REFRIGERATION STUDY FOR DOMESTIC APPLICATION

ANIZAN BIN WAN RAMLI

A report submitted in partial fulfillment of the requirements for the award of the degree Bachelor of Mechanical Engineering

Faculty of Mechanical EngineeringUNIVERSITI MALAYSIA PAHANG

NOVEMBER 2008

ii

SUPERVISOR’S DECLARATION

We hereby declare that we have checked this project and in our opinion this project is

satisfactory in terms of scope and quality for the award of the degree of Bachelor of

Mechanical Engineering

Signature : ..........................................

Name of Supervisor: Mohd Yusof bin Taib

Position : Lecturer

Date : ..........................................

Signature : ...........................................

Name of Panel : ...........................................

Position : ...........................................

Date : ...........................................

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STUDENT’S DECLARATION

I hereby declare that the work in this thesis is my own except for quotations and

summaries which have been duly acknowledged. The thesis has not been accepted for

any degree and is not concurrently submitted for award of other degree.

Signature : .................................................

Name : Anizan bin Wan Ramli

ID Number: MA05030

Date : .................................................

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To my beloved father and mother,

Mr Wan Ramli bin Wan Abdul Rahman

Mdm Jariah binti Mohamad

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ACKNOWLEDGEMENTS

Alhamdulillah, I would like to take this opportunity to express my deepest

gratitude to Allah because of His willingness to give strength and will for me to finish

this project successfully. First and foremost, many warm thanks to my supervisor Mr

Yusof bin Taib for his constant help, support and guidance which has steered me to

finish my project. His enthusiasm and professional works has motivated me whenever I

feel down while doing my project. Whenever I really need help, he always provide me

with his help and ideas which helped me overcome the difficulties in doing my project. I

am very grateful for his willing helping me without asking for a repay

My sincere thanks go to all my friends, the staff of the Mechanical Engineering

Department, UMP, who helped me in many ways and made my stay at UMP pleasant

and unforgettable. Many special thanks go to my colleagues in M16, M17, M20, M23

and all mechanical students in UMP for their excellent co-operation, inspirations and

supports during this study.

I acknowledge my sincere indebtedness and gratitude to my parents for their

love, dream and sacrifice throughout my life. I cannot find the appropriate words that

could properly describe my appreciation for their devotion, support and faith in my

ability to attain my goals. Special thanks should be given to my committee members. I

would like to acknowledge their comments and suggestions, which was crucial for the

successful completion of this study.

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ABSTRACT

Refrigeration, cooling, and heating processes are important in a variety of everyday

situations, including the air conditioning and heating of buildings, and in a treatment,

transportation, and preservation of foods and beverages. Refrigeration also finds large

scale industrial application, for example, in the manufacture of ice and the dehydration

of gases. This paper gives an understanding of refrigeration study for domestic

application. By learning and understanding the basic vapour-compression refrigeration

systems, the performance of refrigeration system expected can be determined using

refrigerator test rig. The literature study has been conducted by two important

parameters in order to analyze performance of the refrigerator. These parameters are

pressure and temperature. The literature study is crucial at the location of parameter on

the test rig that will be develop. This paper also describes procedure to fabricate the test

rig. Then, the refrigerator test rig will test in order to analyse the performance of the

refrigerator test rig. The performance of the refrigerator test rig analyse by the using the

actual pressure-enthalpy diagram of actual refrigeration cycle and by using the equation.

This study may help the audience to analyze the actual performance of the refrigerator

performance for domestic application.

