
Automotive air conditioning systems use
air conditioning
Air conditioning, often abbreviated as A/C (US) or air con (UK), is the process of removing heat from an enclosed space to achieve a more comfortable interior temperature, and in some cases, also controlling the humidity of internal air. Air c ...
to cool the
air
An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...
in a vehicle.
History
A company in
New York City
New York, often called New York City (NYC), is the most populous city in the United States, located at the southern tip of New York State on one of the world's largest natural harbors. The city comprises five boroughs, each coextensive w ...
in the United States first offered the installation of air conditioning for cars in 1933. Most of their customers operated
limousine
A limousine ( or ), or limo () for short, is a large, chauffeur-driven luxury vehicle with a partition between the driver compartment and the passenger compartment which can be operated mechanically by hand or by a button electronically. A luxu ...
s and
luxury cars
A luxury car is a passenger automobile providing superior comfort levels, features, and equipment. More expensive materials and surface finishes are used, and buyers expect a correspondingly high build quality.
The term is relative and unavo ...
.
On 7 October 1935,
Ralph Peo of
Houde Engineering,
Buffalo, New York
Buffalo is a Administrative divisions of New York (state), city in the U.S. state of New York (state), New York and county seat of Erie County, New York, Erie County. It lies in Western New York at the eastern end of Lake Erie, at the head of ...
, applied for a patent for an "Air Cooling Unit for Automobiles". , was granted on 16 November 1937.
In 1939,
Packard
Packard (formerly the Packard Motor Car Company) was an American luxury automobile company located in Detroit, Michigan. The first Packard automobiles were produced in 1899, and the last Packards were built in South Bend, Indiana, in 1958.
One ...
became the first automobile manufacturer to offer an optional air conditioning unit in its 1940 model year cars. These bulky units were manufactured by Bishop and Babcock (B&B), of
Cleveland
Cleveland is a city in the U.S. state of Ohio and the county seat of Cuyahoga County. Located along the southern shore of Lake Erie, it is situated across the Canada–U.S. maritime border and approximately west of the Ohio-Pennsylvania st ...
, Ohio and were ordered on approximately 2,000 cars.
The "Bishop and Babcock Weather Conditioner" also incorporated a heater. Cars ordered with this option were shipped from Packard's East Grand Boulevard facility to the B&B factory where the installation was performed. Once complete, the car was shipped to a local dealer for delivery to customers.
Packard warranted and supported this conversion. However, it was not commercially successful because:
*The main evaporator and blower system took up half of the trunk space (though this became less of a problem as trunks became larger in the post-war period).
*It was superseded by more efficient systems in the post-war years.
*It had no temperature thermostat or shut-off mechanism other than switching the blower off. (Cold air would still sometimes enter the car with any movement as the drive belt was continuously connected to the compressor—later systems would use electrically operated clutches to avoid this)
*The several feet of plumbing going back and forth between the engine compartment and trunk proved unreliable in service.
*The price, at $274 (US$ in dollars), was unaffordable to most people in depression/pre-war America.
The option was discontinued after 1941.
[
]
Chrysler Airtemp
The 1953 Chrysler Imperial
The Chrysler Imperial, introduced in 1926, was Chrysler (division), Chrysler's top-of-the-line vehicle for much of its history. Models were produced under the Chrysler name until 1954, after which Imperial became Imperial (automobile), a standal ...
was one of the first production cars in twelve years to offer modern automobile air conditioning as an option, following tentative experiments by Packard
Packard (formerly the Packard Motor Car Company) was an American luxury automobile company located in Detroit, Michigan. The first Packard automobiles were produced in 1899, and the last Packards were built in South Bend, Indiana, in 1958.
One ...
in 1940 and Cadillac
Cadillac Motor Car Division, or simply Cadillac (), is the luxury vehicle division (business), division of the American automobile manufacturer General Motors (GM). Its major markets are the United States, Canada and China; Cadillac models are ...
in 1941. Walter Chrysler
Walter Percy Chrysler (April 2, 1875 – August 18, 1940) was an American industrial pioneer in the automotive industry, automotive industry executive, and the founder and namesake of American Chrysler, Chrysler Corporation.
Childhood
Chrysler ...
had seen to the invention of Airtemp air conditioning in the 1930s for the Chrysler Building
The Chrysler Building is a , Art Deco skyscraper in the East Midtown neighborhood of Manhattan, New York City, United States. Located at the intersection of 42nd Street and Lexington Avenue, it is the tallest brick building in the world wit ...
