Experimental study for determining the mass transfer coefficient under two-phase flow boiling condition

• Author / Creator

  Shen, Chen

• The mass transfer is an important phenomenon associated with a wide range of problems in the nuclear industry, such as materials degradation of components and fouling of heat exchangers and steam generators. However, mass transfer under a two-phase flow boiling condition has not been successfully investigated using direct experimental approach due to experimental difficulties. To fulfill the knowledge gap in this area, the objective of this project is to develop a novel experimental device and measurement technique to investigate mass transfer rate under the flow boiling condition. Because of the challenges associated with research in this area, the current study has been divided into three phases: (I) a bulk boiling condition, (II) a pool boiling condition and (III) a two-phase flow boiling condition. In Phase I, a rotating cylinder electrode system was employed to mimic the flow condition, and the electrolyte was heated to obtain the bulk boiling condition. The mass transfer behavior of oxygen and ferricyanide were determined from room temperature to just below the boiling point (i.e. 99 C) for rotating speeds between 100 and 3300 rpm. A correlation was successfully developed to predict the mass transfer behavior for the dissolved oxygen reduction and ferricyanide reaction below the boiling condition. However, the experimental data obtained under bulk boiling conditions was on the average 38% higher than the predicted data due to the generation and rupture of boiling bubbles in the bulk solution. In Phase II, a novel pool boiling setup was designed and constructed to study the mass transfer behavior on a nucleate boiling surface at atmospheric pressure. This study made a valuable contribution to the existing knowledge of mass transfer study on nucleate boiling surface because it is the first successfully attempt according to the open literature. Potassium ferricyanide and hydrogen peroxide were used as the non-volatile and volatile reaction species, respectively. It was found that under subcooled nucleate boiling and fully developed nucleate boiling conditions, the mass transfer coefficient increases with the increasing electrolyte temperature and heat flux for both species. The increase for hydrogen peroxide was faster than that for potassium ferricyanide due to the transfer of hydrogen peroxide ions through both the liquid and vapor phases during the reaction. In addition, an empirical correlation was proposed to include the bubble induced micro-mixing and macro-mixing effects, which occurred during boiling and was proven to agree well with our experimental data. In Phase III, a novel high temperature and pressure experimental flow loop and measuring technique were developed to determine the mass transfer rate under the flow boiling condition. The experimental setup and measuring technique enabled us to study the mass transfer behavior under the flow boiling condition to a level that no one else has been achieved according to open literature. The mass transfer coefficients were determined experimentally for the first time using this flow loop. An empirical correlation was proposed to represents our experimental data within 10% error. This work will provide a good base for further flow boiling mass transfer studies.

• Subjects / Keywords

  • Mass transfer
  • Limiting current
  • Flow boiling
  • Electrochemical method

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3XK84Z48

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.