Modeling and simulation for a PEM fuel cell with catalyst layers in finite thickness

Jianghui Yin, Ryerson University

Date of Award

2007

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Mechanical Engineering

First Advisor

Jun Cao

Abstract

A detailed non-isothermal computational fluid dynamics (CFD) model for proton electrolyte membrane (PEM) fuel cells is developed in this thesis. This model consists of the equations of continuity, momentum, energy, species concentrations, and electric potentials in different regions of a PEM fuel cell. In particular, the fairly thin catalyst layers of the fuel cell are assigned a finite thickness instead of being treated as nil thickness interfaces in other PEM fuel cell models. Various source/sink terms are presented to associate the conservation equations with the electrochemical reaction kinetics. The water balance in the

membrane is modeled by coupling diffusion of water, pressure variation, and the electro-osmotic drag. The membrane swelling effect is explicitly considered the newly derived model, leading to a set of novel water and proton transport equations for a membrane under the partial hydration condition. The electron transport in the catalyst layers, gas diffusion layers and bipolar plates are also described. The PEM fuel cell model developed has been implemented into a commercial CFD software package for simulating various flow and transport phenomena arising in operational PEM fuel cells, analyzing the impact of design and operating parameters on the cell performance, and optimizing the PEM fuel cell design.

Use of concept maps and wikis for early engineering design and collaborative engineering

Janaka S. Weerasinghe, Ryerson University

Date of Award

2007

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Mechanical Engineering

First Advisor

Filippo A Salustri

Abstract

Concept Maps and wikis were examined as tools that compliment the engineering design process and better facilitate collaboration between geographically dispersed design teams. Concept maps are a visual knowledge capture medium that can be used to promote the understanding of the design problem and in providing an organizational reference for the entire project. Wikis are editable websites that give the users the freedom to add content in any manner, thus providing a project management platform for design teams. This thesis reports on five studies by the author in which concept maps and wikis are used as

both tools for the design process as well as collaborative tools in various modes of interaction. Recommendations to improve concept maps and wiki technologies were determined based on the feedback from the participants in these studies. The wiki was used extensively as a project management tool but required some push for the participants to use. The hierarchical layout structure has been shown to be the favoured pattern by participants in the engineering field. Concept maps are also shown to be a clearer visualization tool than another accepted tool, Unified Modelling Language.

Optimal control of a bleed air temperature regulation system

Lan Shang, Ryerson University

Date of Award

2007

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Mechanical Engineering

First Advisor

Guangjun Liu

Abstract

This thesis investigates temperature control of an aircraft engine bleed air system, aiming at reducing ram air usage to reduce fuel consumption while maintaining fast temperature control response. To achieve both of the objectives, a system configuration is designed to control both ram air and bypass flows. The analytical equations describing the systems dynamics are derived and utilized in developing the overall bleed air system model. Optimal state feedback control and output feedback control are applied in the

temperature control system. Computer simulations and experiments have been conducted, and the proposed configuration and control strategy are shown to be effective in minimizing ram air usage and

Optimal control of a bleed air temperature regulation system

Lan Shang, Ryerson University

Date of Award

2007

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Mechanical Engineering

First Advisor

Guangjun Liu

Abstract

This thesis investigates temperature control of an aircraft engine bleed air system, aiming at reducing ram air usage to reduce fuel consumption while maintaining fast temperature control response. To achieve both of the objectives, a system configuration is designed to control both ram air and bypass flows. The analytical equations describing the systems dynamics are derived and utilized in developing the overall bleed air system model. Optimal state feedback control and output feedback control are applied in the

temperature control system. Computer simulations and experiments have been conducted, and the proposed configuration and control strategy are shown to be effective in minimizing ram air usage and maintaining fast temperature control response in the meantime.