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ABSTRAK

Penyejukan, pendinginana dan pemanasan adalah proses yang penting dalam pelbagai

situasi setiap hari, termasuklah penghawa dingin dan pemanasan bangunan dan dalam

rawatan, pengangkutan dan pengekalan kualiti makanan dan minuman. Penyejukan

digunakan secara meluas dalam aplikasi perindustrian, contohnya dalam pembuatan ais

dan dehidrasi gas. Kertas kerja ini memberi pemahaman dalam kajian untuk penggunaan

domestik. Melalui pembelajaran dan pemahaman asas kemampatan wap sistem

penyejukan, kecekapan sistem penyejukan yang dijangka boleh ditentukan

menggunakan pegendali ujian peti ais. Kajian kesusasteraan telah dibimbing oleh dua

parameter penting dalam mengkaji kecekapan sesbuah peti ais. Parameter-parameter

tersebut adalah tekanan dan suhu. Kajian kesusasteraan genting di lokasi parameter pada

pengendali ujian peti ais yang akan dibuat. Kertas kerja ini juga menghuraikan prosedur

untuk membuat the pegendali ujian. Kemudian, pengendali ujian peti ais akan diuji

untuk analisis kecekapan pengendali ujian peti ais tersebut. Kecekapan pengendali ujian

peti sejuk dianalisis menggunakan gambar rajah tekanan-entalpi sebenar bagi putaran

penyejukan dan menggunakan persamaan. Kajian ini dapat membantu masyarakat untuk

analisis kecekapan sebenar bagi sesebuah peti ais untuk aplikasi domestik.

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TABLE OF CONTENTS

Page

SUPERVISOR’S DECLARATION ii

STUDENT’S DECLARATION iii

DEDICATION iv

ACKNOWLEDGEMENTS v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENTS viii

LIST OF TABLES xi

LIST OF FIGURES xii

LIST OF SYMBOLS xiv

LIST OF ABBREVIATIONS xv

CHAPTER 1 INTRODUCTION

1.1 Introduction 1

1.3 Problem Statement 4

1.3 Objectives of the Research 7

1.4 Overview of the Thesis 8

CHAPTER 2 LITERATURE REVIEW

2.1 Introduction 10

2.2 Refrigeration System 10

2.2.1 Components of Refrigerator System 10 2.2.2 Theory of Refrigeration Cycle 11

ix

2.2.3 Refrigerant Effect2.2.4.....Heat Rejection In a Condenser2.2.5.....Mass of Flow Rate2.2.6.....Compressor Power2.2.7.....Coefficient of Performance (COP)

14

2.3 Development Reviews of Refrigerator Test Rig 21

2.4 Measurement Method

2.4.1.....Temperature Measurement2.4.2.....Pressure Measurement

34

CHAPTER 3 METHODOLOGY

3.1 Introduction 35

3.2 Flow Chart 36

3.2.1 Material information 39 3.2.2 Loading information 393.4 FE based Fatigue Analysis Process 48

3.5 FE Analysis Techniques 48

3.6 Conclusions 52

CHAPTER 4 RESULTS AND DISCUSSION

4.1 Introduction 53

4.2 Results of Experimental Rig 53

4.2.1 Construct P-h Diagram 534.2.2 Enthalpy Value

4.2.3.....Refrigerant Effect Analysis

61

4.3 Validation 66

4.4 Duability Assessment 73

4.5 Conclusions 74

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CHAPTER 5 CONCLUSION AND RECOMMENDATIONS

