The behaviour of an air-water mixed solar collector is simultated using meteorological data for Perpignan (France) and one region of Brazil close to the equator. The absorber surface of the collector constitutes a toothed profile. The water streams in open channels while the air flows in the ducts composed by the insulation and the absorber plate. Two cases were considered: the case in which the water and the air move in the same direction and the one in which the fluids move in opposite directions. The temperature distributions of the different components of the collector are calculated by using an implicit finite-differences method. A computer program was developed to evaluate the thermal performances of the collector as a function of various design parameters and water and air flow rates.