A master's thesis in the College of Engineering at the University of Basrah discussed (an experimental and numerical study of the effects of cracks and holes on the natural convection from the fin system in a horizontal and vertical heat sink) The thesis presented by the student Al-Mustafa Abdel-Karim dealt with the study of heat transfer from rectangular fin arrays by natural convection experimentally and numerically in horizontal, vertical and inclined cases for a variety of heating inputs. In the experimental study, five shapes of fins were made by making incisions and holes for the rigid fin assembly. For the notched fin experiments, the depth of these notches was increased in three levels. The combined effect was also studied For cracks and holes on the natural convection properties. A series of experiments were conducted on all current fin shapes to study the effect of longitudinal inclination from the vertical position on heat transfer by natural convection. In the numerical study, a heat sink with rigid rectangular fin arrays has been simulated in a horizontal and vertical model using CFD simulations. In both simulations, the effect of natural convection was investigated by changing the heat flux through the heat sink. Results were presented using streamlines, temperature lines, heat transfer coefficient values, and Nusselt number values The objective of the thesis is an experimental and numerical study of the effects of cracks and holes on the natural convection from the fin system in a horizontal and vertical heat sink. The thesis concludes that the heat transfer coefficient increases with increasing heat flow rates for both simulations. Also, the vertical case simulation indicates an average heat transfer coefficient and Nusselt number higher than the horizontal case simulation by 4% at all levels of heat flow.