Numerical study of the spatial distribution of heat transfer coefficient during horizontal-tube falling film evaporation

To study the spatial distribution of heat transfer coefficient (h) of seawater falling film outside the horizontal tube, a three-dimensional transient two-phase model considering evaporation was developed. The phase transition was simulated through the Tanasawa model. The detailed distribution of h along circumferential angle (θ) and dimensionless axial distance (L⁎) was discussed. The influence of spray density (Γ), salinity of seawater (S) and evaporation temperature (Teva) on h, average values of h along θ and L⁎ was investigated in detail under the conditions of 0.03 ≤ Γ ≤ 0.07 kg/(m·s), 0 ≤ S ≤ 100 g/kg and 313.15 ≤ Teva ≤ 343.15 K. The simulation results show that there is a trough-like distribution in the variation curve of h along L⁎ when θ ≤ 120°. Increasing both Γ and Teva can increases the value of h along θ and L⁎. As the liquid flow parameters change, the h at L⁎ = 0.5 is mainly affected by the change of intensity of the liquid collision. In the scope of calculations, changing Γ has the greatest impact on h, followed by the change in Teva, and changing S has the least impact.