A Mini Project Report

ON

A/C SYSTEM OF AN AUTOMOBILE

[A Dissertation report submitted in the partial fulfillment of the academic requirement for the award of degree in Bachelor of Technology]

In

MECHANICAL ENGINEERING

By

ABUZAR SIDDIQUIE (07E21A0301) SANTOSH KUMAR SWAIN (07E21A0341)

Under the guidance ofAsst Prof. Layeeq Ahmed

DEPARTMENT OF

MECHANICAL ENGINEERING

VIDYA VIKAS INSTITUTE OF TECHNOLOGY

[AFFILIATED TO JAWAHARLAL NEHRU TECHNOLOGICA UNIVERSITY][SURVEY NO: 103&104, CHEVELLA, RANGA REDDY DIST.—501 503]

2010-2011

VIDYA VIKAS INSTITUTE OF TECHNOLOGY

[AFFILIATED TO JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY RECOGNISED BY AICTE]

SURVEY NO: 103&104, CHEVELLA, RANGA REDDY DIST.—501 503

CERTIFICATE

This is to certify that the seminar work entitled “A/C SYSTEM OF AN

AUTOMOBILE” that is being submitted by

ABUZAR SIDDIQUIE (07E21A0301) SANTOSH KUMAR SWAIN (07E21A0341)

In partial fulfillment for the award of the degree of mechanical Engineering by

Jawaharlal Nehru Technological University, Hyderabad is bona-fide work carried

out by them during the academic year 2010-2011.

Asst Prof. Laeeq Ahmed Dr. SYED YOUSUFUDDININTERNAL GUIDE HEAD OF THE DEPARTMENT

Dr. A. GANGADHAR PRINCIPAL EXTERNAL EXAMINAR

DECLARATION

We hereby declare that the project entitled submitted to the department of Mechanical Engineering, Vidya Vikas Institute of Technology affiliated to the Jawaharlal Nehru Technological University, Hyderabad for partial fulfillment of the requirement for the award of Bachelor of Technology in mechanical engineering of original work carried out by us. This work in original has not been submitted so far in part or full for any other institute or university.

ACKNOWLEDGEMENT

We thanks to almighty for giving us the courage& perseverance in completing the project. This project itself is an acknowledgement for all those who have given us their heart-felt-co-operation in making it a grand success. We are thankful to our principle,Dr.A.GANGADHAR for providing the necessary infrastructure and labs. We are greatly indebted to, Head of Mechanical Engineering, Mr.MD.YOUSUFUDDIN for providing valuable guidance at every stage of this project work. We also thankful to the project coordinator, prof.RAFIUZZAMA SHAIK for extending their sincere & heartfelt guidance throughout this project work. Without their supervision and many hours of devoted guidance, stimulating & constructive criticism, this thesis would never come out in this form. It is a pleasure to express our deep and sincere gratitude to the project guide, Mr.TAJMUL HUSSAIN ad are profoundly grateful towards the unmatched help rendered by him. Our special thanks to all the lectures of Mechanical Engineering, for their valuable advices at very stage of this work. Last but not the least: we would like to express our deep sense and earnest thanks giving to our dear parents for their moral support and heartfelt cooperation in doing the project. We would also like to thank our friends, whose direct or indirect help has enabled us to complete this work successfully.

CONTENTS

History

Air conditioning

Refrigerant

Air conditioning application

Humidity control

Health implication

Automobile air conditioners

Portable air conditioners

Working of an air conditioners

Heat pumps

Heat pump theory

The law of thermodynamics

The zeroth law of thermodynamics

The first law of thermodynamics

The temperature pressure relationship

A\c evaporators

Evaporator core

working of air conditioning evaporator

compressor

Working of an air compressor

Types of air compressor

Reciprocating air compressor

Rotary air compressor

Centrifugal air compressor

Working of different compressors

Reciprocating compressors

Rotary compressors

Screw compressors

Centrifugal compressors

Scroll compressors

Pressure regulating devices

Orifice tube

Thermal expansion valve

Receiver-Drier

Accumulator

Conclusion

History

The 2nd century Chinese inventor Ding Huan (fl. 180) of the Han Dynasty invented a rotary fan for air conditioning, with seven wheels 3 m (9.8 ft) in diameter and manually powered. In 747, Emperor Xuanzong (r. 712–762) of the Tang Dynasty (618–907) had the Cool Hall (Liang Tian) built in the imperial palace, which the Tang Yulin describes as having water-powered fan wheels for air conditioning as well as rising jet streams of water from fountains. During the subsequent Song Dynasty (960–1279), written sources mentioned the air conditioning rotary fan as even more widely used.

Medieval Persia had buildings that used cisterns and wind towers to cool buildings during the hot season: cisterns (large open pools in central courtyards, not underground tanks) collected rain water; wind towers had windows that could catch wind and internal vanes to direct the airflow down into the building, usually over the cistern and out through a downwind cooling tower. Cistern water evaporated, cooling the air in the building. Wind catchers were widely used throughout the medieval Muslim world, where they were used for air conditioning in many cities.

Ventilators were invented in medieval Egypt and were widely used in many houses throughout Cairo during the Middle Ages. These ventilators were later described in detail by Abd al-Latif al-Baghdadi in 1200, who reported that almost every house in Cairo had a ventilator, and that they cost anywhere from 1 to 500 dinars depending on their sizes and shapes. Most ventilators in the city were oriented towards the Qibla, as was the city in general.

In the 1600s Cornelius Drebbel demonstrated "turning Summer into Winter" for James I of England by adding salt to water.

In 1758, Benjamin Franklin and John Hadley, a chemistry professor at Cambridge University, conducted an experiment to explore the principle of evaporation as a means to rapidly cool an object. Franklin and Hadley confirmed that evaporation of highly volatile liquids such as alcohol and ether could be used to drive down the temperature of an object past the freezing point of water. They conducted their experiment with the bulb of a mercury thermometer as their object and with a bellows used to "quicken" the evaporation; they lowered the temperature of the thermometer bulb down to 7°F while the ambient temperature was 65°F. Franklin noted that soon after they passed the freezing point of water (32°F) a thin film of ice formed on the surface of the thermometer's bulb and that the ice mass was about a quarter inch thick when they stopped the experiment upon reaching 7°F. Franklin concluded, "From this experiment, one may see the possibility of freezing a man to death on a warm summer's day".

