Condensation characteristics of high pressure steam with non-condensable in a heat exchange tube of passive auxiliary feedwater system in APR+

Abstract

A Single-tube COndensation exPeriment(SCOP) was performed to simulate the condensation phenomena of Passive Auxiliary Feedwater System (PAFS), which is introduced in Advanced Power Reactor Plus (APR+). SCOP tests were conducted for two pipes of different diameters (26.6mm, and 44.8mm of inside diameter) with 8.2m length and 2~4 degrees of the inclined angles of the upper and lower section of each tube. The experiments were performed at 1.5MPa~7.0MPa of steam pressure and 0.12kg/sec~0.45 kg/sec of steam flow. Also, the non-condensable gas effect was evaluated at low mass fraction as 1% which is the reliable maximum non-condensable gas concentration in the accident conditions of PAFS. As a result of the experiment, the local heat transfer coefficients of 26.6mm ID tube are average 24% higher than those of the 44.8mm ID tube. The tube thermal power of 26.6mm ID tube reaches around 62% of those of 44.8mm ID tube. Also, no slug flow was observed at every inclined angle as 2~4 degrees of SCOP experimental conditions. Based on the Kim and NO correlation, we developed a new turbulent condensation correlation for the turbulent region of the liquid film in the inclined horizontal and vertical tube. We introduced the factors to account for the different inclined angle effect and different diameter effect. Also, to calculate non-condensable gas effect, a new empirical model is presented based on the experimental data with high pressure steam including 1% non-condensable gas. The present correlation of pure steam was compared with the Shah and RELAP5 condensation models using the SCOP data. The RMS errors of the present correlation, Shah model, and RELAP5 model are 17.41%, 57.88%, and 43.07%, respectively: The new empirical model with non-condensable gas is compared with mechanistic model (NIM) using SCOP data with non-condensable gas. The RMS errors of the present empirical model and NIM model are 16.38%, and 44.74%, respectively.