VELOCITY PROFILE UNDER THE CONDITIONS OF NATURAL TURBULENT CONVECTION ACCORDING TO THE HEAT SEPARATING SURFACES OF THE INTERNAL REACTOR DEVICES

Abstract

As a result of the processing and analysis of experimental data on natural convection of coolants for various forms of heat-transfer surfaces of in-reactor structures, a relation for the velocity profile along the normal to the heat exchange surface under conditions of natural turbulent convection in the coolant flow was proposed. By the example of a vertical isothermal surface, it is shown that for different values of the longitudinal coordinate there is a characteristic point at which the longitudinal velocity reaches its maximum value (umax) at the corresponding value of the transverse coordinate (ymax). This point divides the fluid flow along the heat exchange surface into two zones: an internal one adjacent to the wall and an external one located beyond the maximum value of the velocity. Taking for the characteristic scale umax and ymax and presenting experimental data in dimensionless form u/umax = f(y/ymax), generalization of experimental data obtained. The results of processing the experimental data of various authors are well generalized by the dependences obtained in the work for the velocity profile in the inner and outer zones of the coolant flow. The velocity profile at the horizontal, downward-facing heat transfer surface is characterized by the same regularities as for the vertical surface: the velocity in the near-wall region increases, reaches a maximum and then decreases. The results of processing the measured velocity profile for a horizontal cylinder according to the method proposed in the work show agreement with the generalized data for a vertical isothermal surface. The data of experimental studies of the velocity field around an isothermally heated sphere with free convection in water are also well generalized by the dependences proposed in this work. The analysis of the experimental data on the velocity profiles for various forms of heat-transfer surfaces under conditions of natural turbulent convection, carried out by the authors, shows that the velocity profile proposed by the authors along the normal to the heat exchange surface has a universal character.