In 1820, British scientist and inventor Michael Faraday discovered that compressing and liquefying ammonia could chill air when the liquefied ammonia was allowed to evaporate. In 1842, Florida physician John Gorrie used compressor technology to create ice, which he used to cool air for his patients in his hospital in Apalachicola, Florida. He hoped eventually to use his ice-making machine to regulate the temperature of buildings. He even envisioned centralized air conditioning that could cool entire cities. Though his prototype leaked and performed irregularly, Gorrie was granted a patent in 1851 for his ice-making machine. His hopes for its success vanished soon afterwards when his chief financial backer died; Gorrie did not get the money he needed to develop the machine. According to his biographer, Vivian M. Sherlock, he blamed the "Ice King", Frederic Tudor, for his failure, suspecting that Tudor had launched a smear campaign against his invention. Dr. Gorrie died impoverished in 1855 and the idea of air conditioning faded away for 50 years.

In 1902, the first modern electrical air conditioning unit was invented by Willis Haviland Carrier in Buffalo, New York. After graduating from Cornell University, Carrier, a native of Angola, New York, found a job at the Buffalo Forge Company. While there, Carrier began experimentation with air conditioning as a way to solve an application problem for the Sackett-Wilhelms Lithographing and Publishing Company in Brooklyn, New York, and the first "air conditioner," designed and built in Buffalo by Carrier, began working on 17 July 1902.

Designed to improve manufacturing process control in a printing plant, Carrier's invention controlled not only temperature but also humidity. Carrier used his knowledge of the heating of objects with steam and reversed the process. Instead of sending air through hot coils, he sent it through cold coils (ones filled with cold water). The air blowing over the cold coils cooled the air, and one could thereby control the amount of moisture the colder air could hold. In turn, the humidity in the room could be controlled. The low heat and humidity were to help maintain consistent paper dimensions and ink alignment. Later, Carrier's technology was applied to increase productivity in the workplace, and The Carrier Air Conditioning Company of America was formed to meet rising demand. Over time, air conditioning came to be used to improve comfort in homes and automobiles as well. Residential sales expanded dramatically in the 1950s.

In 1906, Stuart W. Cramer of Charlotte, North Carolina was exploring ways to add moisture to the air in his textile mill. Cramer coined the term "air conditioning", using it in a patent claim he filed that year as an analogue to "water conditioning", then a well-

known process for making textiles easier to process. He combined moisture with ventilation to "condition" and changes the air in the factories, controlling the humidity so

necessary in textile plants. Willis Carrier adopted the term and incorporated it into the name of his company. This evaporation of water in air, to provide a cooling effect, is now

known as evaporative cooling.

The first air conditioners and refrigerators employed toxic or flammable gases like ammonia, methyl chloride, and propane which could result in fatal accidents when they leaked. Thomas Midgley, Jr. created the first chlorofluorocarbon gas, Freon, in 1928.

Freon is a trademark name owned by DuPont for any Chlorofluorocarbon (CFC), Hydrogenated CFC (HCFC), or Hydrofluorocarbon (HFC) refrigerant, the name of each including a number indicating molecular composition (R-11, R-12, R-22, R-134A). The blend most used in direct-expansion home and building comfort cooling is an HCFC known as R-22. It is to be phased out for use in new equipment by 2010 and completely discontinued by 2020. R-12 was the most common blend used in automobiles in the US until 1994 when most changed to R-134A. R-11 and R-12 are no longer manufactured in the US for this type of application, the only source for air conditioning purchase being the cleaned and purified gas recovered from other air conditioner systems. Several non-ozone depleting refrigerants have been developed as alternatives, including R-410A, invented by Honeywell (formerly AlliedSignal) in Buffalo, and sold under the Genetron (R) AZ-20 name. It was first commercially used by Carrier under the brand name Puron.

Innovation in air conditioning technologies continues, with much recent emphasis placed on energy efficiency, and on improving indoor air quality. Reducing climate change impact is an important area of innovation, because in addition to greenhouse gas emissions associated with energy use, CFCs, HCFCs and HFCs are, themselves, potent greenhouse gases when leaked to the atmosphere. For example, R-22 (also known as HCFC-22) has a global warming potential about 1,800 times higher than CO2. As an alternative to conventional refrigerants, natural alternatives like CO2 (R-744) have been proposed.

Air Conditioning

Just about every modern car, truck or SUV sold these days can be had with air conditioning. It's so common that most people take it for granted. You press the button for air conditioning in your car and — presto! — cold air starts to flow out of the car's

vents. It's easy, it's simple, and it's a major convenience. Could you imagine driving to a job interview in Phoenix, Ariz., if your car didn't have air conditioning? By the time you

got to your interview, you'd be a sweaty, stinky mess.

Have you ever wondered how the air conditioning in your vehicle works? If you're like most people, you probably haven't. But we're here to educate you painlessly. Air

conditioning is the process by which air is cooled and dehumidified. The air conditioning in your car, your home and your office all work the same way. Even your refrigerator is,

in effect, an air conditioner. While there are many physical principles that relate to air conditioning, this article sticks to the basics. It explains the general concepts of

automotive air conditioning, the components used and what you need to know to keep your car's A/C system working properly.

Did you know that when you turn on the A/C in your car, you are burning extra gasoline to make yourself feel cooler? It's weird to think that by burning something you become

cooler, but it's true.

Do you remember anything from your high school physics class? Don't worry; very few of the writers here at Edmunds.com do, either. Basically, air conditioning systems operate on the principles of evaporation and condensation.

Here's a simple example of evaporation. Imagine that you're swimming around in your neighbor's backyard pool on a summer day. As soon as you get out, you start to feel cooler. Why? The water on your body starts to evaporate and turns into water vapor. And as it evaporates, it draws heat away from your body, and you get goose bumps. Brrr! Now let's say your neighbor hands you a big glass of ice-cold lemonade. You take a sip and set it down on a table. After a minute or two, you notice that water has collected on the outside of the glass. This is condensation. The air surrounding the glass becomes cooler when it encounters the cold glass, and the water vapor the air is carrying condenses into water.

Both of these examples occur at normal atmospheric pressure. But higher pressures can also change a vapor (or a gas) into a liquid. For example, if you look at a typical butane cigarette lighter, you can see liquid inside it. But as soon as you push down on the button, butane gas comes out. Why? The butane is under high pressure inside the cigarette lighter. This high pressure causes the butane to take liquid form. As soon as the butane is released and it encounters normal atmospheric pressure, it turns back into a gas.

OK, those are the basic ideas. But how do they apply to making your car's vents blow cool air? The principles of evaporation and condensation are utilized in your car's A/C system by a series of components that are connected by tubing and hoses. There are six basic components: the compressor, condenser, receiver-drier, thermostatic expansion valve, the evaporator and the life-blood of the A/C system, the refrigerant.