Thermo mechanical analysis of through-hole solder joint using strain partitioning method

Imtiaz Ahmed Shaik, Ryerson University

Date of Award

2007

Degree Type

Thesis Project

Degree Name

Master of Engineering (MEng)

Department

Mechanical Engineering

Abstract

Currently in the electronics industry there is a desire to increase component reliability. Fatigue failure in solder joints is an important design consideration for electronic packaging. In through-hole components, fatigue failure of leads has been observed to antecede fatigue failure of solder joints. The main objective of the study for a solder joint in a plated-through-hole bearing the pin during the temperature cycle was to ascertain the thermo mechanical behavior and the dominant deformation mode. The Digital Speckle Correlation (DSC) technique, which is a computer vision technique, was applied for the measurement of solder joint deforamtion for a prescribed outlined temperature and time. The dimensions for the area of the solder joint under study were 21 by 21 um, located at the centre of the hole. And computation of

averaged shear strains at 6 data points for this area was done. R Darveaux's constitutive model was applied for the data analysis such as the solder joint yields stress with respect to the time and temperature. On achieving the stress solution, the measured total strains were partitioned into elastic, plastic and creep terms separately and hence the creep strain was evaluated. From the analysis, it was found that the dominant deformation mode was shear deformation due to mismatch of coefficient of thermal expansion between pin and copper plating material of through-hole under thermal loading. And the dominant deformation mechanism was creep strain while stress started to relax at the end of ramp up and continued throughout the test and creep strain rate decreased during high temperature dwell. In Addition, the elastic strain was dominating during the initial stage of thermal cycle but later it was neglibible when compared to creep strain.

A numerical study of free convective heat transfer within domed skylight cavities

AmirAbbas Sartipi, Ryerson University

Date of Award

2007

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Mechanical Engineering

First Advisor

Abdelaziz (Aziz) Laouadi

Second Advisor

David Naylor

Abstract

Domed skylights are important architectural design elements to deliver daylight and solar heat into buildings and connect buildings' occupants to outdoors. To increase the energy efficiency of skylighted buildings, domed skylights employ a number of glazing layers forming enclosed spaces. The latter are subject to complex buoyancy-induced convection heat transfer. Currently, existing fenestration design computer tools and building energy simulation programs do not, however, cover such skylights to quantify their energy performance when installed in buildings.

his work presents a numerical study on natural laminar convection within concentric and vertically eccentric domed cavities. The edges of domed cavities are assumed adiabatic and the temperature of the interior and exterior surfaces are uniform and constant. The concentric and vertically eccentric domed cavities were studied when heated from inside and heated from outside, respectively. A commercial CFD package employing the control volume approach is used to solve the laminar convective heat transfer within the cavity.

The obtained results showed steady flow for small Grashof numbers. For moderate and large Grashof numbers, depending on the gap ratio and the cases of heating from inside or outside, the flow may be steady or transient periodic with a single vortex-cell or multi vortex-cells. The Nusselt number for the case of heated from inside is greater than the case of heated from outside. The numerical results show that the changes in the gap ratio have smaller effect on Nusselt number in high profile domed skylights than lower profile domed skylights.

A simplified model of the thermal interaction of a Venetian blind located on the indoor glazing surface of a window

Derek Roeleveld, Ryerson University

Date of Award

2007

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Mechanical Engineering

First Advisor

David Naylor

Abstract

A simplified model was developed to predict the radiative and convective heat transfer in complex fenestration systems, including the effect of solar radiation. The focus of the current work was on Venetian blinds mounted adjacent to the indoor window surface. From the perspective of convection, the model used a convective flat plate flow between the blind and ambient surroundings and a convective channel flow between the window and blinds. It was necessary to develop new empirical correlations to predict the average channel Nusslet numbers of the hot and cold walls separately.

Therefore, a CFG study of free convection in an asymmetrically heated channel was performed. Then, the new empirical correlations were used to develop a simplified one-dimensional model of the heat transfer in the system. The radiative heat exchange between the blind, window and room was calculated using a four surface grey-diffuse model. Sample predicted results were compared with existing experimental and numerical data from the literature.