UNIVERSITI TEKNIKAL MALAYSIA MELAKA

ENHANCE THE PERFORMANCE OF CONDENSER BY USING

EVAPORATIVE COOLING METHOD FOR SPLIT TYPE AIR

CONDITIONER

This report is submitted in accordance with requirement of the Universiti Teknikal

Malaysia Melaka (UTeM) for the Bachelor of Engineering Technology

(Refrigeration & Air-Conditioning System) with Honours

By

KARTHIGEYAN A/L RAMAKRISHNAN

B071210541

910410-08-5653

FACULTY OF ENGINEERING TECHNOLOGY

2016

DECLARATION

I hereby, declared that this report entitled “Enhance the performance of condenser by

using evaporative cooling method for split type air conditioner” is the results of my

own research except for quotes as cited in references.

Signature : ………………………………………….

Author’s Name : ………………………………………….

Date : ………………………………………….

APPROVAL

This report is submitted to the Faculty of Engineering Technology of Universiti

Teknikal Malaysia Melaka (UTeM) as a partial fulfillment of the requirements for

the award of Bachelor of Mechanical Engineering Technology (Refrigeration & Air-

Conditioning Systems) with Honours. The member of the supervisory is as follow:

………………………………

(Mr. Azwan Bin Aziz)

i

ABSTRAK

Penyaman udara jenis unit terpisah adalah salah satu peralatan yang biasa digunakan di kediaman, bangunan, pejabat dan hotel. Penyaman udara jenis ini dibahagikan kepada dua bahagian iaitu unit pemeluwap dan unit gegelung kipas (unit dalam). Unit pemeluwapan terletak di luar bangunan manakala unit gegelung kipas (unit dalam) terletak di ruang penyamanan dan kedua-dua unit ini disambungkan dengan menggunakan tiub kuprum. Penyaman udara jenis unit terpisah kebanyakkannya menggunakan pemeluwap sejuk udara dan pekali prestasi sistem penyaman udara yang menggunakan pemeluwap jenis ini bergantung pada suhu persekitaran. Dalam keadaan cuaca yang panas, pekali prestasi penyaman udara akan menurun dan ia akan meningkatkan penggunaan tenaga elektrik. Pengurangan penggunaan tenaga elektrik adalah salah satu kebimbangan yang paling penting dalam keadaan cuaca panas. Penyejukan penyejatan adalah salah satu kaedah yang boleh meningkatkan pekali prestasi sistem dalam persekitaran panas. Pad penyejukan dipasang pada belakang unit pemeluwap yang sedia ada. Pam air digunakan untuk menyembur air pada pad penyejukan supaya dapat mengurangkan suhu udara persekitaran apabila melalui pad penyejukan dan seterusnya ke gegelung pemeluwap. Dengan menggunakan kaedah ini, kadar pekali prestasi sistem meningkat pada masa yang sama suhu udara persekitaran diturunkan. Keputusan kajian ini menunjukkan bahawa dengan menggunakan sistem penyejatan, kadar pekali sistem penyejukan dapat ditingkatkan 20.4% dan penggunaan tenaga elektrik dapat dikurangkan 10.2% pada suhu persekitaran 34˚C. Sistem penyejukan penyejatan ini dianggap sebagai kaedah yang mempunyai kos rendah, mesra alam dan cekap tenaga untuk meningkatkan prestasi pemeluwap sejuk udara bagi penyaman udara jenis terpisah.