, and had offered it on cars in 1941-42, and again in 1951-52.
The Airtemp was more advanced than rival automobile air conditioners by 1953. It was operated by a single switch on the dashboard marked with low, medium, and high positions. As the highest capacity unit available at that time, the system was capable of quickly cooling the passenger compartment and also reducing humidity, dust, pollen, and tobacco smoke. The system drew in more outside air than contemporary systems; thus, reducing the staleness associated with automotive air conditioning at the time. Instead of plastic tubes mounted on the rear window package shelf as on GM cars, small ducts directed cool air toward the ceiling of the car where it filtered down around the passengers instead of blowing directly on them, a feature that modern cars have lost.[
Cadillac, ]Buick
Buick () is a division (business), division of the Automotive industry in the United States, American automobile manufacturer General Motors (GM). Started by automotive pioneer David Dunbar Buick in 1899, it was among the first American automobil ...
, and Oldsmobile
Oldsmobile (formally the Oldsmobile Division of General Motors) was a brand of American automobiles, produced for most of its existence by General Motors. Originally established as "Olds Motor Vehicle Company" by Ransom E. Olds in 1897, it produc ...
added air conditioning as an option on some of their models for the 1953 model year. All of these Frigidaire
Frigidaire Appliance Company is the American consumer and Commercial area, commercial home appliances brand subsidiary of multinational company Electrolux, a Swedish multinational home appliance manufacturer, headquartered in Stockholm.
History ...
systems used separate engine and trunk mounted components.
Nash integrated system
In 1954, the Nash Ambassador
The Nash Ambassador is a luxury automobile produced by Nash Motors from 1927 until 1957. It was a top trim level for the first five years, then from 1932 on a standalone model. Ambassadors were lavishly equipped and beautifully constructed, ear ...
was the first American automobile to have a front-end, fully integrated heating, ventilating, and air-conditioning system. The Nash-Kelvinator
Nash-Kelvinator Corporation was the result of a merger in 1937 between Nash Motors and Kelvinator Appliance Company. The union of these two companies was brought about as a result of a condition made by George W. Mason prior to his appointment a ...
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 Nash models. This was the first mass market system with controls on the dash and an electric clutch. This system was also compact and serviceable with all of its components installed under the hood or in the cowl area.
Combining heating, cooling, and ventilating, the new air conditioning system for the Nash cars was called the "All-Weather Eye". This followed the marketing name of "Weather Eye
The Weather Eye was a trade name for a Nash Motors-designed fresh-air system for automobile passenger compartment heating, cooling, and ventilating. The Nash "All-Weather Eye" was the first automobile air conditioning system for the mass marke ...
" for Nash's fresh-air automotive heating and ventilating system that was first used in 1938.[ With a single thermostatic control, the Nash passenger compartment air cooling option was "a good and remarkably inexpensive" system. The 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 by the engine crankshaft 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 offered a front-mounted air conditioning system made by its Harrison Division on 1954 Pontiacs with a straight-eight engine
The straight-eight engine or inline-eight engine (often abbreviated as I8) is an eight-cylinder internal combustion engine with all eight cylinders mounted in a straight line along the crankcase. The type has been produced in side-valve, IO ...
. It was very expensive and not a fully integrated system with separate controls and ducts for air distribution. The heater core
A heater core is a radiator (engine cooling), radiator-like device used in heating the cabin of a vehicle. Hot coolant from the vehicle's engine is passed through a winding tube of the core, a heat exchanger between coolant and cabin air. Fins att ...
continued to be a separate "Venti-Seat" or under the front seat system with its own controls. The unified alternative layout pioneered by Nash "became established practice and continues to form the basis of the modern and more sophisticated automatic climate control systems."
Growth in application
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.
Cadillac introduced the industry's first Comfort Control which was a completely automatic heating and cooling system set by dial thermostat for the 1964 model year.
American Motors Corporation
American Motors Corporation (AMC; commonly referred to as American Motors) was an American automobile manufacturing company formed by the mergers and acquisitions, merger of Nash-Kelvinator Corporation and Hudson Motor Car Company on May 1, 19 ...
