WAVE POWERED DESALINATION Alan J. Crerar

309 Pages·2015·8.52 MB·English

WAVE POWERED DESALINATION
by
Alan J. Crerar
B.Sc. (Edinburgh)
Thesis presented for the Degree of Doctor of Philosophy
University of Edinburgh
November, 1989
To my family and to Anne.
"Learn to think."
W.G. Crerar, Architect.
The work described in this thesis is the original work of the author except
where specific reference is made to other sources. It has not been submitted,
in whole or in part, for any degree at any other University
iv
TABLE OF CONTENTS
UST OF FIGURES (cid:9) Viii
ACKNOWLEDGEMENT(cid:9) xii
ABSTRACT(cid:9) xiii
1 INTRODUCTION(cid:9) 1
1.1 OVERVIEW 2
1.1.1 Desalination 2
1.1.2 The Edinburgh Duck Wave Absorber 4
1.2 WAVE POWERED DESALINATION 6
1.2.1 Process Description 6
1.2.2 Auxiliary Equipment 7
1.3 PROJECT OVERVIEW 8
1.3.1 Research Programme 8
1.3.2 Scope of Thesis 10
2 LITERATURE REVIEW AND THEORY (cid:9) 17
2.1 DESALINATION 18
2.1.1 Overview 18
2.1.2 The MSF Process 21
2.13 Other Distillation Methods 24
2.1.4 Other Desalination Processes 30
2.1.5 Desalination Using Renewable Energy 36
2.1.6 Trends in Desalination 43
2.2 OCEAN WAVE ENERGY 45
2.2.1 Introduction 45
2.2.2 Linear Wave Theory 45
2.2.3 Wave-Device Interactions 51
2.2.4 The Wave Energy Resource 54
3 MODELLING AND SIMULATION OF THE DESALINATION PROCESS (cid:9) 68
3.1 INTRODUCTION (cid:9) 69
3.2 THE FIRST MODEL (cid:9) 69
3.2.1 Objectives (cid:9) 69
3.2.2 The Model Basis (cid:9) 70
3.2.3 Derivation of the Equations (cid:9) 73
3.2.4 Implementation of the First Model (cid:9) 77
3.3 THE SECOND MODEL (cid:9) 78
3.3.1 Objectives (cid:9) 78
3.3.2 The Model Basis (cid:9) 79
3.3.3 Derivation of the Equations (cid:9) 79
3.3.4 Implementation of the Second Model (cid:9) 92
3.4 SIMULATION OF EXPERIMENTAL APPARATUS (cid:9) 94
3.4.1 The First Model as a Design Tool (cid:9) 94
3.4.2 Modifications to the Second Model (cid:9) 95
4 DESIGN AND DEVELOPMENT OF THE EXPERIMENTAL FACILITY(cid:9) 101
4.1 INTRODUCTION 102
4.1.1 The Experimental Approach 102
4.1.2 Use of an Analogue Working Fluid 104
4.2 DETAILED DESIGN OF COMPONENTS 105
4.2.1 Design of Condenser/Evaporator Unit 105
4.2.2 Design of Liquid Cooler and Trim Heater 107
4.2.3 Design of the Compressor 109
4.3 INSTRUMENTATION AND CONTROL 114
4.3.1 Introduction 114
4.3.2 Piston Position Control 115
4.3.3 Data Logging and Process Control 121
5 RESULTS AND ANALYSIS (cid:9) 163
5.1 RESULTS FROM THE FIRST MODEL (cid:9) 164
5.1.1 Transient Performance Predictions (cid:9) 164
5.1.2 Performance Predictions (cid:9) 165
5.2 EXPERIMENTAL PROGRAMME (cid:9) 167
5.2.1 Procedure (cid:9) 167
5.2.2 Analysis of Experimental Data (cid:9) 170
5.3 RESULTS FROM THE SECOND MODEL (cid:9) 173
5.3.1 Transient Performance Predictions (cid:9) 173
5.3.2 Performance Predictions (cid:9) 174
5.4 SUMMARY (cid:9) 180
6 CONCLUSIONS AND RECOMMENDATIONS (cid:9) 225
7 APPENDICES (cid:9) 229
vi
I SEAWATER SCALE FORMATION AND CONTROL (cid:9) 230
1.1 Alkaline Scales (cid:9) 231
1.11 Calcium Sulphate Scaling (cid:9) 232
1.111 Methods of Scale Control (cid:9) 234
II ENHANCED HEAT TRANSFER IN FALLING FILMS (cid:9) 236
11.1 Condensation (cid:9) 236
11.11 Evaporation (cid:9) 238
III PROPOSALS FOR FUTURE WORK (cid:9) 240
111.1 Addition of Compliance to the Compressor 240
111.11 Verification of the Fluid Piston Equation 241
111.111 New Model for the Non-Return Valves 242
lII.IV New Model of the Heat Recovery Exchanger 243
IV PROGRAM FLOWSHEETS AND LISTINGS (cid:9) 245
IV.I First Model (cid:9) 245
IV.II Second Model (cid:9) 254
NOMENCLATURE (cid:9) 282
BIBLIOGRAPHY (cid:9) 289
VII
UST OF fiGURES
Development of Edinburgh Duck: Backless Flap (cid:9) 12
1.1 (cid:9)
12
Development of Edinburgh Duck: "Tadpole" (cid:9)
1.2 (cid:9)
12
Development of Edinburgh Duck: the Duck (cid:9)
1.3 (cid:9)
13