5.1 Introduction 75

5.2 Conclusions 75

5.2.1 Finite element modeling 765.2.2 Fatigue life predictions 77

5.3 Recommendations for the Future Research 80

REFERENCES 81

APPENDICES 91

A Components of Combustion Side 91

B Components of Kickback Side 93

C List of Publications 95

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LIST OF TABLES

TABLE NO TITLE PAGE

3.1 Technical specification of the refrigerator model URF-M50A 30

4.1 Enthalpy value for each measurement point 33

4.2 Result of refrigerating effect 34

4.3 Results of heat rejection in a condenser 36

4.4 Results of Work of compressor 37

4.5 Results of mass flow rate 39

4.6 Results of compression power 41

4.7 Results of refrigerant capacity 43

4.8 Results of heating capacity 44

4.9 Results of Coefficient of performance (COP) 46

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LIST OF FIGURES

FIGURE NO TITLE PAGE

2.1 Refrigeration cycle shown schematically and graphically 5

2.2 Cutaway of reciprocating compressor 7

2.3(a) The process path on a pressure-enthalpy (P-h) diagram 9

2.3(b) Schematic diagram of the process equipment 9

2.4 Ideal T-s diagram of refrigerator system 10

2.5(a) Actual P-h diagram 11

2.5(b) Actual T-s diagram 11

2.6 Schematic diagram transducers line in refrigerator system 14

2.7 Schematic diagram of the test facility with the main instrumentation

points. 15

2.8 Bourdon low pressure gauge 17

3.1 Photograph URF-M50A refrigerator model 18

3.2 Flow chart of Final Year Project 19

3.3 The schematic diagram of the test unit and apparatus 21

3.4 The refrigerator test unit 21

3.5 A flare fitting and flare nut for tubing connection 22

3.6 Screw-type flaring tool 22

3.7 The fitting for soldering or brazing 24

3.8 Construction method of temperature measurement point 25

3.9 Construction temperature measurement point 26

3.10 Assembly method of pressure measurement using pressure gauge 27

4.1 Graph of refrigerating effect (kJ/kg) versus time (min) 35

4.2 Graph of heat rejection in condenser (kJ/kg) versus time (min) 36

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4.3 Graph of work of compressor (kJ/kg) versus time (min) 38

4.4 Graph of mass flow rate (kg/s) versus time (min) 40

4.5 Graph of compressor power (kJ/s) versus time (min) 41

4.6 Graph of refrigerant capacity (W) versus time (min) 43

4.7 Graph of heating capacity (kJ/s) versus time (min) 44

4.8 Graph of COP versus time (min) 45

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LIST OF SYMBOLS

Mass flow rate

Refrigeration capacity

Heating capacity

Heat rejection in a condenser

Refrigerant effect

P Pressure

V Volume

R Gas constant value

T Temperature

P Compressor power

W Work done

h Enthalpy value

Wcomp Work of compressor

V Voltage

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LIST OF ABBREVIATIONS

ANSI American National Standards Institute

ARI Air Conditioning and Refrigeration Institute

ASHRAE American Society of Heating, Refrigeration, Air Conditioning Engineers

COP Coefficient of Performance

UMP Universiti Malaysia Pahang

1

CHAPTER 1

INTRODUCTION

1.1 The Domestic Refrigerator

Refrigeration is widely used in variety of thermal engineering applications.

Refrigeration is defined as the process of removal of heat from an enclosed space, or

from a substance, and rejecting it elsewhere for the primary purpose of lowering the

temperature of the enclosed space or substance and then maintaining that lower

temperature. The refrigeration system actually based on a vapor-compression cycle

which consisting four main components; a compressor, a condenser, a capillary tube or

expansion valve and an evaporator. The working fluid that used in the refrigeration

system is R-134a. The first patent of a vapor-compression refrigeration system was

obtained by American inventor named Jacob Perkins in 1834.

The cycle of vapor-compression of refrigeration start when the refrigerant enters

the compressor at high pressure of superheated vapor and it’s compressed isentropically

to the condenser pressure. Then, the refrigerant enters the condenser as superheated

vapor and leaves as saturated liquid as a result of heat rejecting to the surroundings. The

saturated liquid refrigerant is throttled to the evaporator pressure by passing it through

an expansion valve or capillary tube. During this process, the temperature of the

refrigerant drops below the temperature of the refrigerate space. Then, the refrigerant

enters the evaporator as a low-quality saturated mixture, and it completely evaporates by

absorbing heat from the refrigerated space. The cycle is complete as the refrigerant

leaves the evaporator and re-enters the compressor.

2

This report gives an understanding of refrigeration study for domestic

application. By learning and understanding the basic vapor-compression refrigeration

systems, the performance of refrigeration system expected can be determined. The test

rig will be develop in order to analyze the performance of refrigerator. The author has

conducted literature study in identify parameter to analyze the refrigerator performance.

The literature study is crucial at the location of parameter on the test rig that will be

developed. Based on the literature study, a test rig is being developed according to the

international standard for tropical climate such as ASHRAE, AHAM and ARI to

generate the refrigerator performance.

1.2 Problem Statement

Nowadays, refrigeration system is important in a wide variety used for domestic

application. However, the actual performance of the refrigerator still unknown. So, we

need some research to analyze the actual performance of refrigerator.