(AMC) made air conditioning standard equipment on all AMC Ambassador
The Ambassador is an automobile manufactured and marketed by American Motors Corporation (AMC) from 1957 through 1974 over eight generations, available in two- and four-door sedan, two-door hardtop, four-door station wagon as well as two-door c ...
s starting with the 1968 model year, an innovation in the mass market with the base prices of the cars starting at $2,671. At the time, air conditioning was standard only on Cadillac limousines and Rolls-Royce
Rolls-Royce (always hyphenated) may refer to:
* Rolls-Royce Limited, a British manufacturer of cars and later aero engines, founded in 1906, now defunct
Automobiles
* Rolls-Royce Motor Cars, the current car manufacturing company incorporated in ...
s.
By 1969, 54% of domestic automobiles were equipped with air conditioning, a feature needed not only for passenger comfort, but also to increase the car's resale value.
Air-conditioning for automobiles came into widespread use in the United States starting from the 1980s. Adoption was slower elsewhere; in 1990 less than eight percent of cars sold in Europe were thus equipped.
Evaporative cooling
A car cooler is an automobile evaporative cooler
An evaporative cooler (also known as evaporative air conditioner, swamp cooler, swamp box, desert cooler and wet air cooler) is a device that cools air through the evaporation of water. Evaporative cooling differs from other air conditioning sy ...
, sometimes referred to as a swamp cooler. Most are aftermarket relatively inexpensive accessories consisting of an external window-mounted metal cylinder without moving parts, but internal under the dashboard or center floor units with an electric fan are available. It was an early type of automobile air conditioner[Hinckley, p. 54] and is not used in modern cars relying on refrigerative systems to cool the interior.
To cool the air it used latent heat
Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process—usually a first-order phase transition, like melting or condensation. ...
(in other words, cooling by water evaporation).[Sibley, p. 221] Water inside the device evaporates and in the process transfers heat from the surrounding air. The cool moisture-laden air is then directed to the inside of the car.[ The evaporate "cooling" effect decreases with ]humidity
Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog t ...
because the air is already saturated with water. Therefore, the lower the humidity
Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation (meteorology), precipitation, dew, or fog t ...
, such as in dry desert regions, the better the system works. Car coolers were popular, especially among summer tourists visiting or crossing the southwestern United States states of California, Arizona, Texas, New Mexico, and Nevada.[
]
Types of automotive air conditioning refrigerants
R-12
R-12, the first automotive air conditioning refrigerant, was invented in 1928 by a team of scientists put together by Thomas Midgley, Jr. The team of scientists set out to create refrigerants which led to the invention of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). From these two inventions, two refrigerants were created, R-12 and R-22. For many decades, both of these refrigerants could commonly be found in households and businesses. R-12 was also used in automotive air conditioning systems because it was the first safe non-flammable refrigerant. This refrigerant was the industry standard until the 1970s when scientists discovered that R-12 contained chlorine which depleted the ozone layer in the earth’s atmosphere. When R-12 was released from either a leak in systems or improperly disposing of contaminated freon, the gaseous freon would go up into the atmosphere. Chlorine molecules from the refrigerant would break up ozone molecules in the atmosphere, which produced holes in the ozone, that in turn contributed to the destruction of the ozone layer. R-12 continued to be used until a new refrigerant could be invented that had fewer negative effects. R-12 was used in automotive air conditioning systems until the mid-90s when production was banned by the government and replaced with a new refrigerant, R-134a. R-12 can still be bought and sold but is no longer produced. This makes R-12 very expensive and hard to find. R-12’s global warming potential number is very large at about 11,000.
R-134a
The second automotive air conditioning refrigerant invented was R-134a. R-134a is a hydrofluorocarbon
Hydrofluorocarbons (HFCs) are synthetic organic compounds that contain fluorine and hydrogen atoms, and are the most common type of organofluorine compounds. Most are gases at room temperature and pressure. They are frequently used in air condit ...
refrigerant that contains fluorine and hydrogen. The successor to R-12, R-134a was a new refrigerant that no longer contained chlorine that could deplete the ozone layer. R-134a is a greenhouse gas, it has a lower global warming potential than R-12. New cars produced in the early 1990s contained the new refrigerant in their air conditioning systems. Owners of older cars with R-12 systems would either have to invest in an R-12 to R-134a conversion system, buy a new car, or find a qualified technician to recharge their older R-12 system. R-134a has been used in cars for almost 30 years. R-134a’s global warming potential number is about 1,430.[
]
R-1234yf
The third and newest automotive air conditioning refrigerant is R-1234yf. R-1234yf is a hydrofluoroolefin
Hydrofluoroolefins (HFOs) are Saturated and unsaturated compounds, unsaturated organic compounds composed of hydrogen, fluorine and carbon. These organofluorine compounds are of interest as refrigerants. Unlike traditional hydrofluorocarbons (HFCs ...
