Nusselt Number for Laminar Flow in Entrance Zone of a Hot Tube

Solving many important industrial problems requires knowing the values of the heat transfer coefficient of passing of one or more fluid streams in different equipment, systems or pipes. In the present study, a numerical model has been developed to simulate compressible fluid flow at the inlet of a hot pipe with different angles to the horizon. In this zone, the hydrodynamic and thermal boundary layers of the fluid flow are developing. Due to the turbulence of the fluid flow due to the interaction of heat and fluid flow inside this tube, a three-dimensional turbulent model was used for this simulation. For this purpose, continuity and compressible Navier-Stokes equations, Reynolds stress model, and turbulent and compressible energy equation have been solved simultaneously. Then, using a set of numerical runs by the concepts of experimental design and optimization methods, a predictive formula for the Nusselt number for these flows has been obtained. Finally, the ability of this formula has been investigated using a set of laboratory data.