Refrigerant is a liquid capable of vaporizing at a low temperature. In the past, R-12 refrigerant was used in cars. But this chlorofluorocarbon (CFC) is harmful to the earth's ozone layer. Consequently, all vehicles built after 1996 use R-134A, a more environmentally friendly refrigerant.

Here's how an air conditioning system and its components work.

Step One: The compressor is the power unit of the A/C system. It is powered by a drive belt connected to the engine's crankshaft. When the A/C system is turned on, the compressor pumps out refrigerant vapor under high pressure and high heat to the condenser.

Step Two: The condenser is a device used to change the high-pressure refrigerant vapor to a liquid. It is mounted ahead of the engine's radiator, and it looks very similar to a radiator with its parallel tubing and tiny cooling fins. If you look through the grille of a car and see what you think is a radiator, it is most likely the condenser. As the car moves, air flowing through the condenser removes heat from the refrigerant, changing it to a liquid state.

Step Three: Refrigerant moves to the receiver-drier. This is the storage tank for the liquid refrigerant. It also removes moisture from the refrigerant. Moisture in the system can freeze and then act similarly to cholesterol in the human blood stream, causing blockage.

Step Four: As the compressor continues to pressurize the system, liquid refrigerant under high pressure is circulated from the receiver-drier to the thermostatic expansion valve. The valve removes pressure from the liquid refrigerant so that it can expand and become refrigerant vapor in the evaporator.

Step Five: The evaporator is very similar to the condenser. It consists of tubes and fins and is usually mounted inside the passenger compartment. As the cold low-pressure refrigerant is released into the evaporator, it vaporizes and absorbs heat from the air in the passenger compartment. As the heat is absorbed, cool air will be available for the occupants of the vehicle. A blower fan inside the passenger compartment helps to distribute the cooler air.

Step Six: The heat-laden, low-pressure refrigerant vapor is then drawn into the compressor to start another refrigeration cycle.

As you can see, the process is pretty simple. Just about every vehicle's A/C system works

this way, though certain vehicles might vary by the exact type of components they have.

The best thing about air conditioning is that all you have to do is press a button to make it work. Air conditioning systems are pretty reliable. On a modern and relatively new vehicle, it is rare to have problems. And if there are problems, they are pretty much one of two things: No cool air or insufficient cool air. If you own an older car and its A/C system doesn't seem to be working properly, here are some general troubleshooting tips:

No Cool Air

Loose or broken drive belt Inoperative compressor or slipping compressor clutch Defective expansion valve Clogged expansion valve, receiver-drier or liquid refrigerant line Blown fuse Leaking component: any of the parts listed above or one of the A/C lines, hoses

or seals

Insufficient Cool Air Low refrigerant charge Loose drive belt Slipping compressor clutch Clogged condenser Clogged evaporator Slow leak in system Partially clogged filter or expansion valve

Most A/C repairs are best left to a repair shop. Recharging the refrigerant, in particular, requires special equipment that most people don't own. There are a couple things you can do, however. First, make sure to have the system checked regularly according to your vehicle's owner's manual. Second, if you live in a place with a cold climate, it might not make much sense to run the A/C during the winter months, but many shop technicians recommend running your A/C system regularly, because it contains a light mineral oil in the refrigerant to keep the compressor properly lubricated. The general rule of thumb is 10 minutes per month. Some heating, ventilation and air conditioning systems also engage the A/C compressor for defrost mode (for example, most GM vehicles).

Refrigerants

"Freon" is a trade name for a family of haloalkane refrigerants manufactured by DuPont and other companies. These refrigerants were commonly used due to their superior stability and safety properties. However, it has been shown that these chlorine-bearing refrigerants reach the upper atmosphere when they escape. Once the refrigerant reaches the stratosphere, UV radiation from the Sun cleaves the chlorine-carbon bond, yielding a

chlorine radical. These chlorine atoms catalyze the breakdown of ozone into diatomic oxygen, depleting the ozone layer that shields the Earth's surface from strong UV radiation. Each chlorine radical remains active as a catalyst unless it binds with another chlorine radical, forming a stable molecule and breaking the chain reaction. The use of CFC as a refrigerant was once common, being used in the refigerants R-11 and R-12. In most countries the manufacture and use of CFCs has been banned or severely restricted due to concerns about ozone depletion. In light of these environmental concerns, beginning on November 14, 1994, the Environmental Protection Agency has restricted the sale, possession and use of refrigerant to only licensed technicians, per Rules 608 and 609 of the EPA rules and regulations; failure to comply may result in criminal and civil sanctions. Newer and more environmentally-safe refrigerants such as HCFCs (R-22, used in most homes today) and HFCs (R-134a, used in most cars) have replaced most CFC use. HCFCs in turn are being phased out under the Montreal Protocol and replaced by hydrofluorocarbons (HFCs) such as R-410A, which lack chlorine. Carbon dioxide (R-744) is being rapidly adopted as a refrigerant in Europe and Japan. R-744 is an effective refrigerant with a global warming potential of 1. It must use higher compression to produce an equivalent cooling effect.

Air conditioning applications

Air conditioning engineers broadly divide air conditioning applications into comfort and process.

Comfort applications aim to provide a building indoor environment that remains relatively constant in a range preferred by humans despite changes in external weather conditions or in internal heat loads.

Air conditioning makes deep plan buildings feasible, for otherwise they'd have to be built narrower or with light wells so that inner spaces receive sufficient outdoor air via natural ventilation. Air conditioning also allows buildings to be taller since wind speed increases significantly with altitude making natural ventilation impractical for very tall buildings.

An air conditioner.

Comfort applications for various building types are quite different and may be categorized as

Low-Rise Residential buildings, including single family houses, duplexes, and small apartment buildings

High-Rise Residential buildings, such as tall dormitories and apartment blocks Commercial buildings, which are built for commerce, including offices, malls,

shopping centers, restaurants, etc. Institutional buildings, which includes hospitals, governmental, academic, and so

on. Industrial spaces where thermal comfort of workers is desired.

In addition to buildings, air conditioning can be used for many types of transportation — motor-cars and other land vehicles, trains, ships, aircraft, and spacecraft.

Process applications aim to provide a suitable environment for a process being carried out, regardless of internal heat and humidity loads and external weather conditions. Although often in the comfort range, it is the needs of the process that determine conditions, not human preference. Process applications include these:

Hospital operating theatres, in which air is filtered to high levels to reduce infection risk and the humidity controlled to limit patient dehydration. Although temperatures are often in the comfort range, some specialist procedures such as open heart surgery require low temperatures (about 18 °C, 64 °F) and others such as neonatal relatively high temperatures (about 28 °C, 82 °F).

