Heat transfer and pressure drop characteristics an array of rectangular modules inside a rectangular duct were experimentally studied using air as the working fluid. The research was conducted with the aim of simulating the cooling of eletronic components by forced convection. Mass ( Heat ) transfer coefficients were determined via naphthalene sublimation technique for three different situations, namely (a) for modules in the basic array, composed of regular modules only, (b) for a tall module positioned at all positions in the array center longitudinal row, and (c) for the modules in the neighborhood of the tall module. With basis on the results obtained, relations for the Sherwood (Nusselt) Number were obtained as a function of the Reynolds Number, which varied from 2000 to 7000. The Sherwood Number for the tall module was found to be higher than the one for the regular module at the same position. This increase was of the order of 90-95 percent, in the fully developed region and for low Reynolds Number. It was found that the presence tall module caused of the significant enhancements on the heat (mass) transfer coefficient of the neighboring modules, reaching in same cases 50 percent increases. The regular modules situated by the sides of the tall module underwent the highest enhancements on heat transfer. Pressure Measurements on the array with and without the tnll module where performed. In the presence of the tall module, an additional pressure loss was observed, being equivalent to the loss associated with approximately six transversal rows of regular modules, for the lower Reynolds Number.