refrigerant that contains hydrogen, fluorine, and also carbon elements. The refrigerant was developed by the DuPont/Honeywell company and is more expensive per pound than R-134a. R-1234yf can be found in late-model cars and is not cross-compatible with older R-134a or R-12 systems. Of the three refrigerants, R-1234yf is the best for the environment with the lowest global warming potential number which is about a three.[
]
Operating principles
In the refrigeration cycle, heat is transported from the passenger compartment to the environment. A refrigerator
A refrigerator, commonly shortened to fridge, is a commercial and home appliance consisting of a thermal insulation, thermally insulated compartment and a heat pump (mechanical, electronic or chemical) that transfers heat from its inside to ...
is an example of such a system, as it transports the heat out of the interior and into the ambient environment.
Circulating refrigerant gas vapor (which also carries the compressor lubricant oil across the system along with it) from the evaporator enters the gas compressor
A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor.
Many compressors can be staged, that is, the gas is compressed several times in steps or ...
in the engine bay, usually an axial piston pump
An axial piston pump is a positive displacement pump that has a number of pistons in a circular array within a ''cylinder block''.
It can be used as a stand-alone pump, a hydraulic motor or an automotive air conditioning compressor.
Description
...
compressor, and is compressed to a higher pressure, resulting in a higher temperature as well. The hot, compressed refrigerant vapor is now at a temperature and pressure at which it can be condensed and is routed through a condenser, usually in front of the car's radiator. Here the refrigerant is cooled by air flowing across the condenser coils (originating from the vehicle's movement or from a fan, often the same fan of the cooling radiator if the condenser is mounted on it, automatically turned on when the vehicle is stationary or moving at low speeds) and condensed into a liquid. Thus, the circulating refrigerant ejects heat from the system and the heat is carried away by the air.
In a thermal expansion valve
A thermal expansion valve or thermostatic expansion valve (often abbreviated as TEV, TXV, or TX valve) is a component in vapor-compression refrigeration and air conditioning systems that controls the amount of refrigerant released into the evapor ...
air conditioning system, the condensed and pressurized liquid refrigerant is next routed through the receiver-drier, that is, a one-way desiccant and filter cartridge that both dehydrates the refrigerant and compressor lubricant oil mixture to remove any residual water content (which would become ice inside the expansion valve and therefore clog it) that the vacuum done before the charging process did not manage to remove from the system, and filters it to remove any solid particles carried by the mixture, in addition to acting as a storage vessel for any excess liquid refrigerant during low cooling demand periods, and then through the thermal expansion valve where it undergoes an abrupt reduction in pressure. That pressure reduction results in flash evaporation
Flash evaporation (or partial evaporation) is the partial vapor that occurs when a saturated liquid stream undergoes a reduction in pressure by passing through a throttling valve or other throttling device. This process is one of the simplest u ...
of a part of the liquid refrigerant, lowering its temperature. The cold refrigerant is then routed through the evaporator coil in the passenger compartment.
When the expansion device is a simple fixed metering orifice, known as an orifice tube, the receiver-drier is instead located between the evaporator outlet and the compressor, and in this case, it is known as an accumulator. In such an air conditioning system, the accumulator also prevents the liquid refrigerant from reaching the compressor during low cooling demand periods.
The air, often after being filtered by a cabin air filter
A particulate air filter is a device composed of fibrous, or porous materials which removes particulates such as smoke, dust, pollen, mold, viruses and bacteria from the air. Filters containing an adsorbent or catalyst such as charcoal (carbon) ...
