Effects of sinusoidal strip element with different amplitudes on heat transfer and flow characteristics of circular channels

In this study, the effect of Reynolds number in turbulent flow on heat transfer and flow characteristics for different sinusoidal decoupled strip elements placed separately from the pipe was investigated experimentally. Experiments were carried out under forced convection and constant heat flux conditions. Corrugated strip elements were positioned axially at the pipe center, which draws a sinusoid used as a turbulator. Experiments were repeated for three different amplitudes of sinusoidal strip elements with 3D/4 width, D/8, 3D/16, and D/4. Experiments showed that although the strip elements enhanced heat transfer at different rates, they also caused a considerable pressure drop. As a result, it was seen that the heat transfer ratio, i.e., the Nusselt number, increased with the amplitude value. This ratio is 47% to 80% at the D/8 amplitude, 44% to 100% at the 3D/16 amplitude, and 75% to 174% at the D/4 amplitude in a straight pipe. It was determined that the friction coefficient is significantly affected by a sinusoidal corrugated strip element. It was determined that the value of friction coefficient is around 0.02 in a smooth pipe, 0.17 to 0.25 at n = D/8, 0.35 to 0.42 at n = 3D/16, and 0.43 to 0.45 at n = D/4 .