air-conditioning system by using district cooling...
TRANSCRIPT
AIR-CONDITIONING SYSTEM
BY USING DISTRICT COOLING SYSTEM (DCS):
THERMAL ENERGY STORAGE (TES) TECHNOLOGY
NORDIANA BINTI MOHD HATTA
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
“I admit that had read this dissertation and in my opinion this dissertation
is satisfactory in the aspect of scope and quality for the bestowal of
Bachelor of Mechanical Engineering (Design and Innovation)”
Signature:
Name of Supervisor 1: Mr. Safarudin Gazali Herawan
Date:
Signature :
Name of Supervisor 2: Mr. Afzanizam
Date:
AIR-CONDITIONING SYSTEM
BY USING DISTRICT COOLING SYSTEM (DCS):
THERMAL ENERGY STORAGE (TES) TECHNOLOGY
NORDIANA BINTI MOHD HATTA
This report was submitted in accordance
with the partial requirement for the honor of
Bachelor of Mechanical Engineering (Design and Innovation)
Faculty of Mechanical Engineering
Universiti Teknikal Malaysia Melaka
APRIL 2009
ii
“I verify that this report is my own word except summary and extract that
every one of it I have clarify the resource”
Signature:
Writer Name: Nordiana binti Mohd Hatta
Date:
iv
ACKNOWLEDGEMENT
I would like to acknowledge and extend my heartfelt gratitude to the
following persons who have made the completion of this Projek Sarjana Muda
(PSM) report possible. I would like to express my deep and sincere gratitude to my
supervisor, Mr. Safarudin Gazali Herawan, His wide knowledge and his logical way
of thinking have been of great value for me. I am deeply grateful for his detailed and
constructive comments, and for his important support throughout this work.
I wish to express my warm and sincere thanks to Mr. Amiruddin Ghazali,
Head of Section of TNEC and Mr. Sharulnizam Shariff, Plant Supervisor of TNEC
who gave me the opportunity to gain knowledge and experiences about the DCS and
TES systems that wholly-liable under TNB Engineering Corporation (TNEC) and
gave me untiring help during my difficult moments. I owe my most gratitude to Mr.
Nazree Abdullah, Senior Technician of TNEC for his valuable advice and friendly
help. Their extensive discussions around my work and interesting explorations in
operations have been very helpful for my PSM.
During this work I have collaborated with many colleagues for whom I have
great regard, and I wish to extend my warmest thanks to all those who have helped
me with my work. The generous support from all of you is greatly appreciated. I
cannot end without thanking my family, on whose constant encouragement and love
I have relied throughout my time at the university. Their unflinching courage and
conviction will always inspire me, and I hope to continue, in my own small way, the
noble mission to which they gave their lives. It is to them that I dedicate this
knowledge and experience. And to God, who made all things possible.
v
ABSTRACT
This study is about the air conditioning system by using District Cooling
System (DCS) with the Thermal Energy Storage (TES) technology. DCS is a system
where a central chiller plant provides chilled water for air-conditioning purposes for
multiple buildings. Whereas TES is the storage of cooling energy during low air-
conditioning loads period and used later to meet the air-conditioning loads. TES can
be further broken down into ice harvesting, ice-on-coil, ice slurry, and encapsulated
ice options. Ice-on-coil systems may be internal-melt or external-melt and may be
charged and discharged with refrigerant or a single-phase coolant (typically a
water/glycol mixture). Ice-on-coil systems come in several variations. In all
variations, ice is formed on a heat transfer surface (generically referred to as a
“coil”) without being released during the charging mode and melted away during the
discharge mode. Ice-harvesting systems form ice on coils or other refrigerant
evaporating surfaces and periodically release the ice into a storage tank that contains
a mixture of ice and water. Ice slurry systems produce small particles of ice within a
solution of glycol and water, resulting in a slushy mixture that can be pumped.
