Kinetic Energy Of Secondary Flow Research Articles

Mixed convective flow and heat transfer of supercritical CO2 in circular tubes at various inclination angles

We performed the numerical simulations of laminar mixed convective flow and heat transfer in a 0.5mm diameter and 1000.0mm length tube. The supercritical carbon dioxide in the tube was cooled at constant wall temperature. The inclination angles were in the range of −90° (vertical downward flow) to 90° (vertical upward flow). The velocity and temperature distributions, secondary flow, friction factor and heat transfer coefficient were plotted vs. inclination angles and gravity force magnitudes. The kinetic energy of secondary flow was introduced to quantify its effect on the heat transfer. It is found that under the mixed convective flow and heat transfer conditions, the horizontal flow display the largest heat transfer coefficients. The inclined flows at α=−30° and 30° also behave better heat transfer performance among various inclination angles. The effect of inclined angles on the heat transfer is decreased with decreases in the gravity force magnitudes. The combined parameter of Gr/Reb2 was used to quantify the buoyancy force effect on the flow and heat transfer.

Development of laminar mixed convection in a horizontal square channel with heated side walls

A finite element code is used for detailed analysis of mixed-convection flow in a horizontal channel heated from the side walls. The Reynolds number typically is Re=500, and the Grashof number varies around Gr=105. Firstly, the numerical code is validated by a quantitative comparison with results of particle-tracking experiments for the velocity and liquid crystal measurements for the temperature. It is concluded that the agreement between the numerical and experimental data is satisfactory and that the finite element approximation employed can be used in analyzing mixed-convection flow problems in complex geometries. Secondly, the velocity and temperature fields are further described by means of isovelocity and isotemperature lines. The results are quantified by the relative kinetic energy of secondary flow, the Fanning friction factor, and the Nusselt number as a function of the streamwise position. It seems that the resulting secondary flow induced by buoyancy forces causes a substantial increase in heat transfer, knowledge of which is of importance for the design of compact heat exchangers.

Study on secondary flows in annulus wall cascades (On secondary flow in annulus-wall boundary layers for stationary cascades)

The velocity profiles in annulus wall boundary layers, the outlet flow angles, the outlet flow velocities and the total pressure drop through annular cascades have been measured by removing the blade boundary layers, in order to clarify the effects of secondary flow in the annulus wall boundary layers. The numerical solutions of velocity profiles in the anulus wall boundary layers agreed with the experimental data. The effects of displacement thickness, deflection and chord length on the kinetic energy of secondary flow are discussed.

An approximate solution for kinetic energy of secondary flow in blade cascades

The effect of the velocity distribution at the inlet to blade cascades on the kinetic energy of secondary flows is treated on the basis of a simple mathematical model of an ideal fluid flow. The kinetic energy of secondary flow in reaction turbine blades is found to be very small, compared with that in impulse and compressor blades. The influence of blade spacing is also considered. By comparison with experimental data and with practical experience, the present results demonstrate the importance of separation of the three-dimensional, viscous fluid flow in blade cascades of finite length.