Cleanrooms for the production of integrated circuits, pharmaceuticals, and the like, in which very high levels of air cleanliness and control of temperature and humidity are required for the success of the process.

Facilities for breeding laboratory animals. Since many animals normally only reproduce in spring, holding them in rooms at which conditions mirror spring all year can cause them to reproduce year-round.

Aircraft air conditioning. Although nominally aimed at providing comfort for passengers and cooling of equipment, aircraft air conditioning presents a special challenge because of the changing density associated with changes in altitude, humidity and temperature of the outside air.

Data centers Textile factories Physical testing facilities Plants and farm growing areas Nuclear facilities Chemical and biological laboratories Mines Industrial environments Food cooking and processing areas

In both comfort and process applications, the objective may be to not only control temperature, but also humidity, air quality and air movement from space to space.

Humidity control

Air conditioning units outside a classroom building at the University of North Carolina in Chapel Hill, North Carolina

Refrigeration air conditioning equipment usually reduces the humidity of the air processed by the system. The relatively cold (below the dewpoint) evaporator coil condenses water vapor from the processed air, (much like an ice-cold drink will condense water on the outside of a glass), sending the water to a drain and removing water vapor from the cooled space and lowering the relative humidity. Since humans perspire to provide natural cooling by the evaporation of perspiration from the skin, drier air (up to a point) improves the comfort provided. The comfort air conditioner is designed to create a 40% to 60% relative humidity in the occupied space. In food retailing establishments, large open chiller cabinets act as highly effective air dehumidifying units.

A specific type of air conditioner that is used only for dehumidifying is called a dehumidifier. A dehumidifier is different from a regular air conditioner in that both the evaporator and condensor coils are placed in the same air path, and the entire unit is placed in the environment that is intended to be conditioned (in this case dehumidified), rather than requiring the condensor coil to be outdoors. Having the condensor coil in the same air path as the evaporator coil produces warm, dehumidified air. The evaporator

(cold) coil is placed first in the air path, dehumidifying the air exactly as a regular air conditioner does. The air next passes over the condensor coil re-warming the now dehumidified air. Note that the terms "condensor coil" and "evaporator coil" do not refer to the behavior of water in the air as it passes over each coil; instead they refer to the phases of the refrigeration cycle. Having the condensor coil in the main air path rather than in a separate, outdoor air path (as in a regular air conditioner) results in two consequences—the output air is warm rather than cold, and the unit is able to be placed anywhere in the environment to be conditioned, without a need to have the condensor outdoors.

Unlike a regular air conditioner, a dehumidifier will actually heat a room just as an electric heater that draws the same amount of power (watts) as the dehumidifier. A regular air conditioner transfers energy out of the room by means of the condensor coil, which is outside the room (outdoors). This is a thermodynamic system where the room serves as the system and energy is transferred out of the system. Conversely with a dehumidifier, no energy is transferred out of the thermodynamic system (room) because the air conditioning unit (dehumidifier) is entirely inside the room. Therefore all of the power consumed by the dehumidifier is energy that is input into the thermodynamic system (the room), and remains in the room (as heat). In addition, if the condensed water has been removed from the room, the amount of heat needed to boil that water has been added to the room. This is the inverse of adding water to the room with an evaporative cooler.

Dehumidifiers are commonly used in cold, damp climates to prevent mold growth indoors, especially in basements. They are also sometimes used in hot, humid climates

for comfort because they reduce the humidity which causes discomfort (just as a regular air conditioner, but without cooling the room).

The engineering of physical and thermodynamic properties of gas-vapor mixtures is named Psychrometrics

Health implications

A poorly maintained air-conditioning system can occasionally promote the growth and spread of microorganisms, such as Legionella pneumophila, the infectious agent responsible for Legionnaires' disease, or thermophilic actinomycetes, but as long as the air conditioner is kept clean these health hazards can be avoided. Conversely, air conditioning, including filtration, humidification, cooling, disinfection, etc., can be used to provide a clean, safe, hypoallergenic atmosphere in hospital operating rooms and other environments where an appropriate atmosphere is critical to patient safety and well-being. Air conditioning can have a positive effect on sufferers of allergies and asthma.

In serious heat waves, air conditioning can save the lives of the elderly. Some local authorities have even set up public cooling centers for people without home air conditioning.

Energy use

In a thermodynamically closed system, any energy input into the system that is being maintained at a set temperature (which is a standard mode of operation for modern air conditioners) requires that the energy removal rate from the air conditioner increases. This increase has the effect that for each unit of energy input into the system (say to power a light bulb in the closed system) this requires the air conditioner to remove that energy. In order to do that the air conditioner must increase its consumption by the inverse of its efficiency times the input of energy. As an example, presume that inside the closed system a 100 watt light bulb is activated, and the air conditioner has an efficiency of 200%. The air conditioner's energy consumption will increase by 50 W to compensate for this, thus making the 100 W light bulb use a total of 150 W of energy.

It is typical for air conditioners to operate at "efficiencies" of significantly greater than 100%..However it may be noted that the input (electrical) energy is of higher thermodynamic quality than the output which is basically thermal energy (heat dissipated), See Coefficient of performance.

Automobile air conditioners

Air conditioning systems are designed to allow the driver and or passengers to feel more comfortable during uncomfortably warm humid or hot trips in a vehicle. Cars in hot climates often are fitted with air conditioning. There has been much debate and discussion on what the usage of an air conditioner does to the fuel efficiency of a vehicle. Factors such as wind resistance, aerodynamics and engine power and weight have to be factored into finding the true variance between using the air conditioning system and not using it when figuring out difference in actual gas mileage. Other factors on the impact on the engine and an overall engine heat increase can have an impact on the cooling system of the vehicle.

1953 Chrysler Imperial with factory trunk mounted "Airtemp"

The Packard Motor Car Company was the first automobile manufacturer to build air conditioners into its cars, beginning in 1939. These air conditioners were originally optional, and could be installed for an extra $274 (about $4,050 in 2007 dollars). The system took up half of the entire trunk space, was not very efficient, and had no thermostat or independent shut-off mechanism. The option was discontinued after 1941.