ii

ABSTRACT

Split-type air conditioner is one of the commonly used appliances in residence, building, offices and hotels. This type of air conditioners divided into two parts which is condensing unit and fan coil unit. Condensing unit normally situated at the outside of the building whereas fan coil unit fixed in the conditioned space and both units connected through copper pipes. An air-cooled condenser is normally used in this type of air conditioner and the coefficient of performance of system using air-cooled condenser is depends on the temperature of ambient air. In hot environment, the coefficient of performance of the air conditioning system decreasing thus results increasing in electrical power consumptions. Minimizing of energy consumption is a major concern especially in the hot weather conditions. An evaporative cooling method can enhance the coefficient of performance of the system in hot ambient. The conventional condensing unit of split-type air conditioner retrofitted with evaporative cooling pad at the up stream of the condenser. A water pump is used to inject the water over the cooling pad to reduce the ambient air temperature when passes over the cooling pad and then passes over the condenser coil. Application of evaporative cooling system couple with air-cooled condenser can increase the coefficient of performance of the air conditioning system and the rate of COP improvement is increased as the ambient air temperature decreased. The result shows that by using evaporative cooling method, the COP of the air conditioner improved up to 20.4% and electrical current consumption reduced up to 10.2% at 34˚C ambient temperature. This evaporative cooling system considered as low cost, environmental friendly and energy efficient method to enhance the performance of air-cooled condenser of split-type air conditioner.

iii

DEDICATION

There are a number of people without whom this thesis might not have been

written, and to whom I am greatly indebted. I owe my gratitude to all those people

who have made this project possible and because of whom my graduate experience

has been one that I will cherish forever. I dedicate my dissertation work to my family

and many friends. A special feeling of gratitude to my loving parents, Ezhilarasi A/P

Sababathy whose have been my constant source of inspiration. They have given me

the drive and discipline to tackle any task with enthusiasm and determination.

Without their love and support this project would not have been made possible. My

deepest gratitude is to my advisor, Mr. Azwan Bin Aziz. I have been amazingly

fortunate to have an advisor who gave me the freedom to explore on my own and at

the same time the guidance to recover when my steps faltered. He taught me how to

question thoughts and express ideas. His patience and support helped me overcome

many crisis situations and finish this project. I hope that one day I would become as

good an advisor to my students as he has been to me. Many friends have helped me

through these difficult years. Their support and care helped me overcome setbacks

and stay focused on my graduate study. I greatly value their friendship and I deeply

appreciate their belief in me. Particularly, I would like to acknowledge Elvin for

helping me develop my drawing skills. Besides I am also thankful to lecturers for

numerous discussions on related topics that helped me improve my knowledge in the

research area better. All of them have been my best cheerleaders.

iv

ACKNOWLEDGEMENT

I would like to express my deepest gratitude to the All Mighty for His

goodness and grace that sustained my performance level at the crucial times of

completing this Final Year Project entitled Enhance the Performance of Condenser

by Using Evaporative Cooling Method for Split Type Air Conditioner. Besides that, I

would like to extend my appreciation to those who contributed time, concern and

efforts to lend a helping hand thus allow me to gain valuable knowledge. On top of

that, a special thanks to my supervisor, Mr. Azwan Bin Aziz for his guidance,

encouraging excellence in mentoring and most of all patience throughout the entire

project development. Thanks to my bachelor degree project group mates who are

helping for completing the researches together. Next, I would like my academic

advisor, Mr Muhammad Fairuz Bin Abu Bakar, the beginning teachers, mentor-

teachers and administrators of our university faculty that assisted me with this

research. Finally, I would also like to express my endless appreciation to my family

members for their valuable support and motivations. It would not have been possible

to complete this project without their supports.

v

TABLE OF CONTENTS

ABSTRAK. .................................................................................................................... i

ABSTRACT .................................................................................................................. ii

DEDICATION ............................................................................................................. iii

ACKNOWLEDGEMENT ........................................................................................... iv

TABLE OF CONTENTS ............................................................................................... v

LIST OF TABLES ....................................................................................................... ix

LIST OF FIGURES ....................................................................................................... x

