MODELLING PHASE CHANGE MATERIAL THERMAL STORAGE SYSTEMS

MODELLING PHASE CHANGE MATERIAL THERMAL STORAGE SYSTEMS

By

JOANNE M. BAILEY, B.A.Sc., P .Eng.

A Thesis

Submitted to the School of Graduate Studies

in Partial Fulfillment of the Requirements

for the Degree

Master of Applied Science

McMaster University

Hamilton, Ontario, Canada

Copyright by Joanne Bailey, January 2010

MASTER OF APPLIED SCIENCE (2010) (Mechanical Engineering)

McMASTER UNNERSITY Hamilton, Ontario, Canada

TITLE: Modelling Phase Change Material Thennal Storage Systems

AUTHOR: Joanne M. Bailey, B.A.Sc., P. Eng.

SUPERVISOR: Dr. J. S. Cotton

NUMBER OF PAGES: xiv, 157

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ABSTRACT

In order to increase the overall efficiency of energy use in a community, excess

thermal energy from inefficient processes can be stored and used for heating applications.

A one-dimensional analytical conduction model is therefore developed for sizing of phase

change material thermal energy storage systems. The model addresses rectangular

channels of phase change material separated by flow channels for the addition and

removal of thermal energy. The analytical model assumes a planar melt front and linear

temperature profiles throughout the thermal storage cell. Heat flux and interface

temperatures are calculated at various melt fractions based on a quasi-steady electrical

analogue analysis of the instant in question. Compensation is made for the sensible

energy change between melt fractions by adding this energy at the calculated heat flux.

A two dimensional, conduction only computational fluid dynamics model is used to

compare the response of the analytical model to changes in the input parameters and

shows good agreement. A test apparatus and a three dimensional computational fluid

dynamics model are also created and melt-time results compared to analytical model

predictions. These comparisons also show good agreement. Finally, a thermal storage

system is sized for a specific application, H2Green Energy Corporation's Distributed

Storage System, with sizing based on the heat load requirements of McMaster Innovation

Park during the winter months. Technical feasibility of this system is shown with

analysis also included on economic feasibility. It is determined that the analytical model

is sufficient for initial assessment of phase change material thermal energy storage

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systems where detailed geometry is unavailable. Recommendations are made for further

validation of the model and the development of a phase change material properties

database. Suggestions are also presented on additional sources of revenue for the

H2Green Distributed Storage System that will increase its economic feasibility.

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ACKNOWLEDGEMENTS

The author would like to acknowledge the financial contributions of the Ontario

Centres of Excellence, H2Green Energy Corporation, McMaster University Department

of Mechanical Engineering, NSERC and the Canadian Engineering Memorial Foundation

towards completion of this thesis.

The author would also like to thank Dan Wright for his assistance with data

acquisition and programming, Ron Lodewyks, J.P. Talon, Mark MacKenzie, Jim

McLaren and Joe Verhaeghe for their help with the fabrication of the experimental

apparatus, Dr. J.S. Cotton for his guidance and supervision over the course ofthis project

and Dr. H.S. Sadek for his continual support and advice.

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Table of Contents

Abstract .............................................................................................................................. iii

Acknowledgements ............................................................................................................. v

List of Tables ..................................................................................................................... ix

List of Figures ..................................................................................................................... x

Nomenclature .................................................................................................................... xii

Glossary ........................................................................................................................... xiii

CHAPTER 1 - Introduction ................................................................................................... 1

1.1 - Background ............................................................................................................ 1 1.2 - Current Applications of Thermal Storage ................................................... , .......... 2 1.3 - Potential Applications of Thermal Storage ............................................................ 5 1.4 - Problem .................................................................................................................. 7 1.5 - Scope of Work ....................................................................................................... 8

CHAPTER 2 - Thermal Storage Technologies ................................................................... 10

2.1 - Thermal Storage Options ..................................................................................... 10 2.2 - Phase Change Material Categories ...................................................................... 12 2.3 - Low Temperature Phase Change Materials ......................................................... 13 2.4 - Recent Phase Change Material Thermal Storage Research ................................. 19 2.5 - Capture Systems ................................................................................................... 24 2.6 - Recovery Systems ................................................................................................ 26 2.7 - Temperature Mediation Systems ......................................................................... 27 2.8 - Design Methodology ............................................................................................ 27

CHAPTER 3 ~ PCM Thermal Storage Models .................................................................... 32

3.1 - PCM Mass ............................................................................................................ 32 3.2 - One-Dimensional Storage Cell Geometric Model ............................................... 33 3.3 - Analytical Model Single Storage Cell Time ........................................................ 34

3.3.1 - Pseudo-Steady Heat Transfer Model ............................................................ 35 3.3.2 - Changing Temperature Profile and Sensible Energy .................................... 36 3.3.3 - Equations Used in the Analytical Model ...................................................... 37

3.4 - Fluent Melting/Solidification Model ................................................................... 38 3.5 - Two-Dimensional Numerical Storage Cell Model .............................................. 39

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3.5.1- Effect ofTheffilal Conductivity .................................................................... 44 3.5.2 - Effect of Latent Heat of Fusion ..................................................................... 49 3.5.3 - Effect of Sensible Energy Storage ................................................................ 50 3.5.4 - Effect of Capture/Recovery Temperature Difference ................................... 52 3.5.5 - Effect of Dimensional Changes .................................................................... 54 3.5.6 - Effect of Capture/Recovery Convective Heat Transfer Coefficient ............. 55

3.6 - Three-Dimensional Sample Cell Model .............................................................. 56 3.6.1 - Lauric Acid Storage Cell ............................................................................... 57

CHAPTER 4 - Test Facility ................................................................................................. 62

4.1 - Test Cell Design Criteria and Constraints ............................................................ 62 4.2 - Phase Change Material Chamber ......................................................................... 65 4.3 - Capture/Recovery Fluid ChanneL ........................................................................ 68 4.4 - Temperature Measurement .................................................................................. 73 4.5 - Flow Measurement and Control. .......................................................................... 75 4.6 - Heat Flux Measurement ....................................................................................... 76 4.7 - Data Acquisition .................................................................................................. 77 4.8 - Experimental Uncertainty .................................................................................... 79

CHAPTER 5 - Experimental Results, Discussion and Comparison .................................... 82

5.1 - Experimental Phase Change Results and Model Validation ................................ 82 5.2 - Lauric Acid Storage Cell Low Flow .................................................................... 83 5.3 - Effect of Flow Rate .............................................................................................. 89 5.4 - Effect of Flow Direction .......................................................................