, is blown by an adjustable speed electric powered centrifugal fan
A centrifugal fan is a mechanical device for moving air or other gases in a direction perpendicular to the axis of rotation of the fan. Centrifugal fans often contain a ducted fan, ducted housing to direct outgoing air in a specific direction or ...
across the evaporator, causing the liquid part of the cold refrigerant mixture to evaporate as well, further lowering the temperature. The warm air is therefore cooled, and also deprived of any humidity (which condenses on the evaporator coils and is drained outside of the vehicle) in the process. It is then passed through a heater matrix, inside of which the engine's coolant circulates, where it can be reheated to a certain degree or even a certain temperature selected by the user and then delivered inside the vehicle's cabin through a set of adjustable vents. Another way of adjusting the desired air temperature, this time by working on the system's cooling capacity
Cooling capacity is the measure of a cooling system's ability to remove heat. It is equivalent to the heat supplied to the evaporator/boiler part of the refrigeration cycle and may be called the "rate of refrigeration" or "refrigeration capacity". ...
, is precisely regulating the centrifugal fan speed so that only the strictly required volumetric flow rate
In physics and engineering, in particular fluid dynamics, the volumetric flow rate (also known as volume flow rate, or volume velocity) is the volume of fluid which passes per unit time; usually it is represented by the symbol (sometimes \do ...
of air is cooled by the evaporator. The user is also given the option to close the vehicle's external air flaps, to achieve even faster and stronger cooling by recirculating the already-cooled air inside the cabin to the evaporator. Finally, whenever the compressor can be commanded to operate in a reduced displacement, the vent temperature can also be controlled by acting upon the compressor's displacement.
Evaporator freeze over, which stops air from flowing through the evaporator fins, can be prevented in different ways. A temperature switch or a thermistor
A thermistor is a semiconductor type of resistor in which the resistance is strongly dependent on temperature. The word ''thermistor'' is a portmanteau of ''thermal'' and ''resistor''. The varying resistance with temperature allows these devices ...
can control the evaporator coil surface temperature, and a pressure switch or sensing element can monitor the suction pressure (which is in relationship with the refrigerant's evaporating temperature). Both control means can act (either directly or by means of a control unit fed by their data) upon the compressor's clutch engagement status or, in the case of a variable displacement compressor, its displacement; additionally, a secondary valve located on the suction side can throttle the refrigerant flow so that the evaporator's outlet pressure doesn't fall below a precise value during system operation.
To complete the refrigeration cycle
Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pump, air conditioning and refrigeration systems. A heat pump is a mechanical system that transmits heat from one location (the "source") a ...
, the refrigerant vapor is routed back into the compressor.
The warmer the air that reaches the evaporator, the higher the pressure of the vapor mixture discharged from it and therefore the higher the load placed on the compressor and therefore on the engine to keep the refrigerant flowing through the system. Compressor load is also proportional to the condensing temperature.
The compressor can be driven by the car's engine (e.g. via a belt, often the serpentine belt
A serpentine belt (or drive belt) is a single, continuous belt used to drive multiple peripheral devices in an automotive engine, such as an alternator, power steering pump, water pump, air conditioning compressor, air pump, etc. The belt may a ...
, and an electromagnetically actuated clutch; an electronically actuated variable displacement compressor can also be always directly driven by a belt without the need of any clutch and magnet at all) or by an electric motor.
There are different methods for the repair and maintenance of the tube connections ensuring the refrigeration cycle. Conventional methods like soldering
Soldering (; ) is a process of joining two metal surfaces together using a filler metal called solder. The soldering process involves heating the surfaces to be joined and melting the solder, which is then allowed to cool and solidify, creatin ...
or welding
Welding is a fabrication (metal), fabrication process that joins materials, usually metals or thermoplastics, primarily by using high temperature to melting, melt the parts together and allow them to cool, causing Fusion welding, fusion. Co ...
lead to time and damaging soiling issues. The Lokring connection which is based on compressed fittings is easy to use and thus more time-efficient.
Maintenance, hygiene & cleaning
Refrigerant Maintenance
Air conditioning
Air conditioning, often abbreviated as A/C (US) or air con (UK), is the process of removing heat from an enclosed space to achieve a more comfortable interior temperature, and in some cases, also controlling the humidity of internal air. Air c ...
systems in cars require special maintenance
The technical meaning of maintenance involves functional checks, servicing, repairing or replacing of necessary devices, equipment, machinery, building infrastructure and supporting utilities in industrial, business, and residential installa ...
. Normally the lifetime losses of refrigerant
A refrigerant is a working fluid used in the cooling, heating, or reverse cooling/heating cycles of air conditioning systems and heat pumps, where they undergo a repeated phase transition from a liquid to a gas and back again. Refrigerants are ...
are small and have no effect. But the system should be checked for any loss in a two to four year circle; at least, when the cooling capacity decreases.
