Experimental study on condensation heat transfer characteristics in C-shaped tube under rolling conditions

Abstract

C-shaped tube heat exchanger has the advantages of good performance in heat transfer, space-saving, and reliability, and thus it has great potential to be used as passive residual heat removal heat exchanger in offshore nuclear power plants. In the present study, the condensation heat transfer characteristics in a C-shaped tube, which is the basic unit of C-shaped tube heat exchanger, were investigated experimentally, and the experiment was carried out under steady state and rolling conditions respectively. The effect of heat flux and rolling conditions on the condensation heat transfer characteristics were studied. The heat flux varies from 73.3 kW/m2 to 446.7 kW/m2; the rolling amplitude varies from 5° to 15°; and the rolling period ranges from 5 s to 20 s. The experimental results show that the condensation in the C-shaped tube is gravity-dominated. Based on the experiment data, a new correlation used to calculate the heat transfer coefficient of a C-shaped tube under steady state has been obtained. The rolling motion has significant effect on the condensation heat transfer of the C-shaped tube. With the increase of rolling angle from 0° to 15°, the condensation heat transfer performance of the C-shaped tube gradually increases and the increase rate of the condensation heat transfer coefficient is up to 18%. On the other hand, with the increase of rolling period from 5 s to 20 s, the condensation heat transfer performance of the C-shaped tube decreases. Further investigation revealed that, as the heat flux increases, the effect of rolling motion on the condensation heat transfer decreases.