LIST OF ABBREVATIONS, SYMBOLS AND NOMENCLATURES ................... xii

CHAPTER 1: INTRODUCTION ............................................................................... 1

1.1 Background of the Study ............................................................................. 1

1.2 Problem Statements ..................................................................................... 2

1.3 Objectives of The Study .............................................................................. 3

1.3.1 Main Objective: .................................................................................... 3

1.3.2 Specific Objectives: .............................................................................. 3

1.4 Work Scope of The Study ............................................................................ 3

CHAPTER 2: LITERATURE REVIEW ................................................................... 5

2.1 Introduction .................................................................................................. 5

2.2 Performance of Air-cooled Condenser ........................................................ 5

2.3 Application of Evaporative Cooling for Air-cooled Condenser .................. 6

2.4 Water Spray Mist Pre-Cooling System ........................................................ 8

2.5 Direct Evaporative Cooling (DEC) System ................................................. 9

2.6 Evaporative Cooling Pad ........................................................................... 10

2.7 Selection Criteria for Evaporative Cooling Pad ........................................ 10

2.8 The Effect of Air Velocity and Cooling Pad Thickness ............................ 11

2.9 The Effect of Water Flow Rate .................................................................. 12

vi

2.10 Pressure Drop across the Cooling Pad ....................................................... 12

2.11 Water Evaporation from the Cooling Pad .................................................. 12

2.12 Air Conditioner Condenser Fan Performance ........................................... 13

2.13 Impact of Air Flow on Condensing Unit ................................................... 14

2.14 Condenser Fan Sound Control ................................................................... 14

CHAPTER 3: METHODOLOGY ............................................................................ 16

3.1 Introduction ................................................................................................ 16

3.2 Project Planning ......................................................................................... 16

3.3 Flowchart of The Project ........................................................................... 17

3.4 Equipments and Materials ......................................................................... 18

3.4.1 Split type air conditioner .................................................................... 18

3.4.2 Evaporative cooling pad ..................................................................... 19

3.4.3 Water pump ........................................................................................ 19

3.4.4 Thermocouple ..................................................................................... 20

3.4.5 Pressure gauge .................................................................................... 21

3.4.6 Clamp meter ....................................................................................... 21

3.4.7 Flaring and swaging tools ................................................................... 22

3.4.8 Copper tube cutter .............................................................................. 23

3.4.9 Welding gas and torch ........................................................................ 23

3.4.10 Accessories and fittings ...................................................................... 24

3.4.11 Copper tubing ..................................................................................... 25

3.5 Designing the Model using Solidwork Software ....................................... 26

3.5.1 Development of design ....................................................................... 26

3.6 Development of the Project ....................................................................... 29

3.7 Working Principle of the Project ............................................................... 32

3.8 Analysis Method ........................................................................................ 33

vii

CHAPTER 4: RESULTS & DISCUSSIONS ........................................................... 34

4.1 Introduction ................................................................................................ 34

4.2 Specific Parameters Results ....................................................................... 34

4.2.1 Sketching Pressure-Enthalpy Chart .................................................... 36

4.3 Performance Analysis and Discussion ....................................................... 38

4.3.1 Effect of Ambient Temperature to the Coefficient of Performance of

the System .......................................................................................... 38

4.3.2 Effect of Ambient Temperature to Cooling Effect of the System ...... 39

4.3.3 Effect of Ambient Temperature to the Compressor Work ................. 41

4.3.4 Effect of Ambient Temperature to the Electric Current Consumption

of the System ...................................................................................... 42

4.3.5 Reduction of Condenser Inlet Air Temperature Using Evaporative

Cooling Method ................................................................................. 44

4.3.6 Discussion on the Performance Analysis ........................................... 45

4.4 Water Evaporation Rate ............................................................................. 46

4.4.1 Discussion on Water Evaporation Rate .............................................. 47

CHAPTER 5: CONCLUSIONS & FUTURE WORK ............................................ 49

5.1 Introduction ................................................................................................ 49

5.2 Summary of the Experimental Study ......................................................... 49

5.3 Conclusions ................................................................................................ 50

5.4 Recommendations ...................................................................................... 51

5.5 Limitation................................................................................................... 51

REFERENCES ........................................................................................................... 52

viii

APPENDIX A………………………………………………………………….…...56

APPENDIX B………………………………………………………………………57

APPENDIX C………………………………………………………………………58

APPENDIX D………………………………………………………………………59

ix

LIST OF TABLES

Table 4.1: Experimental data for temperature at various ambient temperatures ......... 35