Hygiene control
Biogrowth in air conditioning systems can be reduced for a limited time only. Hygiene
Hygiene is a set of practices performed to preserve health.
According to the World Health Organization (WHO), "Hygiene refers to conditions and practices that help to maintain health and prevent the spread of diseases." Personal hygiene refer ...
measures should be applied regularly. The Standard 6032 of the Association of German Engineers (VDI) provides an overview of the hygienic maintenance of vehicle air conditioning systems according to the state of the art. A regular, professional hygiene check of a vehicle's air conditioning system includes checking the drain lines for the condensation water, annual cleaning of the air conditioning system evaporator
An evaporator is a type of heat exchanger device that facilitates evaporation by utilizing conductive and convective heat transfer, which provides the necessary thermal energy for phase transition from liquid to vapour. Within evaporators, a ci ...
and changing the interior air filter (pollen filter). In particular, the unhindered drainage of the condensation water from the air conditioning system evaporator must be ensured, otherwise the moisture will remain within the system and uncontrolled nests for biological colonization will arise.
Due to the physical framework conditions, the forced separation of condensed water, air conditioning evaporators in motor vehicles have a very important health and hygiene function. Regular cleaning of the air conditioning evaporator must therefore ensure that the biological colonization of the surface is interrupted and that the sometimes toxic decay products of bacteria (endotoxins) or metabolites of mold (mycotoxins) are safely removed from the lamella system.
Hygienic air conditioning cleaning
The necessity of hygienic cleaning of ventilation systems in vehicles at regular intervals is not only logically understandable, but is also described by the technical guideline and standard VDI 6032 Standard may refer to:
Symbols
* Colours, standards and guidons, kinds of military signs
* Standard (emblem), a type of a large symbol or emblem used for identification
Norms, conventions or requirements
* Standard (metrology), an object th ...
of the Association of German Engineers
Verein Deutscher Ingenieure (VDI) (English: Association of German Engineers) is an organization of about 135,000 engineers and natural scientists. More than 12,000 honorary experts process the latest technical findings each year to promote the tec ...
. Particles such as Dust, (animal) hair and/or fungal growth, dander, etc. and remain on the pollen filter shaft and the surrounding walls. The air conditioner quickly becomes a dirt and germ spinner. Merely replacing the air filter of an HVAC system as part of the inspection is not enough. The pollen filter box must be cleaned professionally and the air conditioning system evaporator must be flushed hygienically and effectively with cleaners without fragrances (allergy triggers) every 24 months at the latest. With a professional air conditioning system cleaning according to the current state of the art, mould, germs, bacteria and other odor-forming substances or deposits are literally washed away at the point of origin. This is the only way to ensure the required indoor air hygiene in the vehicle. The choice of approved cleaning agents and methods is also crucial here. These were also clearly described by the VDI in the 6032 standard for cleaning air conditioning systems. With this method, the air conditioning evaporator is completely flushed with a cleaning liquid introduced through a probe. The evaporator is then as clean as a new component and completely free of deposits or substances that form a culture medium. Only the combination of mechanical cleaning and a cleaning agent ensures working results. Meanwhile, both the driver and all passengers are exposed to an invisible health risk. "In order to achieve a supply air quality that is conducive to health, the AC system must be .. professionally .. cleaned at regular intervals.“
Challenges for air filters
Air filters that are not replaced regularly (once or twice a year) often look as shown and are a source of germs, especially for mould. Pollen
Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...
decompose in the filter within 12 weeks. This decomposition process releases its actual allergen. These have a particle size that cannot be retained by the pollen filter. The air flow
Airflow, or air flow, is the movement of air. Air behaves in a fluid manner, meaning particles naturally flow from areas of higher pressure to those where the pressure is lower. Atmospheric air pressure is directly related to altitude, temperatu ...
through the pollen filter leads to an increasingly poor air quality inside the vehicle. Especially in overloaded filters that have been used for a long time, particle sizes develop that are below the filter performance. The particles of microorganisms, pollen, germs and bacteria are released directly to the moist surface environment of the air conditioning system evaporator via the clean air side of the filter. Therefore, the air conditioning evaporator should also be professionally cleaned once a year.