1.3 Objective of Research

The main objective of this study is to develop experimental rig for refrigeration

system and to determine the coefficient of performance (COP) of the refrigeration

system.

1.4 Scope

The scopes of this study are:

1) Literature Study

The literature study is focused how to identify the strategic and suitable locations

of pressure and temperature measurement.

3

2) Thermodynamics analysis

By learning and understanding the basic vapor compression refrigeration

systems, the performance of refrigeration system can be determined.

3) Test Rig development

In order to analyze performance of the refrigeration system, the test rig needs to

be developed. There are two important of parameters in the rig development

works which are location and measurement method of pressure and temperature.

4) Testing and analysis

Analyze the data by using P-h diagram and second law of thermodynamic to

determine the coefficient of performance (COP) of the system.

4

CHAPTER 2

LITERATURE REVIEWS

2.1 Introduction

This chapter discusses the relevant reports on the description of refrigeration

system, components that is installed in domestic refrigerators, measurement method and

development reviews of refrigerator test rig. These reviews are important to analysis the

performance of refrigerator system in domestic application.

2.2 Refrigeration System

Currently, there are many types of refrigeration system available in the market.

Those refrigerators are classified according to their application. The most popular type

of domestic refrigeration system is called refrigerator. Normally, this type of

refrigeration system consists of two compartments which are cold and freeze

compartments. The other types of refrigerator systems are freezer and cooler. The

primary function of a refrigerator or freezer is to provide food storage space maintained

at a low temperature for the preservation of food. Mechanical vapor compression cycle

as well as the absorption cycle, are adopted for domestic refrigerators and freezer.

Refrigeration is defined id the process of removal of heat from an enclosed space, or

from substance, and rejecting it elsewhere for the primary purpose of lowering the

temperature of the enclosed space or substance and then maintaining that lower

temperature. The refrigeration system is that based on a vapor compression cycle which

consisting four main components; a compressor, a condenser, a capillary tube or

expansion valve and evaporator as shown in Figure 2.1

5

Surrounding T

Evaporator

Capillary QH 2 Tube Compressor 3 Wcomp

Wcomp

Condenser QL

4 1 s

Refrigerated Space

(a) Refrigerator plant (b) Ideal T-s diagram of refrigeration plant

Figure 2.1: Refrigeration cycle shown schematically and graphically

2.2.1 Components of Refrigerator System

There are several mechanical components required in a refrigerator system.

Basically, there are four major components of vapor-compression refrigeration system.

These components are compressor, condenser, capillary tube and evaporator [2].

2.2.1.1 Compressor

In a refrigeration cycle, the compressor has two main functions within the

refrigeration cycle. The function of the compressor is to pump the refrigerant vapor from

the evaporator so that the desired temperature and pressure of the system. The second

function is to increase the pressure of the refrigerant vapor through the process of

compression, and simultaneously increase the temperature of refrigerant vapor [3]. The

pressure of the refrigerant vapor leaving the evaporator must be elevated (or the vapor

has to be compressed) to the level of the condensing pressure, so that the refrigerant can

be condensed into a liquid in the condenser and fed to the evaporator for the continuous

refrigeration [4].

6

The most common compressor used in domestic refrigeration is reciprocating

type. This type of compressor normally constructed with pistons, cylinders, valves,

connecting rods and crankshaft as shown in Figure 2.2. The function of each main

component that commonly used in reciprocating compressor are described below:

Piston head – functions as the gas compressing “agent” by continuously reducing

the cylinder volume

Piston rings – functions as the sealant between the piston head, and the cylinder,

to prevent gas leakage from the compression chamber

Crank shaft – a shaft that enables the reciprocating motion of the piston

Piston rod – the connecting piece between the piston head, and the crankshaft

Spring loaded suction and discharge valves – separates low pressure side and

high pressure side from the compression chamber. Enables positive displacement

of gases, by correct opening and closing of the valves. Suction valve will open as

the piston moves away from the valves, and discharge valve will open as the

piston moves towards the valves. The valves will otherwise, be in closed

position. The suction and discharge valve are usually a thin plate or reed that will

open and close easily and quickly [3].