Encapsulated ice systems consist of water contained in plastic containers surrounded
by coolant, all contained within a tank or other storage vessel. Within this report, all
of these systems will differentiate by the storage system technologies, the
mechanism, design and operating systems. Considering the pros and cons, the most
suitable system will choose. The reasons of choosing that system as the best option
will briefly explain. Moreover, the cooling load of FKM blocks in Durian Tunggal
will calculate by using Carmel software. The overview of the software is preview,
also the data insertion, check and end result. There are two types of outcomes of the
program which consisting of result output and graph output. The most appropriate
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capacity/types of equipments that could go well with the system would be selected in
order to ensure the system can operate efficiently. These equipments comprise of
STL tank, chiller, cooling tower, heat exchanger and air-handling unit (AHU).
The end part of this report will gives general conclusion on this study. It also include
a suggestion to continue the research on this topic for better understanding on the
refrigeration system and more to the point of obtaining the most competent cooling
system in order to reduce its monthly expenses but with higher efficiency and give
much benefits to the consumers.
vii
ABSTRAK
Kajian ini adalah mengenai sistem penyejukan udara menggunakan Sistem
Pendingin Lingkungan (District Cooling System-DCS) dengan teknologi Tenaga
Pendam Lakuran (Thermal Energy Storage-TES). DCS ialah sistem di mana pusat
chiller plant membekalkan air sejuk untuk tujuan penyejukan bagi beberapa
bangunan sekitar. Manakala TES adalah penyimpanan tenaga penyejukan pada
waktu beban penyejukan rendah dan akan digunakan kemudian ketika tenaga
penyejukan itu diperlukan. TES terbahagi kepada beberapa jenis iaitu ice harvesting,
ice-on-coil, ice slurry dan encapsulated ice Sistem Ice-on-coil terbahagi kepada dua
iaitu pencairan dalam (internal-melt) dan pencairan luar (external-melt) di mana ia
akan dicaj dan nyahcaj menggunakan bahan penyejuk atau cecair penyejuk satu fasa
(biasanya campuran air/glikol). Terdapat pelbagai variasi di dalam sistem ice-on-coil
di mana di dalam semua variasi, ais terbentuk pada permukaan haba dipindahkan
(disebut sebagai “coil”) tanpa dibebaskan semasa pengecasan dan ais mencair
semasa penyahcasan. Sistem ice harvesting membentuk ice-on-coil atau permukaan
sejatan bahan penyejuk lain dan menyalurkan ais secara berperingkat ke dalam
tangki yang mengandungi campuran ais dan air. Sistem ice slurry menghasilkan ais
yang kecil di dalam larutan glikol dan air menjadikan ia sebagai larutan separa cair
yang boleh dipam. Sistem kapsul ais (encapsulated ice) adalah kapsul plastik yang
mengandungi air dan dikelilingi oleh cecair penyejuk di dalam sebuah tangki atau
bekas penyimpanan lain. Di dalam laporan ini, sistem-sistem ini akan dibezakan
melalui teknologi sistem penyimpanan, mekanisma, rekabentuk serta sistem operasi
setiap satunya. Selepas mengambil kira kelebihan dan kekurangan, system yang
paling sesuai akan dipilih dan sebab-sebab sistem ini dipilih akan dijelaskan. Beban
penyejukan bagi blok FKM di durian tunggal akan dikira menggunakan perisian
Carmel. Sedikit gambaran tantang program perisian akan diterangkan beserta
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cara memasukkan data, penyemakan dan hasil akhir. Terdapat dua jenis hasil iaitu
keputusan teks dan graf. Kelengkapan lain berkaitan sistem ini seperti tagki STL,
chiller, menara penyejuk, penukar haba dan air handling unit (AHU) akan dipilih
berdasarkan kapasiti/jenis yang terbaik yang dapat memaksimakan kecekapan
sistem. Kesimpulan mengenai kajian disertakan di akhir laporan yang juga
merangkumi cadangan untuk meneruskan kajian berkenaan topik ini dengan tujuan
untuk lebih memahami tentang sistem penyejukan dan lebih menjurus kepada
menghasilkan sistem yang kompeten untuk mengurangkan kos bulanan dan dalam
masa yang sama merupakan sistem yang efisien serta memberi banyak kelebihan
kepada pengguna.