Challenges for air conditioning evaporators
The same applies to an air conditioning evaporator that is not professionally cleaned regularly. Bacteria also settle on its surface and lead to an ever increasing biogrowth due to the continuous moisture of the component. Hygienic problems also arise if the evaporator is cleaned incorrectly or treated with unsuitable cleaning agents. Cleaning agent
Cleaning agents or hard-surface cleaners are substances (usually liquids, powders, sprays, or granules) used to remove dirt, including dust, stains, foul odors, and clutter on surfaces. Purposes of cleaning agents include health, beauty, removing ...
s that are too harsh destroy or damage the protective coating of the fin evaporator structure. This can change the drip angle of the condensate and increases the discharge volume on the evaporator. The result is misdirected, bacterially contaminated condensate that accumulates in unexpected places within the air conditioning system.
The vehicle owner must personally ensure that the workshop carries out a hygienic cleaning of the air conditioning system using a chemical-mechanical process recommended by the VDI as part of the inspection or an upcoming air filter change. Since the method described has not yet become established in everyday workshop practice, the use of so-called "one click cans" is currently enjoying great popularity. Not only because they are printed with the addition "air conditioning cleaner". Most of the contents of these cans are randomly distributed in the vehicle and settle there. The part that could actually be sucked in by the ventilation system via the circulating air ends up on the cabin air filter. Nothing gets on the vaporizer with this method. Only scents and aromas are distributed in the vehicle with the click cans. Only the combination of mechanical pressure flushing and a suitable cleaning agent directly on the evaporator leads to the desired result.
Power consumption
Although air conditioners use significant power, the drag of a car with closed windows is less than if the windows are open to cool the occupants. There has been much debate on the effect of air conditioning on the fuel efficiency
Fuel efficiency (or fuel economy) is a form of thermal efficiency, meaning the ratio of effort to result of a process that converts chemical energy, chemical potential energy contained in a carrier (fuel) into kinetic energy or Mechanical work, w ...
of a vehicle. Factors such as wind resistance
In fluid dynamics, drag, sometimes referred to as fluid resistance, is a force acting opposite to the direction of motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers, two solid surfaces, or b ...
, aerodynamics, engine power, and weight
In science and engineering, the weight of an object is a quantity associated with the gravitational force exerted on the object by other objects in its environment, although there is some variation and debate as to the exact definition.
Some sta ...
must be considered, to find the true difference between using the air conditioning system and not using it, when estimating the actual fuel mileage. Other factors can affect the engine, and an overall engine heat increase can affect the cooling system of the vehicle.
In a modern automobile, the A/C system will use around of the engine's power
Power may refer to:
Common meanings
* Power (physics), meaning "rate of doing work"
** Engine power, the power put out by an engine
** Electric power, a type of energy
* Power (social and political), the ability to influence people or events
Math ...
, thus increasing fuel consumption
A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work. The concept was originally applied solely to those materials capable of releasing chemical energy but ...
of the vehicle.
Sustainable automotive air conditioning
Sustainable automotive air conditioning is the subject of a debate – also known as the ''Cool War'' – about the next-generation refrigerant
A refrigerant is a working fluid used in the cooling, heating, or reverse cooling/heating cycles of air conditioning systems and heat pumps, where they undergo a repeated phase transition from a liquid to a gas and back again. Refrigerants are ...
in car air conditioning
Air conditioning, often abbreviated as A/C (US) or air con (UK), is the process of removing heat from an enclosed space to achieve a more comfortable interior temperature, and in some cases, also controlling the humidity of internal air. Air c ...
. An advocacy group, ''The Alliance for CO2 Solutions'', supports the uptake of carbon dioxide (CO2) as a refrigerant in passenger cars, and the chemical industry
The chemical industry comprises the companies and other organizations that develop and produce industrial, specialty and other chemicals. Central to the modern world economy, the chemical industry converts raw materials ( oil, natural gas, air, ...
is developing new chemical blends.