Table 4.2: Experimental data for pressure at various ambient temperatures ............... 36

Table 4.3: Enthalpy of R-22 refrigerant at various ambient temperatures ................... 37

Table 4.4: Different of COP of the system between conventional and evaporative

cooling with the increase of ambient temperature ...................................... 38

Table 4.5: Different of cooling effect between the conventional and evaporative

cooling with the increase of ambient temperature ...................................... 40

Table 4.6: Comparison of compressor work between the conventional and

evaporative cooling with the increase of ambient temperature .................. 41

Table 4.7: Comparison of electric current consumption between conventional and

evaporative cooling system with different ambient temperature................ 43

Table 4.8: Water evaporation rate at different ambient temperature ........................... 46

x

LIST OF FIGURES

Figure 2.1: Schematic diagram of evaporative cooling system (Chaktranond and

Doungsong, 2010) ....................................................................................... 7

Figure 2.2: Schematic of the air-cooled chiller with water mist system

(Jia Yang et al., 2012) ................................................................................. 9

Figure 3.1: Flowchart of the project ............................................................................. 17

Figure 3.2: Split type air conditioner (Model National) .............................................. 18

Figure 3.3: Corrugated cellulose cooling pad .............................................................. 19

Figure 3.4: Submersible water pump ........................................................................... 20

Figure 3.5: K-type two channel digital thermocouple ................................................. 20

Figure 3.6: Bourdon pressure gauge ............................................................................ 21

Figure 3.7: Digital clamp meter ................................................................................... 22

Figure 3.8: Flaring and swaging tools .......................................................................... 22

Figure 3.9: Copper tube cutter ..................................................................................... 23

Figure 3.10: Welding gas with torch ............................................................................ 24

Figure 3.11: Accessories and fittings ........................................................................... 24

Figure 3.12: Copper tubing .......................................................................................... 25

Figure 3.13: Model of condensing unit of split type air conditioner ........................... 26

Figure 3.14: Model of corrugated evaporative cooling pad ......................................... 27

Figure 3.15: Complete model of the experimental study ............................................. 28

Figure 3.16: Inside view of condensing unit ................................................................ 29

Figure 3.17: Condenser coil and Tee ........................................................................... 29

Figure 3.18: Brazed Tee with access valve .................................................................. 30

Figure 3.19: Flaring process ......................................................................................... 30

Figure 3.20: Condensing unit with pressure gauge ...................................................... 31

Figure 3.21: Condensing unit and indoor unit of air conditioner ................................. 31

Figure 3.22: Vacuum process ....................................................................................... 32

Figure 3.23: Condensing unit retrofitted with evaporative cooling pad ...................... 32

Figure 4.1: Graph of coefficient of performance against ambient temperature ........... 39

Figure 4.2: Graph of cooling effect against ambient temperature ............................... 40

Figure 4.3: Graph of compressor work against ambient temperature .......................... 42

xi

Figure 4.4: Comparison chart of electric current consumption against ambient

temperature ................................................................................................ 43

Figure 4.5: Condenser inlet air temperature against ambient temperature .................. 44

Figure 4.6: Graph of water evaporation rate against ambient temperature .................. 47

xii

LIST OF ABBREVATIONS, SYMBOLS AND

NOMENCLATURES

A - Ampere

ARI - Air-Conditioning and Refrigeration Institute

COP - Coefficient of Performance

CTC - Condenser Temperature Control

CV - Conventional

DBT - Dry Bulb Temperature

DC - Direct Current

DEC - Direct Evaporative Cooling

EC - Evaporative Cooling

NDDCT - Natural Draft Dry Cooling Tower

OD - Outer Diameter

PVC - Polyvinyl Chloride

RH - Relative Humidity

TWBT - Thermodynamic Wet Bulb Temperature

WSMCST - Water Spray Mist Cooling System with a Tor

1

CHAPTER 1 INTRODUCTION

1.1 Background of the Study

Nowadays, air conditioning is widely used during summer seasons and hot

weather countries. There are many types of air conditioning systems are available in

market. The most commonly used small tonnage air conditioning system at

residential, offices, shops, small industries are window air conditioner and split air

conditioner. But, the window air-conditioner is no more in market because of its

some disadvantages such as high noise level, higher power consumption, difficulties

in installation and etc. But, split type air-conditioner is currently much familiar than

the window air conditioner due to some of its advantages. This split type air

conditioner divided into two parts which is condensing unit normally known as

outdoor unit located at the outside of the building and fan coil unit normally known

as indoor unit located at the conditioned space.

