Analysis on flow structure and improvement of heat transfer in 3D circular tube with varying axial groove turbulator configurations

摘要

Using passive devices are an efficient method to enhance streamline behavior when liquid flows through the circular pipe. The interrupted structure groove is usually used to change the flow patterns. In this analysis, a heat performance numerical technique is applied to study the characteristics of fluid flow and heat transfer of the circular pipe using different axial groove geometrical configurations with different axial groove numbers, including 2, 3, and 4, under different conditions. The number of annular grooves and circumferential positions are the important parameters to analyse with varying operating conditions, with the Reynolds number (Re) range from 1500 to 23,000. A three-dimensional coordinate pipe system is applied using tetrahedron grids. The discretization equations are obtained by deriving algebraic approximations to integral conservation equations. Results observed that using this type of passive method has a low effect on pressure dope compared to the normal one (smooth pipe). The flow change occurs near and closed to the axial groove parameters. Moreover, the Nusselt number (Nu) value for the groove turbulators was higher than the normal one, about 14.5%-21%. The friction factor (f) value for the groove turbulators was higher than the normal one, were about 7.5%-24%. Most friction losses are caused by dynamical pressure dissipation owing to more viscous losses closed to the wall surfaces. The improvement of heat performance using this type of passing method was more than 1.2%.