Experimental investigation of the effects of heat transfer by natural convection and radiation of horizontal sinusoidal waved fins on flat plate surfaces

Today, fins are used to increase heat transfer in various heat exchangers in aviation, aircraft, and chemical production facilities, and in a wide range of areas such as cooling of electronic circuits. Fin design is very important in terms of more efficient use of energy and high-performance operation of machines and electronic devices. A lot of research has been done on fin design in the literature and is still being done. Researchers have been working on new designs lately. In this study, the effects of horizontal wavy sinusoidal fins on flat plate surfaces with constant height, three different periods (1, 2, and 3), and four different amplitude values (1 mm H/30, 2 mm H/15, 3 mm H/10, and 5 mm H/6) on natural convection and radiation heat transfer were investigated with a designed experimental setup. The experimental setup was designed and manufactured within the scope of the thesis study. Experiments were carried out at 8 different input powers (2.5 - 20 Watts) with a flat plate, rectangular cross-sectional, and 12 sinusoidal wavy fin plates facing up, sideways, and down (0˚, 90˚, 180˚). During the experiments, the transient plate base temperatures were measured, then the data were reduced by obtaining the stable regime temperature values with the data computer. In total, 327 separate experiments were completed in approximately 1100 hours. The view factor was also considered while calculating the heat transfer by radiation. In addition, all fins are covered with matte black anode so that the radiation emission rate can be accepted as 1 in the radiative heat transfer calculation. Nusselt number (Nu) was used as an indicator while examining the experimental data in terms of natural convection performance. According to the findings, it is seen that the addition of fins increases the Nu values compared to the flat plate. Among the other sinusoidal fins, it was determined that the 1-period 2 mm (H/15) amplitude sinusoidal fin had higher Nu values than the rectangular finned plate. However, it was observed that Nu values decreased as the amplitude increased in sinusoidal wavy fins. The reason for this phenomenon is that as the amplitude increases, it prevents the natural convection movement and therefore reduces the convective heat transfer. It was observed that the sinusoidal wavy fin with 1 period and 2 mm (H/15) amplitude had the highest Nu values for all orientations. According to this result, it has been observed that the 1-period 2 mm amplitude sinusoidal fin provides an increase in Nu values up to 32.65%, 18.62% and 29.80% at 0˚, 90˚, 180˚ positioning, respectively, compared to the rectangular fin. According to the findings, it was determined that the Nu values of the fin positioning effects were 0˚, 180˚ and 90˚, respectively, from the largest to the smallest. t is among the results obtained that horizontal (0˚) positioning is a more efficient orientation than vertical (90˚) positioning, while downward (180˚) positioning is the most inefficient positioning. It was observed that the rate of heat transfer by radiation increased as the period and amplitude increased. It was observed that the 3-period 5 mm (H/6) amplitude sinusoidal wavy fin had the highest radiation but the lowest Nu values. It has been determined that the radiation rate in the total heat transfer from all sinusoidal wavy fins varies between 37% and 61%.