Session: 07-07: Experiments and Analyses - VI

Paper Number: 138262

138262 - Experimental Study on the Liquid Film Behaviors of Annular Flow in the Rectangular Channel 

Abstract: 

In view of the advantages of large area ratio and strong heat exchange capacity, the narrow rectangular channel has been applied in energy and power industrial fields with limited space and high heat exchange requirements, such as the heat exchanger and the nuclear fuel assemblies. Critical heat flux (CHF) is the most important parameter related to the safety performance of heat exchanging equipment, whose triggering mechanisms are very complex and complicated. The prediction of dry-out critical heat flux in a narrow rectangular flow channel was usually based on the accurate prediction on the instantaneous liquid film spatial distribution and its characteristics in annular flow, such as liquid film thickness and disturbance wave destruction rate, and other key parameters. Therefore, it is essential to conduct detailed research on the liquid film behaviors for the annular flow in the narrow rectangular channel. At present, most researches focused on the liquid film in the gas-liquid flow at atmospheric pressure. However, the liquid film data were still scarce for the lack of the accurate and time-dependent measuring equipment.

 

In order to obtain the liquid film thickness, the plate-type liquid film sensor was developed by utilizing the huge differences of electrical conductivity between gas and liquid. The plate-type liquid film sensor consisted of two electrodes. One electrode was taken as the excitation electrode by inputting a 100 kHz sinusoidal AC stimulation signal, and the other electrode was used as the receiving one. The corresponding relationship between the measured voltage and the real void fraction was established with calibration of empirical model, and then the void fraction was converted into liquid film thickness theoretically. Based on the plate-type liquid film sensor, the liquid film was measured in the narrow rectangular channel with a cross-section of 4 mm × 66 mm at different flow conditions. The data of the liquid film thickness in the flow channel were acquired with the frequency of 10 kHz. The effects of liquid flow velocity and gas flow velocity on the averaged liquid film thickness and time fluctuation characteristics were analyzed. Moreover, the existing models for liquid film thickness in annular flow were evaluated, which presented the relative errors for the different models. This study provided data support and theoretical guidance for the accurate prediction of the dry-out type critical heat flux, and was helpful for the design of the fuel assemblies consisting of narrow rectangular channel and the safety assessment of nuclear reactor systems.

Presenting Author: Quan-Yao Ren NPIC

Presenting Author Biography: Major in thermal-hydraulics and fuel assembly design.

Authors:

Quan-Yao Ren NPIC
Zengping Pu NPIC
Qingche He Chongqing University
Hui He Shanghai Jiaotong University
Haidong Liu Chongqing University of Technology
Zhong Xiao NPIC
Liang-Ming Pan Chongqing University