The finned-tube air-cooled condenser is generally used in split type air

conditioning and refrigeration application because of its ease of installation,

simplicity of operation and maintenance and also the less maintenance cost as

compared water-cooled condensers. In air conditioning and refrigeration system, the

function of condenser is to reject heat from the refrigerant in vapour state and

condense it to the liquid state by condensation. The power consumption is an

importance in vapour compression cycle those using air-cooled condenser in hot

weather instead of water-cooled condenser. According to Chow, Lin and Yang,

(2002), the performance of air-cooled condenser based on heat transfer between the

condenser coils and the airflow through the condenser coil. When the condenser

temperature increases it will also causes the pressure of the system increase and

2

consequently result in increase the power consumption because the pressure ratio

becomes higher and the compressor is forced to work.

In this regard, to overcome the increase in temperature, a higher airflow rate is

required by an air-cooled condenser for enhance its performance, and it sometimes

causes some increase in sound level. So in general, by reducing the condenser

temperature and increasing the capacity of cooling and heat rejection, COP of the

system can be improved. The direct evaporative cooler is coupled with the air-cooled

condenser for the purpose of reduce the ambient air temperature. The evaporative

cooling pads are fixed at the upstream of the air cooled condenser and inject water on

the cooling pad using water pump. The water flows down due to gravity and when

the hot ambient air enter through the evaporative cooling pad, its temperature

reduced before passes over the condenser coil to enhance the air cooled condenser

performance of split type air conditioner, Luis Perez- Lombard, and collegues,

(2008).

1.2 Problem Statements

An air-cooled condenser is mostly used in the split type air conditioner.

Performance of the air cooled condenser depends on the ambient air temperature and

the thermal stability fluctuates throughout the year especially in hot weather. When

the ambient temperature increases thus, it will cause the pressure and temperature of

the air cooled condenser increases. This will force the compressor to work under

higher pressure ratio and consume more power. Sometimes the excessive pressure

can cause the compressor trip. The performance can be improved by raising the air

flow rate through the condenser coil but it will results in some noise problem. Luis

Perez- Lombard, and colleagues, (2008), reported that 17% of the total global energy

was consumed by air conditioning.

According to Chow, Lin and Yang, (2002), when the on-coil temperature of

condenser increase by 1˚C, the coefficient of performance of the system will

decrease by around 3%. It is because the refrigerant vapour state flowing through the

condenser coil unable to fully condense because of high ambient air temperature,

3

thus results in mixture of vapour and liquid refrigerant enters the expansion valve

(capillary tube) consequently decreasing the coefficient of performance of the system.

Whereas the experiment carried out by C. Chaktranond et al., (2010), reported that

electrical power consumption increases by 4% when the condenser temperature

increases every 1˚C.

1.3 Objectives of The Study

1.3.1 Main Objective:

To improve the performance of air-cooled condenser of split type air

conditioner.

1.3.2 Specific Objectives:

I. To reduce the temperature of ambient air by using cellulose evaporative

cooling pad before it passes over condenser coil.

II. To increase the coefficient of performance of the system by decreasing the

condenser on-coil temperature using indirect evaporative cooling method.

III. To reduce the energy consumption of the system by decreasing the

compressor work.

IV. To identify the relationship between ambient air temperature and COP of the

air conditioning system.

1.4 Work Scope of The Study

This experimental study mainly focused on the improvement on the

performance of an air cooled condenser of 1.5 horsepower split type air conditioning

4

system. Performance of air cooled condenser will be enhanced by decreasing the

ambient air temperature by placing corrugated cellulose evaporative cooling pad

injected with water at the upstream of the condenser. The ambient air temperature

before and after passes the cooling pad will be measured using thermocouple.

