Natural convection is a physical mechanism that is mostly benefited in cooling of electronics. Due to the variety of the geometrical and operational parameters, industrial and scientific studies are continuing for better performance. One of the focuses is on perforations of heat sink fins as a passive flow control technique. This work experimentally investigates a sinusoidal wavy fin heat sink after fins were perforated with two different hole diameters. Heat sink was heated by using an electrical resistance for six different heating powers. The temperature at the heater-heat sink interface was measured with the aid of four thermocouples. Transient and steady temperature values were measured and then recorded by means of a data-logger. The details of the experimental setup are given alongside of visuals. It is desired to state some assessment and evaluations about the experimental setup. Related literature studies are also summarized in the introduction section. Heat transfer, Rayleigh and Nusselt numbers were calculated and compared with each other and parameters by means of 2D plot graphics. The time for reaching steady state is changing between 1.5 to 2 hours. Average wall temperature changes linearly with heating power. Average wall temperature values are between 300 and 370 Kelvin. Nusselt number increases with increasing Rayleigh number as expected. While Rayleigh number changes between 500,000 to 5,000,000 Nusselt number approximately increases from 18 to 25. 3 mm perforations yield better results in terms of Nusselt numbers, which means better thermal convection. Surface temperature trends are similar according to power increments. Considering experimental uncertainty, general performances of the two heat sinks are found similar. Some remarks for the future work are given in conclusion section.The original article was published on 31 December 2018https://dergipark.org.tr/en/pub/ijeat/issue/42280/505116