ix
TABLE OF CONTENT
CHAPTER TITLE PAGE
DECLARATION ii
DEDICATION iii
ACKNOWLEDGEMENT iv
ABSTRACT v
ABSTRAK vii
TABLE OF CONTENT ix
LIST OF TABLES xiv
LIST OF FIGURES xv
LST OF SYMBOLS xvii
LIST OF ABBREVIATIONS xix
LIST OF APPENDIX xx
CHAPTER I INTRODUCTION 1
1.1 Background 1
1.2 Problem Statement 2
1.3 Objectives 3
1.4 Scope of Study 3
CHAPTER II LITERATURE REVIEW 5
2.1 District Cooling System (DCS) 5
2.1.1 Overview of DCS 5
x
CHAPTER TITLE PAGE
2.1.2 The District Cooling System (DCS)
Concept
7
2.1.3 The Benefits of DCS 8
2.2 Thermal Energy Storage (TES) 9
2.2.1 Overview of TES 9
2.2.2 Economics of Thermal Storage 10
2.2.3 Other Benefits 12
2.2.4 Storage System Technologies 14
2.2.4.1 Chilled Water Storage 14
2.2.4.2 Ice storage 17
2.2.4.3 Eutectic Salts Storage 21
2.2.5 The Variations of Mechanisms 22
2.2.5.1 Chilled Water System 22
2.2.5.2 Ice Storage System 25
2.2.5.3 Eutectic Salt Systems 32
2.2.6 The Variations of Design and Operating
Strategies
33
2.2.6.1 Full Storage System 33
2.2.6.2 Partial Storage 34
CHAPTER III METHODOLOGY 36
3.1 Introduction 36
3.2 Implementation Flow Chart 37
3.3 Carmel Software 38
3.4 Loadsoft 6.0 Software 40
3.5 Data Insertion, Checks and Outputs 41
3.5.1 Terminology 41
3.5.2 Data Insertion 43
3.5.3 Checks 60
xi
CHAPTER TITLE PAGE
3.5.4 Outputs 61
3.5.4.1 Calculation Month and Time
Range
62
3.5.4.2 Standard Outputs 63
3.5.4.3 What-If Scenario Outputs 64
3.5.5 Report Description 64
3.5.5.1 System/Area Heating and Cooling
Load Summary Report
64
3.5.5.2 Breakdown of All Load
Components Report
65
3.5.5.3 Detailed Psychrometric Analysis
Report
67
3.5.5.4 Wall and Window Load Summary
Report
67
3.5.5.5 Graph Outputs 68
3.6 Equipment Selection 70
3.6.1 STL Tank 70
3.6.1.1 Atmospheric Tank Option 71
3.6.1.2 Pressurized Tank design Option 72
3.6.2 Chillers 73
3.6.2.1 Types of Chillers 74
3.6.3 Cooling Tower 77
3.6.3.1 Type of Cooling Tower 77
3.6.3.2 Water Treatment 79
3.6.4 Heat Exchanger 80
3.6.4.1 Types of Heat Exchanger 80
3.6.5 Air Handling Unit (AHU) 82
3.6.5.1 Temperature Control 84
3.6.5.2 Humidity Control 84
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CHAPTER TITLE PAGE
CHAPTER IV RESULT 85
4.1 Introduction 85
4.2 DCS Incorporating With TES Technology 86
4.3 Results/Outputs of Carmel Software 86
4.3.1 System/Area Heating and Cooling
Load Summary Report
87
4.3.2 Breakdown of All Load Components
Report
89
4.3.3 Detailed Psychrometric Analysis
Report
91
4.3.4 Wall and Window Load Summary
Report
92
4.3.5 Graph Output 93
4.4 Result Analysis 95
CHAPTER V DISCUSSION 96
5.1 Introduction 96
5.2 Equipment Selection 97
5.2.1 Encapsulated Ice 97
5.2.1.1 Benefits of Using Ice Balls 99
5.2.1.2 Basic System Operation 100
5.2.1.3 Modular Tanks vs. Encapsulated
Ice Storage
101
5.2.2 STL Tank 104
5.2.2.1 Inventory Tank 104
5.2.2.2 STL Tank Size Determination 105
5.2.3 Chiller 107
5.2.3.1 Centrifugal Chiller 108
5.2.4 Cooling Tower 109
xiii
CHAPTER TITLE PAGE
5.2.5 Heat Exchanger 110
CHAPTER IV CONCLUSION AND SUGGESTION 112
6.1 Conclusion 112
6.2 Suggestion 112
REFERENCES 114
BIBLIOGRAPHY 116
APPENDIX A 118
APPENDIX B 120
APPENDIX C 128
xiv
LIST OF TABLE
TABLE TITLE PAGE
2.1 Comparison of alternative thermal storage technologies 14
4.1 Benefits of using ice balls 99
4.2 Typical tank size dimension 106
xv
LIST OF FIGURES
FIGURE TITLE PAGE
2.1 Typical DCS configuration 7
2.2 Typical design day chilled water load profile 11
2.3 How TES technology saves energy cost 13
2.4 Chilled water storage tank with siphon baffles 16
2.5 Ice shedder thermal storage system schematic 18
2.6 External melt coil freezing thermal storage system
schematic
19
