"ASSESSMENT OF ANNULAR FLOW BOILING IN THE CONTEXT OF COMPUTATIONAL FLU" by HRISHIKESH PRASAD RANGA PRASAD

Date of Award

2017

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Mechanical Engineering (MS)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Amitabh Narain

Committee Member 1

Kazuya Tajiri

Committee Member 2

Sunil Mehendale

Abstract

The main objective of the current work is to achieve a better understanding – through modeling and simulation/programming activities – of annular flow-boiling and its applications based on a synthesis of Computational Fluid Dynamics (CFD) simulations, existing correlations, and experiments. A unique and rigorous 2-D CFD simulations technique was developed for annular flow-boiling to propose a correlation for convective component of Heat Transfer Coefficient (HTC) – defined here as flow-boiling in the absence of nucleation. To provide a context for the correlation structure of convective component of HTC, flow-physics details of annular flow-boiling and correlation structure (based on fundamental considerations) for HTC have also been discussed. Further, other existing correlations for Nusselt number, void-fraction, flow-regime transition, and pressure-drop have been used to develop a general but first order engineering estimates-methodology for design of annular flow-boilers and flow-condensers. The first order estimates-methodology, thus developed for annular flow-boiler operations, was used to: (i) make a priori estimates of flow predictions towards choosing suitable instrumentations for the design of a particular test-section and associated flow-loop needed for a new high heat-flux flow-boiling experiments involving water as a working fluid), and (ii) define a range of experimental operating conditions – for a low heat-flux test-section and flow-loop (involving FC-72 as working fluid) facility from which experimental data needed to be obtained to throw light on the flow-physics being modeled by the CFD code. Furthermore, preliminary results from a different low heat-flux experiments are briefly discussed here and then compared with rigorous CFD simulations to achieve better understanding of the flow-physics.

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