Abstract

Applications boiling are found in heat sinks for electronics cooling, nuclear and fossil fuel powered steam generators, distillation columns, concentrated solar power systems, glass melting furnaces, desalination chambers, and heat and mass exchangers. In order to increase the performance and safety margins of these applications, there is a need to develop tools that predict the thermal and fluid behavior during bubble growth. The analysis of boiling has been addressed by computer simulations, which employ methods for approximating mass and heat transfer at the interface.

However, most simulations make assumptions that could adversely affect the prediction of the thermal and dynamic fluid behavior near the bubble-edge. These assumptions include: (i) computation of mass transfer with local temperature differences or with temperature gradients at cell-centers rather than with temperature gradients at the interface, (ii) modified discretization schemes at neighboring-cells or a transition region to account for the interface saturation temperature, and (iii) interface smearing or distribution of mass transfer into multiple cells around the interface to prevent interface deformations.

The present work proposes methods to perform a simulation of nucleate boiling. The proposed methods compute mass transfer with temperature gradients at the interface, account for the interface saturation temperature, and model a sharp interface (interface within one cell) with mass transfer only at interface-cells. The proposed methods lead to a more realistic representation of the heat and mass transfer at the interface. Results of the simulation are in excellent agreement with theory on planar interface evaporation and growth of spherical bubbles in superheated liquid. In addition, numerical bubble growth rates compare well with experimental data on single bubble nucleation over a heated surface. The simulation of nucleate boiling with water and a 6.2 K wall superheat reveals large heat transfer coefficients over a 200 um distance from the interface. In addition, analyses of the wall shear stress indicate an influence region of two-times the departure bubble diameter.

Library of Congress Subject Headings

Nucleate boiling--Mathematical models; Ebullition--Mathematical models; Heat--Transmission--Mathematical models; Mass transfer--Mathematical models

Publication Date

7-2018

Document Type

Dissertation

Student Type

Graduate

Degree Name

Microsystems Engineering (Ph.D.)

Department, Program, or Center

Microsystems Engineering (KGCOE)

Advisor

Satish G. Kandlikar

Advisor/Committee Member

Steven Day

Advisor/Committee Member

Kara L. Maki

Campus

RIT – Main Campus

Plan Codes

MCSE-PHD

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