Effects of sinusoidal turbulator in cylindrical channel on heat transfer and flow characteristics

Effects of heat transfer and flow characteristics on Reynolds numbers of different sinusoidal turbulators placed separately from a pipe in the turbulent flow were investigated experimentally. The experiments were carried out under forced flow and constant heat flow conditions. The elements, which drew a sine curve used as a turbulator, were positioned axially to the channel centre. The experiments were repeated for 3 width values of sinusoidal turbulators that correspond to 3D/4, D/2 and D/4 (D = inner diameter of test pipe). The experiments showed that although there were increases in the rate of heat transfer with the turbulator, they caused considerable pressure drop. As a result, as the width of the turbulator increased, the heat transfer ratio (the Nusselt number) and coefficient of friction increased. Increase in Nusselt number was about 39-86% at D/4 width, 70-119% at D/2 width and 72-170% at 3D/4 width. It was observed that the coefficient of friction was significantly affected by the width of the sinusoidal turbulator, being about 0.02 in the case of straight pipe, 0.184 - 0.242 at D/4 width, 0.345 - 0.415 at D/2 width, and 0.416 - 0.451 at 3D/4 width. In addition, increasing coefficient of friction increased pressure drop and power required for pumping.