Next, comparing the coefficient of performance of the system with

evaporative cooling and without evaporative cooling system by measuring the high

side and low side pressure of the system using pressure gauge. The inlet and outlet

temperature of the major components such as compressor, condenser, expansion

valve and evaporator measured using thermocouple. Both temperature and pressure

data used to plot on the Mollier Chart and calculate the COP of the air conditioning

system with and without an evaporative cooling system. Also, compare the power

consumption of the air conditioning system with and without an evaporative cooling

system.

5

CHAPTER 2 LITERATURE REVIEW

2.1 Introduction

This chapter will be mainly focused on the literature review regarding the

enhancement of an air-cooled condenser of air conditioning and refrigeration systems.

Many experiments have been done by the researchers to improve the performance of

condenser by using several types of methods. There are some review related to the

project were done such as the evaporative cooler coupled with air-cooled condenser,

water mist system, direct evaporative cooling system, selection of evaporative

cooling pad and optimization of the evaporative cooling pad thickness, effect of

condenser air flow through the condenser coil, condenser fan performance and plain

and finned tube performance. By review the relevant literature, it will help the author

to understand the actual problem and able to conduct the experimental studies based

on the literature have been done.

2.2 Performance of Air-cooled Condenser

According to Xiaoli Hao et al., (2013), the air-cooled chillers have many

advantages over the water-cooled chillers such as no cooling tower and condenser

pump needed and also they never required any mechanical room for the chillers.

Although the air-cooled chillers have advantages over water-cooled chillers, but the

energy efficiency is less if compared to water-cooled chillers. Yu and Chan, (2005),

reported that the air-cooled condensers are constructed to working under condensing

temperature of 11-14 ˚C beyond the dry-bulb temperature of ambient air, whereas the

water-cooled condenser designed to working at a condensing temperature to be near

6

to 4-6 ˚C beyond the wet-bulb temperature of ambient air. Because of this, a greater

condenser pressure is needed by an air-cooled chillers compare to water-cooled

chillers, which influence to consume more power by the compressor and less

refrigeration capacity.

Thermal stability of an air-cooled condenser is based on the temperature of

ambient air and it is not stable throughout the year. Due to higher ambient air

temperature, the refrigerant flowing in the condenser coil unable to fully condense

and enters the expansion valve with the mixture of liquid and vapour thus, results in

decreasing of COP of the system. Tianwei Wang, Chenguang Sheng and Agwu

Nnanna, (2014). An experimental study by Chow et al., (2002), reported that 1˚C

increased on the on-coil temperature of the condenser results in decrease of COP of

the system by around 3%. To improve the COP of the system, the ambient air

temperature must decrease before it passes through the condenser coil.

2.3 Application of Evaporative Cooling for Air-cooled Condenser

Hajidavalloo, (2007), carried out an experiment to investigate the effect of

evaporative cooling for a window air conditioner using two methods. First, the

cellulose bound cardboard is used as an evaporative cooling pad and water is injected

on the cooling pad and by small water pump to provide cooling effect to the

condenser by evaporation of water. This method is known as indirect evaporative

cooling. Whereas, another method is direct evaporative cooling which means, water

is directly injected on the condenser coil. Although this method can increase the COP

of the system, there are some side effects such as mineral deposits and corrosion on

the condenser coil. By using the indirect evaporative cooling method, Hajidavalloo,

(2007), reported that about 16% of energy consumption decreased and at the same

time, about 55% increase in COP of the system.