Development of Edinburgh Duck VC System (cid:9)
1.4 (cid:9)
14
1.5 (cid:9) Detail of Edinburgh Duck VC System (cid:9)
Cross Section through Spiral Plate
1.6 (cid:9)
15
Heat Exchanger (cid:9)
16
1.7 (cid:9) Inertial Loop Pump (cid:9)
56
2.1 Schematic of Simple Still
57
2.2 MEB Plant with 3 Stages
58
2.3 Schematic of MSF Plant
58
2.4 Temperature Profile Through MSF Plant
59
MSF Plant with Infinite Number of Stages
2.5
Temperature Profile Through MSF Plant
2.6
59
with Inifite Number of Stages
2.7 Specific Area vs. Performance Ratio
60
for MSF Plants
Total Cost vs. Number of Stages for MSF
2.8
60
and MEB Plants
61
2.9 Schematic of VTE Plant
62
2.10 Cross Section Through Double Fluted Tube
62
2.11 Schematic of Simple VC Unit
63
2.12 Simple RO Plant
63
Principle of ElectrodialVsis
2.13
64
2.14 Global Rainfall Patterns
65
2.15 Progressive Water Wave
65
2.16 Circulation Beneath Progressive Waves
66
2.17 Momentum Transfer in Water Waves
66
2.18 Simply Shaped Body in a Wave Field
67
2.19 Global Wave Climates
97
2 Chamber/4 Chamber Basis of the First Model
3.1
97
Definition of 6V for the First Model
3.2
vu'
(cid:9)(cid:9)(cid:9)(cid:9)(cid:9)(cid:9)
98
3.3 (cid:9) Fluid Piston as a U-Tube (cid:9)
98
Fluid Piston as a Solid Semi-Cylinder (cid:9)
3.4 (cid:9)
99
4 Chamber Basis of the Second Model (cid:9)
3.5 (cid:9)
3.6 (cid:9) Fractional Opening vs. Ap for the
99
Non-Return Valves (cid:9)
100
3.7 (cid:9) Definition of 6V for the Second Model (cid:9)
100
Heat Recovery Exchanger Model (cid:9)
3.8 (cid:9)
130
4.1 Early Design of Compressor
131
4.2 Compressor with Compliance Feedback Loop
132
4.3 Sketch of Still with Liquid and Vapour Lines
133
4.4 Distributor Components
134
4.5 Assembled Distributor
135
4.6 Feed Pre-Heater
136
4.7 Sketch of Single Shaft Compressor
137
4.8 Section through a Ball-Nut
138
4.9 Compressor Components
139
4.10 Development of Piston Design
140
4.11 Compressor Plan
-
141
4.12 Compressor - Elevation
142
4.13 Steady Carriage
142
4.14 Break Down of Control Functions
143
4.15 Piston Control Circuit Diagram
144
4.16 Simple Amplifier Circuit
145
4.17 Amplifier Circuit Diagram
146
4.18 Mounting Detail of LM12's
146
4.19 Mounting of Position Sensor
147
4.20 Mounting of Tachometer
148
4.21 P. and I. Diagram of Experimental Facility
149
4.22 Simple Flowsheet for MFI Communication
150
Improved Flowsheet for MFI Communication
4.23
151
Flowsheet for Disc Storage of MFI Programs
4.24
152
Flowsheet for Retrieval of Stored Programs
4.25
153
4.26 Parameters Stored in MFI Array
Flowsheet for MFI Control and
4.27
154
Monitoring Program
ix
4.28 Flowsheet for Control Parameter
155
Setting Program
156
4.29 Interface Circuit for BBC Microcomputer
157
4.30 Flowsheet for Menu System
158
4.31 Multiplexer Circuit Diagram
159
4.32 Solenoid Valve Relay Wiring Diagram
160
4.33 Tachometer i.c. Circuit Diagram
161
4.34 Opto-Isolator Ic. Circuit Diagram
162
435 Thermocouple Probe Assemblies
162
4.36 Level Measurement Boxes
182
5.1 Plot of Ap vs. 8 from equation (5.1)
182
5.2 Plot of Ap vs. 0 from the First Model
5.3 Plots of Ap vs. t for Time Dependency
183
Testing; First Model
184
5.4 Output vs. A/T; First Model
184
5.5 SEC vs. Output; First Model
185
5.6 Output vs. Area; First Model
185
5.7 Output VS. Tfeed; First Model
186 - 194
5.8 - .24 Plots of AP vs. 0;
Experimental and Predicted for Various
Amplitudes and Periods
195 - 203
5.25 - .41 Plots of APsim V5. APexp
for Various Amplitudes and Periods
5.42 Gradient, Intercept and Period from
204
Figures (5.25) to (5.41) vs. Period
5.43 Gradient. Intercept and Period from
205
Figures (5.25) to (5.41) vs. Amplitude
206 - 214
5.44 - .60 Plots of p vs. 8;
Experimental and Predicted
for Various Amplitudes and Periods
5.61 Transient Behaviour Prediction from
214
the Second Model
5.62 Output vs. Period and Amplitude from
215
the Second Model
x