In 1954, the Nash Ambassador was the first American automobile to boast front-end, fully-integrated heating, ventilating, and air-conditioning system. The Nash-Kelvinator Corporation used its experience in refrigeration to introduce the automobile industry's first compact and affordable, single-unit heating and air conditioning system optional for its 1954 Nash models. This was the first system for the mass market with controls on the dash and an electric clutch. Marketed under the name of "All-Weather Eye", the Nash system was "a good and remarkably inexpensive" system. Entirely incorporated within the engine bay, the combined heating and cooling system had cold air for passengers enter through dash-mounted vents. Nash's exclusive "remarkable advance" was not only the "sophisticated" unified system, but also its $345 price that beat all other systems.

Most competing systems used a separate heating system and an engine-mounted compressor, driven off of the crankshaft of the engine via a belt, with an evaporator in the car's trunk to deliver cold air through the rear parcel shelf and overhead vents. General Motors made a front mounted air conditioning system optional in 1954 on Pontiacs with a straight eight engine that added separate controls and air distribution. The alternative

layout pioneered by Nash "became established practice and continues to form the basis of the modern and more sophisticated automatic climate control systems.

The innovation was adopted quickly, and by 1960 about 20% of all cars in the U.S. had air-conditioning, with the percentage increasing to 80% in the warm areas of the Southwest. American Motors made air conditioning standard equipment on all AMC Ambassadors starting with the 1968 model year, a first in the mass market with a base price starting at $2,671. By 1969, 54% of the domestic automobiles were equipped with air conditioning, with the system needed not only for passenger comfort, but also to increase the car's resale value.

Portable air conditioners

A portable air conditioner is one on wheels that can be easily transported inside a home or office. They are currently available with capacities of about 6,000-60,000 BTU/h (1,800-18,000 W output) and with and without electric resistance heaters. Portable air conditioners are either evaporative or refrigerative.

Portable refrigerative air conditioners come in two forms, split and hose. These compressor-based refrigerant systems are air-cooled, meaning they use air to exchange heat, in the same way as a car or typical household air conditioner. Such a system dehumidifies the air as it cools it. It collects water condensed from the cooled air, and produces hot air which must be vented outside the cooled area; doing so transfers heat from the air in the cooled area to the outside air.

A portable split system has an indoor unit on wheels connected to an outdoor unit via flexible pipes, similar to a permanently fixed installed unit.

Hose systems, which can be air-to-air or monoblock, are vented to the outside via air ducts. The monoblock type collects the water in a bucket or tray and stops when full. The air-to-air type re-evaporates the water and discharges it through the ducted hose, and can run continuously.

A single-duct unit draws air out of the room to cool its condenser, and then vents it outside. This air is replaced by hot air from outside or other rooms, thus reducing efficiency. Modern units might have a COP (Coefficient Of Performance, sometimes called "efficiency") of approximately 3 i.e., 1 kW of electricity will produce 3 kW of cooling. A dual-duct unit draws air from outside to cool its condenser instead of from inside the room, and thus is more efficient than most single-duct units.

Evaporative air coolers, sometimes called "swamp air conditioners", do not have a compressor or condenser. Liquid water is evaporated on the cooling fins, releasing the vapour into the cooled area. Evaporating water absorbs a significant amount of heat, the latent heat of vaporisation, cooling the air — humans and other animals use the same mechanism to cool themselves by sweating. Disadvantages are that unless ambient humidity is low (as in a dry climate) cooling is limited and the cooled air is very humid and can feel clammy. They have the advantage of needing no hoses to vent heat outside the cooled area, making them truly portable; and they are very cheap to install and use less energy than refrigerative air conditioners.

Heat pumps

Heat pump is a term for a type of air conditioner in which the refrigeration cycle is able to be reversed, producing heat instead of cold in the indoor environment. They are also commonly referred to, and marketed as, a reverse cycle air conditioner. Using an air conditioner in this way to produce heat is significantly more efficient than electric resistance heating. Some home-owners elect to have a heat pump system installed, which is actually simply a central air conditioner with heat pump functionality (the refrigeration cycle is reversed in the winter). When the heat pump is enabled, the indoor evaporator coil switches roles and becomes the condenser coil, producing heat. The outdoor condensor unit also switches roles to serve as the evaporator, and produces cold air (colder than the ambient outdoor air).

Heat pumps are more popular in milder winter climates where the temperature is frequently in the range of 40-55°F (4-13°C), because heat pumps become inefficient in more extreme cold. This is due to the problem of the outdoor unit's coil forming ice, which blocks air flow over the coil. To compensate for this, the heat pump system must temporarily switch back into the regular air conditioning mode to switch the outdoor evaporator coil back to being the condenser coil so that it can heat up and de-ice. A heat pump system therefore will have a form of electric resistance heating in the indoor air path that is activated only in this mode in order to compensate for the temporary air conditioning, which would otherwise generate undesirable cold air in the winter. The icing problem becomes much more prevalent with lower outdoor temperatures, so heat pumps are commonly installed in tandem with a more conventional form of heating, such as a natural gas or oil furnace, which is used instead of the heat pump during harsher winter temperatures. In this case, the heat pump is used efficiently during the milder temperatures, and the system is switched to the conventional heat source when the outdoor temperature is lower.

Absorption heat pumps are actually a kind of air-source heat pumps, but they do not depend on electricity to power them. Instead, gas, solar power, or heated water is used as a main power source. Additionally, refrigerant isn’t used at all in the process. To extract heat, an absorption pump absorbs ammonia into water. Next, the water and ammonia mixture is pressurized to induce boiling, and the ammonia is boiled off.

Some more expensive window air conditioning units have the heat pump function. However, a window unit that has a "heat" selection is not necessarily a heat pump because some units use electric resistance heat when heating is desired. A unit that has true heat pump functionality will be indicated in its literature by the term "heat pump".

Working of an Air Conditioner

Air conditioners and refrigerators work the same way. Instead of cooling just the small, insulated space inside of a refrigerator, an air conditioner cools a room, a whole house, or an entire business.

Air conditioners use chemicals that easily convert from a gas to a liquid and back again. This chemical is used to transfer heat from the air inside of a home to the outside air.

The machine has three main parts. They are a compressor, a condenser and an evaporator. The compressor and condenser are usually located on the outside air portion of the air conditioner. The evaporator is located on the inside the house, sometimes as part of a furnace. That's the part that heats your house.

The working fluid arrives at the compressor as a cool, low-pressure gas. The compressor squeezes the fluid. This packs the molecule of the fluid closer together. The closer the molecules are together, the higher its energy and its temperature.

The working fluid leaves the compressor as a hot, high pressure gas and flows into the condenser. If you looked at the air conditioner part outside a house, look for the part that has metal fins all around. The fins act just like a radiator in a car and helps the heat go away, or dissipate, more quickly.

