Cooling Load Estimate, Psychrometry, Air Handling Equipment Selection And Air Duct Design For The Dx Air Conditioning System Of An Office Block

The design of an air conditioner within an HVAC system is dependent on the specific project requirements, as well as the designer’s approach to design, experience level, knowledge of code-driven requirements and standard practices, and the ability to communicate the design intent clearly through the preparation of plans and specifications.

While an air conditioner is an important part of a building’s HVAC system, the entire system should be considered during a complete design. Such factors are cooling load estimate, psychrometry, air handling equipment selection and air duct design for the direct expansion air conditioning system. These factors are discussed in this work.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

1.0      INTRODUCTION

1.1      BACKGROUND OF THE STUDY

• OBJECTIVE OF THE STUDY
• SIGNIFICANCE OF THE STUDY
• SCOPE OF THE STUDY
• ADVANTAGES OF DIRECT EXPANSION SYSTEM
• PURPOSE OF THE STUDY

CHAPTER TWO

LITERATURE REVIEW

• OVERVIEW OF THE STUDY
• OPERATING PRINCIPLES
• OVERVIEW OF INSTALLATION TYPES OF AIR CONDITIONER SYSTEM
• OVEVIEW OF DIRECT EXPANSION (DX) TYPE OF CENTRAL AIR CONDITIONING

CHAPTER THREE

3.0     CONSTRUCTION METHODOLOGY

3.1      COOLING LOAD ESTIMATE

3.2     AIR CONDITIONING PSYCHROMETRICS

3.3      MEASURING PSYCHROMETRIC VARIABLES

3.4      AIR HANDLING UNIT SELECTION

3.5      AIR DUCT DESIGN FOR DX AIR CONDITIONER SYSTEM

CHAPTER FOUR

• DUCTWORK TESTING AND SYSTEM PERFORMANCE
• TESTING METHODS AND EQUIPMENT
• AIR FLOW MEASUREMENT INSTRUMENTS
• DETERMINING AIR FLOW IN DUCTS
• PROVISIONS DURING DESIGN FOR TESTING, ADJUSTING AND BALANCING
• DUCT CLEANING
• STANDARD EQUATIONS IN AIR-CONDITIONING
• CONCLUSION

CHAPTER FIVE

• CONCLUSION
• REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION

Air conditioning is the process of removing heat and moisture from the interior of an occupied space, to improve the comfort of occupants. Air conditioning can be used in both domestic and commercial environments. This process is most commonly used to achieve a more comfortable interior environment, typically for humans and animals; however, air conditioning is also used to cool/dehumidify rooms filled with heat-producing electronic devices, such as computer servers, power amplifiers, and even to display and store some delicate products, such as artwork [4].

Air conditioners often use a fan to distribute the conditioned air to an occupied space such as a building or a car to improve thermal comfort and indoor air quality. Electric refrigerant-based AC units range from small units that can cool a small bedroom, which can be carried by a single adult, to massive units installed on the roof of office towers that can cool an entire building. The cooling is typically achieved through a refrigeration cycle, but sometimes evaporation or free cooling is used. Air conditioning systems can also be made based on desiccants (chemicals which remove moisture from the air) and subterraneous pipes that can distribute the heated refrigerant to the ground for cooling [5].

In the most general sense, air conditioning can refer to any form of technology that modifies the condition of air (heating, (de-)humidification, cooling, cleaning, ventilation, or air movement). In common usage, though, “air conditioning” refers to systems which cool air. In construction, a complete system of heating, ventilation, and air conditioning is referred to as HVAC [3].

The main function of an air conditioning system is mainly to produce cool ventilation inside the building in which the heat is taken out from a certain location to give a chilled air effect. The main process is that the air circulation is drawn to the condenser containing refrigerant gas.

There are four major types of air conditioner like Window, Split, Packaged and Central. In this work we are looking at direct expansion (DX) type of air conditioner which is among the two types of central air conditioner [6].

In the DX system the air used for cooling the room or space is directly passed over the cooling coil of the refrigeration plant. The direct expansion system in HVAC has been growing rapidly due to its ability to get rid of most duct work and piping. The popularity of this system is because the installation work has been made easier hence reducing the cost of the overall system.

The DX System works in such a way that the evaporator is located in the space to be refrigerated. When the refrigerant in the evaporator coil expanded, it will cool the space by absorbing the heat from it.

However, In designing air Direct Expansion (DX) systems, there are some factors that the designer need to which can be a challenge and later affect the building. Such factor are: Cooling load estimate, psychrometry, air handling equipment selection and air duct design for the DX air conditioning system. The aim of this study is to discuss this design factor for Direct Expansion (DX) systems [7].

1.1                                              OBJECTIVES OF THE STUDY

At the end of this work, the student carrying out this project shall be able to:

1. study and understand these four factor
2. calculate and determine this factors using proved formulas

• fully discuss the various refrigerants that can be found in air conditioning systems

1. Learn about the details of HVAC system installation, including the placement of compressor and condenser units.

1.2                                           SIGNIFICANCE OF THE STUDY

This study has the following advantages:

1. is used in analysis of an air-conditioning system in order to determine the volume flow rates of air to be pushed into the ducting system and the sizing of the major system components
2. it also used to understand the components that affect the building heat gain or heat loss – this process is called heating or cooling load estimation.

• It is used to determine the volume flow rates of air to be pushed into the ducting system and the sizing of the major system

1.3                                                   SCOPE OF THE STUDY

HVAC stands for Heating, Ventilation, and Air Conditioning. This is the building system that regulates the inside temperature of the building and, in some systems, the air quality as well. The principles of HVAC design include the basic theory of system operation and the factors that determine the size and capacity of the equipment installed in the system. The study of Cooling load estimate, psychrometry, air handling equipment selection and air duct design gives us the understanding of the basics for the DX air conditioning system design [4].

1.4                                                                                                                                                                                             ADVANTAGES OF DIRECT EXPANSION SYSTEM

1. Low installation costs.
2. Ease to test, adjust and balance the system.

• Minimum ceiling or wall space needed.

1. Low energy consumption.
2. Low maintenance costs.
3. Individual section can be operated without running the entire system in the building.

• Comfort under varying load conditions.
• Low noise level (NC 35).

1. Good relative humidity control.

1.5                                              PURPOSE OF THE STUDY

The main purpose of this paper is make proper calculation of cooling load, supply air quantity using proper method , decide size of main duct and elbow using proper duct design method so person seating in the office can feel comfortable .