Mass transfer characteristics of the high temperature falling film evaporation over a vertical wall under countercurrent laminar airflow

Abstract

The falling film evaporation with large heat fluxes often has high wall temperature. To investigate this evaporation mass transfer characteristics for the falling water film under countercurrent laminar airflow, those previous investigations about the water film flow to enhance heat transfer were carefully reviewed and these factors were expressed in an integrated form. Then, experimental studies were carried out. During data reduction, local data was used to obtain local Sherwood number and to reveal the characteristics of local Sherwood number along the flow direction. Results indicated that evaporation could be dramatically enhanced by the transient wavy interface and high advective mass transfer. Results also revealed that the evaporation by high temperature falling water film was obvious deviated from the laminar mass transfer. Finally, the experimental data was fitted to specify the expressed the correlation for evaporation mass transfer.