Compressor’s cylinder block – functions as the housing for the compressor parts

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Figure 2.2: Cutaway of reciprocating compressor

2.2.1.2 Condenser

The heat extracted from the substance to be cooled by the refrigerant in the

evaporator is rejected to the atmosphere through the condenser. There are several types

of condensers that commonly used in refrigeration system. They are air-cooled, water-

cooled, shell and tube, shell and coil, tube within a tube, and evaporative condensers [3].

However, most of domestic refrigerators are used evaporative condenser. The refrigerant

is forced through the condenser. In order to remove as much heat as possible with the

tubes arranged to provide maximize surface area. In the condenser, the temperature of

the superheated vapor has to be brought down to its saturation temperature before

condensed into a liquid. The first few tubes of the condenser ‘desuperheat’ the vapor.

The pressure of the vapor, through superheated, remains the same, since the compressor

is in operation. Once the vapor has been cooled, and brought down to the condensing

temperature corresponding to the head pressure, the vapor begins to condense. During

this process, the pressure and condensing temperature remain constant. In some water-

cooled condensers, provision is made for sub-cooling the liquid from its saturation

temperature by providing some water tubes at the bottom. The liquid can be sub-cooled

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by the use of a liquid-suction heat exchanger also. The use of heat exchanger, obviously,

will increase the superheat of the suction vapor. As too much superheating of the suction

vapor will affect the compressor capacity, a heat exchanger is only used where

absolutely essential [12].

2.2.1.3 Capillary Tube

The capillary tube is the simplest type of refrigerant flow control device and may

be used in place of an expansion valve. The capillary tube is small-diameter tubes

through which the refrigerant flows into the evaporator. These devices, which are widely

used in small hermetic-type refrigeration system, reduce the condensing pressure to the

evaporating pressure in a copper tube of small internal diameter, maintaining a constant

evaporating pressure independently of the refrigeration load range. These tubes are used

to transmit pressure from the sensing bulb of some temperature control device to the

operating element. A capillary tube may also be constructed as a part of heat exchanger,

particularly in household refrigerators [5, 6].

2.2.1.4 Evaporator

Evaporator can be considered the point of heat capture in refrigeration system

and provides the cooling effect required for any particular application. In evaporator

operation, the metering device changes the entering liquid to a dense fog of liquid

droplets. During the same process, the high pressure liquid is lowered to what is called

the evaporator pressure, or suction pressure. This pressure relates to the evaporator

temperature. During evaporation, the refrigerant remains the same temperature (its

saturation temperature) throughout the coil until all droplets of liquid are vaporized, or

totally saturated.

Meanwhile, the refrigerant nears the end of evaporator part is in fully saturated

vapor that can only absorb sensible heat; however it does not contribute much to the

overall refrigeration performance.

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2.2.2 Theory of Refrigeration Cycle

Commonly, refrigeration system works in a thermodynamic cycle which obeys

Second Law of Thermodynamic which consists of four thermodynamic processes

involving the working fluid, traversing four fluid states at low temperature, Tlow and high

temperature, Thigh [1] and [2] as shown in Figure 2.3:

Figure 2.3: (a) Shows the process path on a pressure–enthalpy (P– h) diagram, and (b)

shows a schematic diagram of the process equipment.

The cycle of refrigeration start when the refrigerant enters the compressor at low-

pressure superheated vapor and is compressed isentropically to the condenser pressure.

The refrigerant enters the condenser as superheated vapor and leaves as saturated liquid

as a result of heat rejecting to the surroundings. The saturated liquid refrigerant is

throttled to the evaporator pressure by passing it through an expansion valve or capillary

tube. During this process, the temperature of the refrigerant drops below the temperature

of the refrigerant space. Then, the refrigerant enters the evaporator as a low-quality

saturated mixture, and it completely evaporates by absorbing heat from the refrigerated

space. The cycle is complete as the refrigerant leaves the evaporator and re-enters the

compressor.