Experimental and Theoretical Study on CHF of a Ultra-Supercritical Circulating Fluidized Bed Boiler Water-Wall Tube at near-Critical Pressures  

作　　者：WANG Wenyu MA Zhan QING Hao NIE Chao YANG Haoyu BI Lingfeng YANG Dong PAN Wenxiao 

机构地区：[1]State Key Laboratory of Multiphase Flow in Power Engineering,Xi'an Jiaotong University,Xi'an 710049,China [2]Department of Mechanical Engineering,University of Wisconsin-Madison,1513 University Ave,Madison,WI 53706,USA

出　　处：《Journal of Thermal Science》2023年第1期166-182,共17页热科学学报（英文版）

基　　金：supported by the National Natural Science Foundation of China(No.52076172)。

摘　　要：The experimental and theoretical research on the critical heat flux(CHF)in a uniformly heated water-wall tube of the efficient ultra-supercritical circulating fluidized bed(USCFB)boiler has been conducted.In particular,the experimental pressure varies from 18 MPa to 21 MPa,which is from 0.814Pcr–0.95Pcr(Pcr:critical pressure).The mass flux varies from 310 kg·m^(–2)·s^(–1)to 550 kg·m^(–2)·s^(–1).The inlet sub-cooling temperatures vary from 5°C to 10°C.The material of the tube is 12Cr1MoVg.From experimental investigation,the near critical pressure CHF test data of water are obtained.We find that the CHF mainly occurs when the vapor qualities are less than 0.4,and it occurs earlier(at lower vapor quality)when the pressure is closer to 22.115 MPa or the mass flux is smaller.From the experimental data,a correlation function for the CHF is established via regression and machine learning.Correlations established via machine learning greatly improved the regression accuracy.To study the CHF phenomenon mechanically,a theoretical model is established based on the near-surface bubble crowding model describing the DNB-type CHF.In the development of the CHF model,the friction resistance coefficient is determined according to our test results.By comparison with different experimental results,the near-surface bubble crowding model is well suited to describe DNB-type CHF.The calculation results of the model can provide reference for the optimal design of the USCFB boiler.

关 键 词：circulating fluidized bed critical heat flux near-critical pressure bubble crowding machine learning 

分 类 号：TK229[动力工程及工程热物理—动力机械及工程]