Investigations On Effects Of Rolling Motion On Characteristics Of Heat Transfer In Rectangular Narrow Channel

Experimental and theoretical investigations of boiling heat transfer characteristics in a vertical rectangular narrow channel under rolling motion are conducted. Annular flow model of rectangular narrow channel in rest condition is established and analyzed.A mechanical rolling thermal-hydraulic experimental facility is used to conduct the experiments. Deionized water is used as the working fluid. The forces acting on fluid under rolling motion condition are analyzed. The research shows that the amplitude of tangential additional inertial force is about 11 times that of the normal additional inertial force, the additional pressure drop caused by tangential additional inertial force is bigger than the pressure drop caused by normal additional inertial force. The percentage of the additional pressure drop to the total pressure drop in the boiling two-phase flow region is 0.64%, so the effect of the additional pressure drop in the boiling two-phase flow region can be ignored when calculate the total pressure drop. The experimental research on the fluctuation of the pressure drop, mass flow rate and wall temperature has been conducted. The experimental results show that the pressure drop of the test section fluctuates periodically due to the steam-water mixture blocking and dredging periodically in the connection of the test section and the condenser, the amplitude of pressure drop fluctuation increases with the increase of the angle or period of the rolling motion. The mass flow rate fluctuates resulting from the fluctuation of the pressure drop with the same period. The temperatures of water and wall also fluctuate and the amplitude of water temperature fluctuation is bigger than that of the wall temperature fluctuation. Water temperature fluctuation delays 2-3 s than pressure drop fluctuation; wall temperature fluctuation delays 1-1.6 s than water temperature fluctuation.For boiling heat transfer coefficient, its fluctuation amplitude increases with the increase of the angle or period of the rolling motion. Its value in rolling motion condition is equals to that in rest condition. Its fluctuation amplitude also increases with the increase of heat flux and mass flow rate or the decrease of system pressure. In rolling motion with short period, its curve is close to sine or cosine curve.Established mass conservation and momentum conservation of the annular flow model in rectangular narrow channel, then predicted the boiling heat transfer coefficient and pressure drop gradient of the test section, the result show that the predicted data falling within ± 30%error band and the mean absolute error is 19.6%. With the increase of the axial distance the annular flow film thickness decrease and the gradient of film thickness increase. The heat flux and the high of the rectangular narrow channel have a big influence on the annular flow film thickness. The speed distribution in the liquid film is not linear and the speed increase with the increase of heat flux or decrease of mass flow rate,high or width of rectangular narrow channel, the speed distribution in the liquid film is almost linear when the aspect ration reaches a certain value.