Graduation Semester and Year

2015

Language

English

Document Type

Thesis

Degree Name

Master of Science in Mechanical Engineering

Department

Mechanical and Aerospace Engineering

First Advisor

Daejong Kim

Abstract

High performance heat transfer devices are critical components in hybrid power generation systems. The design of a Recuperator for 'waste heat recovery' is crucial for reducing the operating cost of a hybrid system. Plate-fin heat exchangers occupy a special position among high performance heat exchangers because of the compactness, efficiency and flexibility they offer. The performance of these heat exchange devices is typically very sensitive to fluid property variations, axial conduction and heat losses to environment. This thesis presents a numerical model of a plate fin heat exchanger in which fluid property variations including temperature driven changes in specific heat capacity, viscosity and heat transfer coefficients, and axial conduction effects are explicitly modeled. The objective is to predict fluid properties at outlet of the heat exchanger as accurately as possible, using a computationally less expensive procedure. Finite Volume Method is used for discretization of the domain. Momentum equation is modelled using flow admittance concept and energy transport across flow field is modeled using the Advection-Diffusion equation. The model solves for mass flow rate and temperatures of fluid streams and for temperatures of solid structure. The numerical model is validated against analytical solutions in the appropriate limits and then used to analyze performance of an example heat exchanger core under specific set of operating conditions prescribed by a Solid Oxide Fuel Cell-Gas Turbine hybrid system cycle, in order to demonstrate its utility. The resulting numerical model is simple to implement and computationally efficient, therefore it can be easily integrated into complex system models as a sub-routine and also can be used as a stand-alone solver for parallel-flow or counter-flow heat exchanger simulation.

Keywords

Plate-fin heat exchanger, Hybrid power generation systems, Thermal engineering, Computational fluid dynamics, Finite volume method, Advection-diffusion equation

Disciplines

Aerospace Engineering | Engineering | Mechanical Engineering

Comments

Degree granted by The University of Texas at Arlington

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