = | Cartesian coordinates component |
| y | = | Cartesian coordinates component |
| α | = | volume fraction |
| κ | = | curvature |
| µ | = | dynamic viscosity |
| v | = | kinematic viscosity |
| ρ | = | density |
| σ | = | surface tension |
| Subscripts | = | |
| f | = | final |
| i | = | initial |
| l | = | liquid |
| s | = | surface |
| sat | = | saturated |
| sup | = | superheated |
| t | = | total |
| v | = | vapor |