Numerical Investigation of Pulsating Flow Structures and Heat Transfer Enhancement Performance in Spherical Corrugated Helical Tube

Spherical corrugated helical tube is a new type of enhanced heat transfer device. In this paper, square wave pulsating flow is applied to spherical corrugated helical tube. The flow structure and heat transfer enhancement characteristics are numerically investigated. The numerical results are in good agreement with the experimental results. The flow characteristic of the spherical corrugated section in a pulsating period is analyzed in detailed. The turbulent kinetic energy and Nusselt number under steady and pulsating flow conditions are further studied. The numerical results show that pulsating flow can improve the secondary flow field in the spherical corrugated section and increase the turbulent kinetic energy of fluid. The average values of local Nusselt number along the circumference of wall in the central cross section of spherical corrugation increase 38.5% at the maximum compared with those at the steady flow state. The paper has also explored the effect of pulsating parameters including dimensionless frequency Wo number and dimensionless amplitude ‾A on the thermal performance of spherical corrugated helical tube. Within the scope of research, the overall thermal performance increases first and then decreases with the increase of Wo, and decreases with the increase of ‾A. The best overall thermal performance increased 13% at De=2936, Wo=35, ‾A=0.5