Session: 13-01: Computer Code V&V - I

Paper Number: 134783

134783 - Tube Plugging Induced Temperature Non-Uniformity in Once Through Steam Generator 

Abstract: 

Multi-layered helically coiled tube bundles are used as heat-transfer area of High-temperature gas-cooled reactor-Pebble Module (HTR-PM) Once Through Steam Generators (OTSGs). Tube plugging is very common in Pressurized Water Reactor (PWR) steam generators. Though the corrosion in HTGR OTSG is not so severe as that in PWR SG, it has large possibility to plug tube. However, plugged tubes will lead to temperature non-uniformity in the shell side helium of the steam generator. Large temperature non-uniformity will raise the tube working temperature. Excessive temperature non-uniformity will also lead to high thermal stress of the tube sheet. Thus, a precise prediction of temperature distribution and non-uniformity after tube plugging is essential for the safety and efficiency of HTGR OTSG.

In current investigation, an in-house code for tube and shell side coupled thermal analysis of HTGR SG is developed based on porous media assumption. This code is used to simulate the tube and shell side temperature distributions after plugging 1 or 2 tubes. Numerical simulation shows that plugging one tube of inner layer will lead to more severe temperature non-uniformity than that of outer layers. The temperature non-uniformity will become obvious when the number of plugged tube increases. In porous media assumption, the effect of molecular diffusion, turbulent diffusion and the dispersion are all modeled using the effective thermal diffusivity, which is normalized as the Peclet number (Pe). However, the Pe number of cross flow over tube bundles varies in previous investigations. Thus, in the current investigation, a large range of Peclet number is used for simulation. When Pe increases, outlet steam temperature non-uniformity become more severe. The code is validated using experiments carried out on the Engineering Test Facility for Steam Generator (ETF-SG) of HTR-PM. Experiments were carried out for cases with 1 or 2 tubes plugged. Plugging 1 tube of the most inner layer will lead to an increase of outlet steam temperature about 10 ℃. Plugging 2 tubes of the most inner layer will lead to an increase of outlet steam temperature about 19 ℃. While plugging 1 tube of most outer layer will lead to an increase of outlet steam temperature about 8 ℃ and plugging 2 tubes of the most outer layer will lead to an increase of outlet steam temperature about 9 ℃. Comparison shows that the present code can predict the experimental measurements well. Both experimental and numerical results show that plugging tube in inner layer will induce larger temperature non-uniformity compared with that in outer layers.

Presenting Author: Yunhao Luo Insititude of Nuclear and New Energy Technology

Presenting Author Biography: Yunhao Luo received the B.S degree in Energy and power engineering from North China Electric Power University, in 2022. He is currently working straightly toward the Ph.D degree in Nuclear Science and Engineering with Institute of Nuclear and New Energy Technology, Tsinghua University, China. His reseach interests include mixing of cross flow over tube bundles, temperature uniformity in helical tube steam generator.

Authors:

Yunhao Luo Insititude of Nuclear and New Energy Technology
Xiaoyang Xie Institute of Nuclear and New Energy Technology
Xiaowei Li Institute of Nuclear and New Energy Technology
Xinxin Wu Institute of Nuclear and New Energy Technology