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Abstract
The influence of air speed, spray density and tube bundle on wet air cooling of the fins are analyzed through numerical solution. The spray water droplets are released from the surface injection source in the discrete phase model (DPM). And the water film is formed in three-dimensional fins using Eulerian wall film model (EWF). The species transport model is coupled with EWF model to solve the phase transition and heat exchange. The heat exchange and pressure loss of tube bundle are evaluated through field synergy principle and Fanning friction factor, and a comprehensive performance factor is obtained. Based on the fins with outer diameter of 57 mm, 50 mm and 42 mm, the comprehensive factor
and mass transfer coefficient of 57 mm fins are higher than that of other two fins under varied air flow rate and spray density. Besides, The increase in tube rows number weakens the mass exchange of unit area. When the Re exceeds 2,820, the comprehensive performance of finned tube bundle with more rows become worse.
| Nomenclature | ||
| = | surface area (m−2) | |
| = | phase change constant | |
| = | drag coefficient | |
| = | specific heat (kJ·kg−1·K−1) | |
| = | diameter (m) | |
| = | mass diffusivity coefficient (m·s−2) | |
| = | force (N) | |
| = | gravitational acceleration (m·s−2) | |
| = | narrowest air unit flow (kg·m−2·s−1) | |
| = | heat exchange coefficient (W·m−2·K−1 ) | |
| = | mass exchange coefficient (kg·m−2·s−1) | |
| = | latent heat (kJ·kg−1) | |
| = | enthalpy (kJ·kg−1) | |
| = | thermal conducivity (W·m−1·K−1) | |
| = | Lewis factor | |
| = | mass flow rate (kg·s−1) | |
| = | molar weight (kg·kmol−1) | |
| = | Nusselt number | |
| = | pressure (Pa) | |
| = | Prandtl number | |
| = | stress tensor (Pa) | |
| = | momentum (kg·m·s−1) | |
| = | energy source from air (J) | |
| = | heat flow at boundary layer (W·m−2·s−1) | |
| = | heat exchange (W) | |
| = | temperature (K) | |
| = | velocity (m·s−1) | |
| = | water mass fraction in air (kgw·kga−1) | |
| = | droplet distortion coefficient | |
| = | the ratio of narrowest flow surface to the upwind surface | |
| = | thickness (m) | |
| = | viscosity (kg·m−1·s−1) | |
| = | distance from cell to wall (m) | |
| = | density (kg·m−3) | |
| = | surface tension (kg·m−1) | |
| a | = | air |
| con | = | condensation |
| D | = | drag |
| f | = | fluid |
| fgwo | = | evaporation at 0 °C |
| i | = | inlet |
| l | = | liquid film |
| ma | = | unit quality air |
| masw | = | saturated air at water film temperature |
| Mix | = | mixture |
| o | = | outlet |
| p | = | particle |
| s | = | source |
| sat | = | saturation |
| v | = | vapor |
| vap | = | evaporation |
| w | = | water |
| = | tangential | |
| Nomenclature | ||
| = | surface area (m−2) | |
| = | phase change constant | |
| = | drag coefficient | |
| = | specific heat (kJ·kg−1·K−1) | |
| = | diameter (m) | |
| = | mass diffusivity coefficient (m·s−2) | |
| = | force (N) | |
| = | gravitational acceleration (m·s−2) | |
| = | narrowest air unit flow (kg·m−2·s−1) | |
| = | heat exchange coefficient (W·m−2·K−1 ) | |
| = | mass exchange coefficient (kg·m−2·s−1) | |
| = | latent heat (kJ·kg−1) | |
| = | enthalpy (kJ·kg−1) | |
| = | thermal conducivity (W·m−1·K−1) | |
| = | Lewis factor | |
| = | mass flow rate (kg·s−1) | |
| = | molar weight (kg·kmol−1) | |
| = | Nusselt number | |
| = | pressure (Pa) | |
| = | Prandtl number | |
| = | stress tensor (Pa) | |
| = | momentum (kg·m·s−1) | |
| = | energy source from air (J) | |
| = | heat flow at boundary layer (W·m−2·s−1) | |
| = | heat exchange (W) | |
| = | temperature (K) | |
| = | velocity (m·s−1) | |
| = | water mass fraction in air (kgw·kga−1) | |
| = | droplet distortion coefficient | |
| = | the ratio of narrowest flow surface to the upwind surface | |
| = | thickness (m) | |
| = | viscosity (kg·m−1·s−1) | |
| = | distance from cell to wall (m) | |
| = | density (kg·m−3) | |
| = | surface tension (kg·m−1) | |
| a | = | air |
| con | = | condensation |
| D | = | drag |
| f | = | fluid |
| fgwo | = | evaporation at 0 °C |
| i | = | inlet |
| l | = | liquid film |
| ma | = | unit quality air |
| masw | = | saturated air at water film temperature |
| Mix | = | mixture |
| o | = | outlet |
| p | = | particle |
| s | = | source |
| sat | = | saturation |
| v | = | vapor |
| vap | = | evaporation |
| w | = | water |
| = | tangential | |