Buoyancy-driven convective heat transfer from a semi-circular cylinder for various confinements has been studied using numerical simulations for wide ranges of parameters, Reynolds numbers (1 ≤ Re ≤ 50), Richardson numbers (0 ≤ Ri ≤ 2), Prandtl numbers (0.7 ≤ Pr ≤ 50) and confinement ratios (0.2 ≤ β ≤ 0.8). A hot semi-circular cylinder is symmetrically kept in a 2D rectangular confinement. The circular side of the cylinder faces the upstream flow and the fluid flows against gravity in the channel. The governing equations are numerically solved using FLUENT and the results obtained are presented in the form of isotherms, streamlines, pressure coefficients, drag coefficients, Nusselt numbers, etc. The highest value of pressure coefficient increases with blockage ratio for all cases. The drag coefficient decreases with Re and shows complex phenomena with change in Ri and blockage ratio of the channel. Pressure drag has contributed more as compared with viscous drag in all cases. The curved surface showed more heat transfer than the flat surface of the semi-circular cylinder. The value of β also has great influence at large value of Peclect numbers (= 2500). Overall average heat transfer in terms of average Nusselt number is a function of Ri, Re, Pr and β.