2.7 Internal melt coil freezing thermal storage system
schematic
20
2.8 Chilled water stratification 24
2.9 Typical chilled water configuration 24
2.10 Typical ice-harvesting configuration 26
2.11 External-melt ice-on-coil 27
2.12 Internal melt ice-on-coil 27
2.13 Direct refrigerant external-melt ice-on-coil
configuration
28
2.14 Secondary coolant external-melt ice-on-coil
configuration
28
2.15 Typical internal-melt ice-on-coil configuration 29
2.16 Typical Ice Slurry Configuration 30
2.17 Encapsulated ice balls 31
2.18 Typical encapsulated ice configuration 31
2.19 Eutectic salt container 32
2.20 Typical eutectic salt configuration 32
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FIGURE TITLE PAGE
2.21 Full storage 33
2.22 Partial storage – load leveling 34
2.23 Partial storage – demand limiting 35
3.1 Implementation flow chart 37
3.2 Software program from Carmel 39
3.3 Basic data input 44
3.4 System inputs 45
3.5 Air volume calculation type / pretreating 47
3.6 Zone inputs 48
3.7 General area 49
3.8 Wall and roof envelope 50
3.9 Wall CTS number 51
3.10 Roof CTS number 52
3.11 Window envelope 53
3.12 Window SHGC properties 53
3.13 Window construction U-value 54
3.14 Door envelope 55
3.15 Internal / other 56
3.16 People activity level 56
3.17 Schedule 58
3.18 Appliance list 59
3.19 Checks/outputs 61
3.20 Display Report 1 63
3.21 Display Report 2 63
3.22 Graphing output option 69
3.23 Atmospheric Tank System 72
3.24 Pressurized tank system 73
3.25 Centrifugal chiller 75
3.26 Reciprocating chiller 76
xvii
FIGURE TITLE PAGE
3.27 Screw chiller 76
3.28 Cross flow cooling tower 78
3.29 Cross flow cooling tower system 78
3.30 Counter flow cooling tower 79
3.31 Counter flow cooling tower system 79
3.32 Shell and tube heat exchanger 81
3.33 Plate heat exchanger 82
3.34 Plate fin heat exchanger 82
3.35 Air handling unit 83
4.1 Horizontal bar chart 93
4.2 Pie chart 94
4.3 Line chart 94
5.1 Ice ball characteristic 98
5.2 Charging and discharging process of ice ball 98
5.3 Charging cycle 100
5.4 Discharging cycle 100
5.5 Standby mode 101
5.6 Modular ice storage tanks 102
5.7 Encapsulated ice 103
5.8 Centrifugal chiller parts 108
5.9 Reduction in chiller capacity usage 110
5.10 Cooling tower crossflow type design 111
5.11 Plate heat exchanger (PHE) 113
5.12 Partial storage – load leveling 114
xviii
LIST OF SYMBOLS
BTU = British Thermal Unit
C = Celsius
CFM = Cubic Feet Meter
F = Fahrenheit
hr = Hour
J = Joule
J/kg = Joule per kilogram
K = Kelvin
kg = Kilogram
KJ = Kilojoules
kPA = Kilopascal
kW = Kilowatt
kW/h = Kilowatt per Hour
kWh = Kilowatt hour
m3
= Cubic meters
m3/hr = Cubic meters per Hour
mm = Millimeter
RT = Refrigerant ton
RTHr = Refrigerant ton hour
SqFt = Square feet
SqM = Square meter
Ton-Hr = Ton hour
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LIST OF ABBREVIATION
ASHRAE = American Society of Heating, Refrigerating and
Air-Conditioning Engineers
CMA = Calcium Magnesium Acetate
COP = Coefficient of Performance
CTS = Conduction Time Series
DCS = District Cooling System
DX = Direct Expansion
FKM = Fakulti Kejuruteraan Mekanikal
(Faculty of Mechanical Engineering)
HCFC = Hydrochlorofluorocarbons
HFC = Hydrofluorocarbon
HVAC = Heating, Ventilating and Air-Conditioning
HW = Heavy Weight
IP = Inch-Pound
L/s = Litres per second
O&M = Operation and Maintenance
PSM = Projek Sarjana Muda
RTS = Radiant Time Series
SHGC = Solar Heat Gain Coefficient
SI = System International
STL = Storage Thermal Latent
TES = Thermal Energy Storage
TNB = Tenaga Nasioanal Berhad
TNEC = TNB Engineering Corporation
UTeM = Universiti Teknikal Malaysia Melaka
VAV = Variable Air Volume
xx
