Experiments were performed to investigate the heat transfer and fluid flow characteristics of arrays of heat-generating, block-like modules affixed to one wall of a parallel-plate channel and cooled by forced convection airflow. Heat transfer enhancements exceeding a factor of two were achieved by the use of multiple fence-like barriers, with the interbarrier spacing and the barrier height being varied parametrically along with the Reynolds number. The barrier-related pressure drop for a multi-barrier system was found-to be less than the corresponding multiple of the pressure drop for a single-barrier system when the interbarrier spacing is small. When the barriers are separated by six or more rows of modules, the direct multiple is applicable. The heat transfer coefficients at individual surfaces of the various modules were measured in fully populated arrays without barriers, in arrays with barriers, and in arrays in which there was a missing module. Perspectives on the heat transfer and pressure drop results were provided by flow visualizations performed using the oillampblack technique.