Study On Flow Resistance Under Natural Circulation

Experimental study and theoretical analysis on the flow resistance of the natural circulation for single-phase water under rolling condition and non-rolling is carried out.The natural circulation and forced circulation experiments are performed by using water as the working fluid. The test section is a vertical stainless steel tube. Under non-rolling and rolling conditions, mechanism analysis on friction characterizes of natural circulation and velocity distributions within the working fluid are carried out. The reason for the loss of heating power and analysis of compensation of pressure under rolling condition are explained.Rolling conditions and non-rolling conditions of forced circulation flow resistance characteristics of experimental and the test of natural circulation flow resistance characteristics are carried. According to data analysis, the difference of friction characteristics between natural circulation and forced circulation and mechanism of resistance characteristics of the process of increasing power and reducing power under the condition of the natural circulation are obtained. At the same time, the changes of friction characteristics of different rolling angle and period are studied.The typical experimental phenomena in the experiments are described. Average method is used to processe experimental data. According to the processed experimental data, the semi-empirical correlations of friction characteristics of natural circulation under non-rolling condition is fitted out and analysis the friction characteristics of natural circulation under rolling condition of different average flow flux, different rolling angles, different rolling period.The experimental results shows that, under natural circulation condition of non-rolling, there is difference between increased power and reduced power in the process of heating, Less power resistance characteristics during the test section with a lag. Under the rolling state of natural circulation, Increasing the rolling cycle and increasing the rolling angle has the same effect which increase the severity of experimental tube swing, causes friction coefficient of test section increase compared with the steady-state and flow flux decrease.