This study deals with the buoyancy induced flow and heat transfer in a parallel plate channel with a heat source array, which simulates an electronic package. The heat source array consists of four discrete protruding heat sources made of copper. The focus of this study is concentrated on the effect of heat source blockage ratio (b(r)) on recirculating flow and cooling performance of the system. Studies are conducted both for flush mounted or protruding heat source cases. Four different values of the blockage ratio of the protruding heat sources (b(r) = 0.125, 0.25, 0.375 and 0.5) are considered. The range of the modified Grashof number covers the values between 9.6 x 10(5) and 1.53 x 10(7). In the experiments, flow visualization and temperature measurements are conducted. Numerical studies are performed via ANSYS Fluent software. From the experimental results and numerical studies, it is found that buoyancy induced flow and cooling performance is significantly affected by the blockage ratio of the heat source array. (C) 2018 Elsevier Ltd. All rights reserved.