Heat and flow characteristics were investigated numerically for a laminar stream past two tandem circular cylinders placed in a channel. The blockage ratios (beta = D/H) were chosen to be 0.6, 0.7, and 0.8, respectively, and the gap between the cylinders was varied proportionally to the cylinder diameter as g = 0.2D, 0.7D, 1.5D, and 4D at a low Reynolds number (Re = 40). The effects of the blockage ratio, as well as the gap between two cylinders on heat and flow features were examined in detail. Shear stresses, dimensionless static pressure, heat transfer coefficient, and separation points from the cylinders were determined from the velocity and temperature fields in the flow domain. The results showed that the separation angle decreases with both the blockage ratio and the gap size on the downstream cylinder, whereas heat transfer increases with both the blockage ratio and the gap size on the upstream cylinder.