When the working fluid leaves the condenser, its temperature is much cooler and it has changed from a gas to a liquid under high pressure. The liquid goes into the evaporator through a very tiny, narrow hole. On the other side, the liquid's pressure drops. When it does it begins to evaporate into a gas.

As the liquid changes to gas and evaporates, it extracts heat from the air around it. The heat in the air is needed to separate the molecules of the fluid from a liquid to a gas.

The evaporator also has metal fins to help in exchange the thermal energy with the surrounding air.

By the time the working fluid leaves the evaporator, it is a cool, low pressure gas. It then returns to the compressor to begin its trip all over again.

Connected to the evaporator is a fan that circulates the air inside the house to blow across the evaporator fins. Hot air is lighter than cold air, so the hot air in the room rises to the top of a room.

There is a vent there where air is sucked into the air conditioner and goes down ducts. The hot air is used to cool the gas in the evaporator. As the heat is removed from the air, the air is cooled. It is then blown into the house through other ducts usually at the floor level.

This continues over and over and over until the room reaches the temperature you want the room cooled to. The thermostat senses that the temperature has reached the right setting and turns off the air conditioner. As the room warms up, the thermostat turns the air conditioner back on until the room reaches the temperature.

Heat Pump

Imagine that you took an air conditioner and flipped it around so that the hot coils were on the inside and the cold coils were on the outside. Then you would have a heater. It turns out that this heater works extremely well. Rather than burning a fuel, what it is doing is "moving heat."

A heat pump is an air conditioner that contains a valve that lets it switch between "air conditioner" and "heater." When the valve is switched one way, the heat pump acts like an air conditioner, and when it is switched the other way it reverses the flow of the liquid inside the heat pump and acts like a heater.

Heat pumps can be extremely efficient in their use of energy. But one problem with most heat pumps is that the coils in the outside air collect ice. The heat pump has to melt this ice periodically, so it switches itself back to air conditioner mode to heat up the coils. To avoid pumping cold air into the house in air conditioner mode, the heat pump also lights up burners or electric strip heaters to heat the cold air that the air conditioner is pumping out. Once the ice is melted, the heat pump switches back to heating mode and turns off the burners.

Heat pump Theory

Temperature & Heat

It is a common mistake to confuse temperature with heat even though they are two different things. Just because an object has a higher temperature doesn’t mean that it has a greater amount of heat than an object with a lower temperature.

Heat is the thermal energy that an object can contain. The heat must have a source. For example, the Sun emits radiant solar energy which will warm a rock or a swimming pool. Or the source can be fossil fuel which is burned to cook your steak on the gas grill. Heat can be measured in standard units- BTU. But in reality heat or energy is the force of life- we can’t create it from nothing nor can we destroy it.

Only for the sake of simplifying things and to understand the heat pump theory, I will give an example: (engineers and physicists will hate me)

Assume you have 1 gallon of water and it has 1,000 BTU in it (BTU is the amount of heat, and is the acronym for British thermal unit). Also, you have 2 gallons of water and

it has the same 1,000 BTU. Which water has higher temperature? You said the 1 gallon of water- yes, you are correct because the amount of heat is contained in a smaller object.

Another quick example: which has more heat your body, or the ocean? You said the ocean and you are correct. Even though it has a lower temperature than your body the ocean has more heat because the heat is contained in a very large object. But in your body the heat is contained in a relatively small object. Assume the ocean has millions of BTU but it has millions and millions of pounds of water so each 1 pound of water might have only 1 BTU. In your body you might have only 1,000 BTU but you are only 150 lb (my wife will love me if I am that skinny) so each pound of your body has 6.66 BTU- so your body has a higher temperature but less heat.

OK we’ve got the picture, let’s move on…

No… No… we don’t want anyone to hate us so we will give the scientific definition of Temperature.

“The average energy in each degree of freedom in the particles in a system”

The Laws of Thermodynamics

Thermo what? “Thermo dynamic” means in Greek the “movement of the heat”. and in order to understand the heat pump theory we have to understand those laws There are four laws that control that movement but we really need to know two.

The Zeroth Law of Thermodynamics

First- why do they call it Zeroth? Because it was understood fully only after the 1st law was invented- crazy right? Well it says,

“The heat moves from the Higher Temperature Object to the lower Temperature One”

Not from the higher heat to the lower heat but from the higher temperature to the lower temperature- remember the difference between heat and temperature. So when you jump into the ocean in January you will freeze your butt off, because all your body heat will move to the ocean and leave you in the cold even though the Ocean has more heat than you …..

The 1st Law of thermo Dynamic

This law says the “Heat can’t be created from nothing nor can it be destroyed. We can only transform it from one form to another”.

In layman’s terms you can’t have a fire without a fuel.

3rd and last principle (I promise)

The Temperature- Pressure Relationship

This one is easy- well kind of. If you pressurize a gas, you will increase its temperature. The reason is simply that you will decrease the volume, without adding or removing any heat. Remember the first example of the single gallon of water with 1,000 BTU and the 2 gallons of water, also with 1,000 BTU and how the single gallon had a higher temperature?

In this Example Container A contains a gas and the temperature of that gas is 80 F and the pressure is 10 PSI (pounds per square inch). Next we pressurize (compress) it as shown in Container B. The volume of the gas goes down. The pressure goes up (because we have increased it) and the temperature goes up because the heat has nowhere else to go. Heat is not added or removed- but since it is in a smaller volume of gas the temperature of that gas goes up.

And if you depressurize the container the gas will expand and you will drop its temperature.

A/C evaporator

Evaporator CoreThe a/c evaporator is like a small radiator but instead of containing hot antifreeze it contains cold Freon gas.  The cold Freon gas passes through the evaporator thus making the evaporator very cold.  The a/c blower fan is located behind the evaporator and blows air across it and that cold air travels through the dash duct work and out the vents inside the car.  Consider the evaporator like a block of ice in your hand and when you blow across it like the blower fan you get cold air.  The a/c water you see dripping from under the passenger side of the car is coming from condensation at the evaporator core.

Working of an air conditioning evaporator

Air conditioning evaporator works by absorb heat from the area (medium) that need to be cooled. It does that by maintaining the evaporator coil at low temperature and pressure than the surrounding air. Since, the AC evaporator coil contains refrigerant that absorbs heat from the surrounding air, the refrigerant temperature must be lower than the air.

The expansion device provides a pressure reduces between the high side and the low side of the system, the saturation temperature of the refrigerant entering the air conditioning evaporator is lower than the medium to be cooled.

