The objective of the present study is to investigate experimentally the effect of film evaporation on mixed convective heat and mass transfer in a vertical rectangular channel. Two parallel channel walls are wetted by a water film and heated by a constant heat flux, while the other walls are dry and thermally insulated. The liquid film temperature, the evaporated flow rate, the upward airflow temperature and humidity are measured. Wide ranges of inlet airflow velocity, heat flux and liquid film flow rate are considered. Cases of laminar and turbulent airflow are considered. The experimental results show that evaporation takes place on the majority of the surface of the two walls and, in some cases, evaporative cooling occurs especially for small heating flux and large air velocities. Moreover, a numerical study is carried out in the case of a laminar flow and its results are compared to experimental ones. These comparisons lead to a good agreement with respect to liquid film and airflow temperatures in addition to the evaporated flow rate.