LIST OF APPENDIX
APPENDIX TITLE PAGE
A Gantt Chart 118
B Data Insertion in Carmel Software and Graph Output 120
C FKM Block Floor Plan 128
1
CHAPTER I
INTRODUCTION
1.1 Background
Referred to Robert (2003), there are two types of HVAC systems designed to
satisfied building cooling requirements; direct expansion (DX) systems, in which
there is direct heat exchange between the building air and the refrigerant, and
secondary refrigerant systems that utilize chilled water as an intermediate heat
exchange medium to transfer heat from the building air to the refrigerant which we
called it centralized cooling system or commercially named Direct Cooling System
(DCS).
Basically, a DCS distributes thermal energy in the form of chilled water or
other media from a central source to multiple buildings through a network of
underground pipes for use in space and process cooling. The cooling or heat
rejection is usually provided from a central cooling plant, thus eliminating the need
for separate systems in individual buildings. In DCS there is one new technology
which called Thermal Energy Storage (TES). This type of system has been use
widely in overseas but only introduced in Malaysia for about few years.
Thermal Energy Storage capitalizes on the cheaper off-peak tariff offered by
the electric utility company. The system produces cooling energy at night when the
electricity tariff is low. During the day, when the air-conditioning demand is high,
2
the stored cooling energy is released by circulating chilled water through the storage
system and onto the buildings. Only a limited amount of chiller capacity needs to
operate during this period. By adopting this concept, the plant consumes less
electricity during the day, when electricity tariff is high. This leads to significant
savings in operating costs. As the electrical power demand for this plant is also low
during the day, further cost saving is achieved through reduced maximum demand
charges.
There are many different types of thermal storage systems representing
different combinations of storage media, charging mechanisms, and discharging
mechanisms. The basic media options are water, ice, and eutectic salts. This system
can be further broken down into ice harvesting, ice-on-coil, ice slurry, and
encapsulated ice options.
1.2 Problem Statement
The purpose of the study is to find an approach in order to get lower cost and
high efficiency for air-conditioning system. Almost every commercial buildings and
offices have an air conditioning unit. It has become necessity of modern life. There
are two major options to distribute cooling energy to building which are direct
expansion system and centralized system. For the average sized of office and home,
the trend is to use building-specific cooling that is a split air conditioning unit. For
large and/or multiple buildings, it make use of central air conditioning unit which
also called District Cooling System (DCS). District cooling means the centralized
production and distribution of cooling energy. Commonly, many building which
applied this DCS system would use water as a refrigerant. This system will cost high
monthly expenses of the electricity consumption of the system also for the
maintenance and services. This is because the water chillers will be operated all the
time as required to supply cooling energy into buildings and normally the demand is
during peak hours. In order to solve this problem, there is new development of
refrigeration technology called Thermal Energy Storage (TES). TES can reduce cost
by shifting the electricity consumption from day to night. With this system, the