One of the characteristic of a ac refrigerant is that as the pressure is reduced the boiling point is also reduced. Therefore, as the pressure is reduced through the expansion device so is the point at which it will boil and become a vapor.

As the warm air from the space passes over the evaporator coil, it gives up its heat to the lower temperature liquid/vapor mixture passing through the evaporator. As the liquid refrigerant absorbs this heat it boils changing from the liquid state to the vapor state.

For instance, if the air conditioning evaporator gives up 100 Btu’s of heat to the surrounding hot air, then the refrigerant within the air conditioning evaporator coil must gain 100 Btu’s of heat.

The amount of liquid entering the evaporator must be enough, so by the time it reaches the end of the evaporator. It will be completely boiled to the vapor state.

There must be enough air flows across the AC evaporator coil to provides heat to the refrigerant in the evaporator coil. This is just a safety way to ensure the air conditioner compressor doesn’t have the liquid refrigerant entering it.

Air conditioning evaporator picture above tells us what happen to the evaporator coil.

The air conditioning evaporator coil absorbs heat into the refrigerant from the warmer air passing over the surface of the evaporator coil. The heat absorbed causes the liquid refrigerant to boil, changing it from a liquid state to a vapor state.

Compressor

Working of an Air CompressorIn an air compressor, air is compressed by pulling in atmospheric air, reducing its volume and increasing its pressure. There are three major types of air compressor, namely, reciprocating, rotary and centrifugal compressor. Air compressor is a versatile device used for supplying the compressed air and/or power into a specific space. It is used for any purpose that requires air in the reduced volume or increased pressure. Air compressor is a vital mechanical device for the homeowners (refrigerators and air conditioners), jet engines, commercial businesses, refining industries, manufacturing industries and automotive industries. In fact, air compressor has been used in the industries for more than 100 years.

Types of air Compressor

Air compressors are available in various types, which are designed to meet different requirements. Each of the type of air compressor may differ in cooling method, compression stages, lubrication and power source. Following are the three major types of air compressors:

Reciprocating (Piston) Air CompressorReciprocating air compressor makes use of piston to compress air and store it in a storage tank. Based on the number of compression stages, reciprocating type can be a single-stage or double-stage compressor. In single-stage, only one piston is used to compress air, whereas in double-stage compressor, there are two pistons for air compression.

Rotary Air CompressorRotary air compressor is similar to the positive displacement configuration of a reciprocating compressor. In rotary type, two spinning helical mated screws are used rather than piston(s). As the screws spin towards each other, air is compressed and pushed inside a storage tank.

Centrifugal Air CompressorCentrifugal air compressor or dynamic compressor is applicable when the demand for compress air is high. In this air compressor, a high speed rotating impeller increases velocity of air, which is directed towards a diffuser that converts the velocity of air into pressure. Centrifugal air compressor requires more energy to operate than the other two air compressors.

Air Compressor: WorkingAir compressor consists of two major components - compressing mechanism and a power source. The compressing mechanism can be a piston, rotating impeller or vane, whereas the power is supplied by an electric motor or other energy sources. The compressing mechanism, as the name suggests, helps in compressing atmospheric air by using energy from the power source.

The basic working principle of an air compressor is to compress atmospheric air, which is then used as per requirements. In the process, atmospheric air is drawn in through an intake valve; more and more air is pulled inside a limited space mechanically by means of piston, impeller or vane. Since the amount of pulled atmospheric air is increased in the receiver or storage tank, pressure is raised automatically.

In simpler terms, free or atmospheric air is compressed after reducing its volume and at the same time, increasing its pressure. There is a pressure setting knob that can be manipulated as per the requirement of the operator. When the pressure increases to the maximum pressure setting in the receiver or tank, the pressure switch shuts off the intake of air in the compressor. When the compressed air is used, the pressure level falls. As the pressure drops to a low pressure setting, the pressure switch is turned on, thus allowing the intake of atmospheric air. Thus, the cycle continues in an air compressor.

Working of different compressors

Most cooling systems, from residential air conditioners to large commercial and industrial chillers, employ the refrigeration process known as the vapour compression cycle. At the heart of the vapour compression cycle is the mechanical compressor. A compressor has two main functions: 1) to pump refrigerant through the cooling system and 2) to compress gaseous refrigerant in the system so that it can be condensed to liquid and absorb heat from the air or water that is being cooled or chilled (See the "How it Works" section of the article "Gas Engine Chillers" for an explanation of the vapour compression cycle).

There are many ways to compress a gas. As such, many different types of compressors have been invented over the years. Each type utilizes a specific and sometimes downright ingenious method to pressurize refrigerant vapour. The five types of compressors used in vapour compression systems are Reciprocating, Rotary, Centrifugal, Screw and Scroll.

Reciprocating CompressorsA reciprocating compressor uses the reciprocating action of a piston inside a cylinder to compress refrigerant. As the piston moves downward, a vacuum is created inside the cylinder. Because the pressure above the intake valve is greater than the pressure below it, the intake valve is forced open and refrigerant is sucked into the cylinder. After the piston reaches its bottom position it begins to move upward. The intake valve closes, trapping the refrigerant inside the cylinder. As the piston continues to move upward it compresses the refrigerant, increasing its pressure. At a certain point the pressure exerted by the refrigerant forces the exhaust valve to open and the compressed refrigerant flows out of the cylinder. Once the piston reaches it top-most position, it starts moving downward again and the cycle is repeated.

Rotary Compressors

In a rotary compressor the refrigerant is compressed by the rotating action of a roller inside a cylinder. The roller rotates eccentrically (off-centre) around a shaft so that part of the roller is always in contact with the inside wall of the cylinder. A spring-mounted blade is always rubbing against the roller. The two points of contact create two sealed areas of continuously variable volume inside the cylinder. At a certain point in the rotation of the roller, the intake port is exposed and a quantity of refrigerant is sucked into the cylinder, filling one of the sealed areas. As the roller continues to rotate the volume of the area the refrigerant occupies is reduced and the refrigerant is compressed. When the exhaust valve is exposed, the high-pressure refrigerant forces the exhaust valve to open and the refrigerant is released. Rotary compressors are very efficient because the actions of taking in refrigerant and compressing refrigerant occur simultaneously.

Screw Compressors

Screw compressors use a pair of helical rotors As the rotors rotate they intermesh, alternately exposing and closing off interlobe spaces at the ends of the rotors. When an

interlobe space at the intake end opens up, refrigerant is sucked into it. As the rotors continue to rotate the refrigerant becomes trapped inside the interlobe space and is forced along the length of the rotors. The volume of the interlobe space decreases and the refrigerant is compressed. The compressed refrigerant exists when the interlobe space reaches the other end. . (Male and female) inside a sealed chamber.