Based on the experimental study of Goswami, Mathur and Kulkarni, (1993),

shows that the electric energy can be save up to 10% - 20% by using four

evaporative cooling pad around the condenser coil of an existing 2.5 ton air

conditioning system while the ambient air temperature is at 34˚C. Under local

7

condition, an indirect evaporative cooling system applied to packaged unit air

conditioner and they are able to improve the cooling load up to 75% and consume

55% less electrical energy. Delfani Shahram, (2010). Zhang et al., (2000), carried out

a study on the evaporative cooler permeated with corrugated holed aluminium foil

and given relationship to estimate the performance, pressure drop and outlet air

temperature of the cooler. They apply the relationship for estimate the enhancement

of an air-cooled chiller by analyze the exit temperature of evaporative cooler with the

performance curve of the chiller and conclude that the COP for chiller could be

enhanced about 39%. An air-cooled chiller coupled with a direct evaporative cooler

able to reduce 14.4% in power consumption and increase the refrigeration capacity

about 4.6%. Yu and Chan, (2005).

Chaktranond and Doungsong, (2010), carried out an experimental study on the

residential size split type air conditioner’s condensing unit retrofitted with an indirect

evaporative cooling system. The water injecting method on the evaporative cooling

pad divided into two types which is water curtain and water spray. The evaporative

cooling pad is placed in the upstream flow of air entering the condenser coil. The gap

between the condenser coil and the evaporative cooling pad is 0.05m. By using this

indirect evaporative cooling system, the ambient air temperature that entering the

condenser coil could be reduced up to 3˚C and conclude that the ambient air

temperature affects the system performances more than the relative humidity.

Figure 2.1: Schematic diagram of evaporative cooling system (Chaktranond and Doungsong, 2010)

8

2.4 Water Spray Mist Pre-Cooling System

According Hsieh and Yao, (2006), the water spray mist cooling system with a

tor or mesh material (WSMCST) is not a new concept because it have been applied

in various types of industries, but not common in air conditioning and refrigeration

system. This condenser performance enhancement method is differing from other

method due to this system monitored in real-time and electronically controlled. This

WSMCST system mainly consists of three subsystems such as water treatment and

control unit, high pressure pulverization unit with atomization nozzles and the third

is a specially manufactured microprocessor. An experimental study by Jia Yang et al.,

(2012), shows that the high pressure pump deliver water with 70 bar pressure and

forced through a micro nozzle to create a mist of 10µm droplets to produce a cloud

of very small water droplets. These droplets vaporized by the ambient air before get

in the condenser coil and the ambient air temperature reduced follow by the adiabatic

cooling process with constant specific enthalpy.

Jia Yang et al., (2012), reported that, this system does not cause any flow

obstructions to the air stream of the air-cooled condenser. It uses only a little amount

of electric energy to run the high pressure pump to form water mist. According to

Pongsakorn and Thepa, (2013), a study on the inverter air conditioning system tested

under multiple water spray rates and frequencies with three different temperature

scales in fixed ambient temperature. This study results in increase of COP by 35% at

a lower water spray rate of 100 L/h and a higher frequency of 80-90 Hz. Yu and

Chan, (2005), noticed that there is not enough research on the chillers which using

multiple compressors and good water mist generation under condenser temperature

control (CTC), the characteristic of dry-bulb temperature (DBT) and relative

humidity (%RH) of the ambient air which get in the condenser coil is the important

parameters to evaluate the thermal effectiveness of the water mist system.

9

Figure 2.2: Schematic of the air-cooled chiller with water mist system (Jia Yang et al., 2012)

2.5 Direct Evaporative Cooling (DEC) System

Based on Camargo et al., (2005), induced processes of mass and heat transfer

by using the water and air as working fluids is the working principal of evaporative

cooling. It comprises, particularly, in evaporation of water, impelled by the transition

of an air flow, thus results in lowering the temperature of the air. At the point water

evaporates into the air, its temperature dropped down and consequently humidifying

the air, this thermal process is called the adiabatic saturation and also known as the

direct evaporative cooling (DEC). Ebinuma et al., (2002), study the operation

principal of direct and indirect evaporative cooling systems by the development of

mathematical equations of thermal exchanges, which allow finding the heat transfer

convection coefficient for primary and secondary air flow.

Dai and Sumathy et al., (2002), carried out an investigation on a cross-flow direct

evaporative cooler to optimize the length of air channel in order to enhance the

performance of the wet honeycomb paper constitutes packing material.