Numerical study on falling film heat and mass transfer under counter-current airflow conditions

The sensible heat transfer of water (Qw), latent heat of water evaporation (Qr), sensible heat transfer of moist air (Qma), and the distribution of local wall convective heat transfer coefficient (h) in the process of the falling film evaporative cooling are quantitatively analyzed in this paper. The results indicate that water vapor partial pressure (Pv) and film Reynolds number (Rel) have a little influence on Qma and have a significant effect on Qw and Qr. The airflow velocity (Vma) and water inlet temperature (Til) strongly impact all heat transfer quantities. Qma has the smallest contribution to the overall heat, while the quantities of Qw and Qr depend on the influencing factors. At Rel of 250 and Til of 50 degrees C, when Vma >= 2 m/s, Qr predominates heat transfer but decreases slightly with Vma. When Vma reaches 1.5 m/s, Qr dominates the heat transfer atRel of 250 and Til of 60 degrees C. his highest at the liquid column sites and decreases in the axial and circumferential directions. h is improved by raising the Til, Rel, and Vma. However, h at some locations decreases when Vma exceeds 2 m/s. Moreover, h is slightly weakened by an increase in Pv.