Centrifugal Compressors

Centrifugal compressors use the rotating action of an impeller wheel to exert centrifugal force on refrigerant inside a round chamber (volute). Refrigerant is sucked into the impeller wheel through a large circular intake and flows between the impellers. The impellers force the refrigerant outward, exerting centrifugal force on the refrigerant. The refrigerant is pressurized as it is forced against the sides of the volute. Centrifugal compressors are well suited to compressing large volumes of refrigerant to relatively low pressures. The compressive force generated by an impeller wheel is small, so chillers that use centrifugal compressors usually employ more than one impeller wheel, arranged in series. Centrifugal compressors are desirable for their simple design and few moving parts.

Scroll Compressors

In a scroll compressor refrigerant is compressed by two offset spiral disks that are nested

together. The upper disk is stationary while the lower disk moves in orbital fashion. The orbiting action of the lower disk inside the stationary disk creates sealed spaces of varying volume. Refrigerant is sucked in through inlet ports at the perimeter of the scroll. A quantity of refrigerant becomes trapped in one of the sealed spaces. As the disk orbits the enclosed space containing the refrigerant is transferred toward the centre of the disk and its volume decreases. As the volume decreases, the refrigerant is compressed. The compressed refrigerant is discharged through a port at the centre of the upper disk. Scroll compressors are quiet, smooth-operating units with the highest efficiency ratio of all compressor types. They are commonly used in automobile air conditioning systems and commercial chillers. upper disk. Scroll compressors are quiet, smooth-operating units with the highest efficiency ratio of all compressor types. They are commonly used in automobile air conditioning systems and commercial chillers.

 

A compressor is commonly referred to as the heart of the system; the compressor is a belt

driven pump that is fastened to the engine. It is responsible for compressing and

transferring refrigerant gas.

The A/C system is split into two sides, a high pressure side and a low pressure side;

defined as discharge and suction. Since the compressor is basically a pump, it must have

an intake side and a discharge side. The intake, or suction side, draws in refrigerant gas

from the outlet of the evaporator. In some cases it does this via the accumulator.

Once the refrigerant is drawn into the suction side, it is compressed and sent to the

condenser, where it can then transfer the heat that is absorbed from the inside of the

vehicle.

Pressure Regulating Devices

Controlling the evaporator temperature can be accomplished by controlling refrigerant

pressure and flow into the evaporator. Many variations of pressure regulators have been

introduced since the 1940's. Listed below, are the most commonly found.

Orifice Tube

The orifice tube, probably the most commonly used, can be found in most GM and Ford

models. It is located in the inlet tube of the evaporator, or in the liquid line, somewhere

between the outlet of the condenser and the inlet of the evaporator. This point can be

found in a properly functioning system by locating the area between the outlet of the

condenser and the inlet of the evaporator that suddenly makes the change from hot to

cold.

You should then see small dimples placed in the line that keep the orifice tube from

moving. Most of the orifice tubes in use today measure approximately three inches in

length and consist of a small brass tube, surrounded by plastic, and covered with a filter

screen at each end. It is not uncommon for these tubes to become clogged with small

debris. While inexpensive, usually between three to five dollars, the labor to replace one

involves recovering the refrigerant, opening the system up, replacing the orifice tube,

evacuating and then recharging. With this in mind, it might make sense to install a larger

pre filter in front of the orifice tube to minimize the risk of of this problem reoccurring.

Some Ford models have a permanently affixed orifice tube in the liquid line. These can

be cut out and replaced with a combination filter/orifice assembly.

Thermal Expansion Valve

Another common refrigerant regulator is the thermal expansion valve, or TXV.

Commonly used on import and aftermarket systems. This type of valve can sense both

temperature and pressure, and is very efficient at regulating refrigerant flow to the

evaporator. Several variations of this valve are commonly found. Another example of a

thermal expansion valve is Chrysler's "H block" type. This type of valve is usually

located at the firewall, between the evaporator inlet and outlet tubes and the liquid and

suction lines.

These types of valves, although efficient, have some disadvantages over orifice tube

systems. Like orifice tubes these valves can become clogged with debris, but also have

small moving parts that may stick and malfunction due to corrosion.

Receiver-Drier

The receiver-drier is used on the high side of systems that use a thermal expansion valve.

This type of metering valve requires liquid refrigerant. To ensure that the valve gets

liquid refrigerant, a receiver is used. The primary function of the receiver-drier is to

separate gas and liquid. The secondary purpose is to remove moisture and filter out dirt.

The receiver-drier usually has a sight glass in the top. This sight glass is often used to

charge the system. Under normal operating conditions, vapor bubbles should not be

visible in the sight glass.

The use of the sight glass to charge the system is not recommended in R-134a systems as

cloudiness and oil that has separated from the refrigerant can be mistaken for bubbles.

This type of mistake can lead to a dangerous overcharged condition. There are variations

of receiver-driers and several different desiccant materials are in use. Some of the

moisture removing desiccants found within are not compatible with R-134a. The

desiccant type is usually identified on a sticker that is affixed to the receiver-drier. Newer

receiver-driers use desiccant type XH-7 and are compatible with both R-12 and R-134a

refrigerants.

Accumulator

Accumulators are used on systems that accommodate an orifice tube to meter refrigerants

into the evaporator. It is connected directly to the evaporator outlet and stores excess

liquid refrigerant. Introduction of liquid refrigerant into a compressor can do serious

damage. Compressors are designed to compress gas not liquid. The chief role of the

accumulator is to isolate the compressor from any damaging liquid refrigerant.

Accumulators, like receiver-driers, also remove debris and moisture from a system. It is a

good idea to replace the accumulator each time the system is opened up for major repair

and anytime moisture and/or debris is of concern. Moisture is enemy number one for

your A/C system. Moisture in a system mixes with refrigerant and forms a corrosive acid.

When in doubt, it may be to your advantage to change the Accumulator or receiver in

your system. While this may be a temporary discomfort for your wallet, it is of long term

benefit to your air conditioning system.

Conclusion

To have a comfortable journey in our automobile (car) the conditions needs to be favorable, one of the main aspect is the inside temperature of a car. In this project I have studied the air conditioning system of an automobile. The temperature inside the car should not be too hot or too cold, due to which the people inside it will feel unsecured or uncomfortable. Therefore there should be a perfect air conditioning system in the car for human comfort. In this project I have studied the working and mechanism of air conditioning system of an automobile. This helps in good and comfortable journey.