The Alliance for CO2 Solutions propositions the car industry to replace more unsustainable
Sustainability is a social goal for people to co-exist on Earth over a long period of time. Definitions of this term are disputed and have varied with literature, context, and time. Sustainability usually has three dimensions (or pillars): env ...
chemical substances with the natural refrigerant
Natural refrigerants are considered substances that serve as refrigerants in refrigeration systems (including refrigerators, HVAC, and air conditioning). They are alternatives to synthetic refrigerants such as chlorofluorocarbon (CFC), hydrochloro ...
like carbon dioxide (CO2, R744/ R-744) in car cooling and heating. They claim that this would lead to 10% fewer emissions from new cars, potentially reducing global greenhouse gas emissions
Greenhouse gas (GHG) emissions from human activities intensify the greenhouse effect. This contributes to climate change. Carbon dioxide (), from burning fossil fuels such as coal, petroleum, oil, and natural gas, is the main cause of climate chan ...
by 1%.
Opponents of the advocacy group claim that CO2 refrigeration technology is not cost-efficient nor safe, and support the development of new chemical refrigerant blends instead.
Background
A debate had emanated from the decision of the European Union
The European Union (EU) is a supranational union, supranational political union, political and economic union of Member state of the European Union, member states that are Geography of the European Union, located primarily in Europe. The u ...
to phase out the current high global warming refrigerant HFC-134a
1,1,1,2-Tetrafluoroethane (also known as norflurane (INN), R-134a, Klea 134a, Freon 134a, Forane 134a, Genetron 134a, Green Gas, Florasol 134a, Suva 134a, HFA-134a, or HFC-134a) is a hydrofluorocarbon (HFC) and haloalkane refrigerant with thermo ...
in car air conditioning from January 2011 onwards. To comply with the legislation carmakers have to decide on new refrigerants, as they typically need 3 to 4 years to develop and introduce a new car platform including the new air conditioning system.
Arguments
Arguments for CO2
The Alliance for CO2 Solutions and its supporters agree that the refrigerant CO2 is:
*More environmentally friendly with the lowest global warming potential
Global warming potential (GWP) is a measure of how much heat a greenhouse gas traps in the atmosphere over a specific time period, relative to carbon dioxide (). It is expressed as a multiple of warming caused by the same mass of carbon dioxide ( ...
(GWP) of all currently used and proposed refrigerants. CO2 does not deplete the ozone layer
The ozone layer or ozone shield is a region of Earth's stratosphere that absorption (electromagnetic radiation), absorbs most of the Sun's ultraviolet radiation. It contains a high concentration of ozone (O3) in relation to other parts of the a ...
. Because the carbon dioxide used in car air conditioning is a recycled
Recycling is the process of converting waste materials into new materials and objects. This concept often includes the recovery of energy from waste materials. The recyclability of a material depends on its ability to reacquire the propert ...
industrial waste product, it is an environmentally neutral solution. The Alliance claims that using a CO2-based air conditioning system will reduce total car emissions by 10%, thereby sparing the planet 1% of total greenhouse gases.
*More technically ready because CO2 models have been developed and tested in all climates, being now ready for mass production. They are faster to heat and cool a car, and show superior performance in over 90% of all driving conditions.
*More cost-efficient because as a refrigerant itself, CO2 is cheap and worldwide available. The servicing of CO2 systems will be less costly and less complicated than that of present systems. For the consumer, the total cost of ownership is lowest with CO2 as it will significantly cut fuel consumption by the air conditioning device. Carmakers have to make an initial investment estimated at €20 per unit, with no additional costs once CO2 Technology enters into mass production.
*Usable in Heat Pumps because at least one CO2 system under development can act as a heat pump, supplying cabin heat and windshield defrosting even before the engine has warmed up.
*Although the Alliance may not mention it, since CO2 is so cheap and relatively harmless to the environment, the reservoirs in such systems could store additional liquid R744 to keep a vehicle cool even when the engine (or compressor) was not running.
*Technology is readily developed long ago. During the RACE Project from 1994 to 1997, financed by the EU with nearly 2 Million Euros, main producers of cars agreed to develop CO2 car AC systems. Se
The result was that car AC systems for CO2 small cars are 45% more expensive than HFKW Units and that for the luxury class the additional cost was irrelevant. There is a final presentation of the Project containing this data.
Arguments against CO2
CO2 Technology requires the design of completely new high-pressure systems whereas so-called "drop-in solutions" (the adaptation of current systems to new substances) are potentially more cost-efficient.
The Alliance for CO2 Solutions claims, however that the initial costs of CO2 systems will be around €5 higher than drop-in solutions and that over a car's life cycle, CO2 air conditioning systems will be more cost-efficient than any currently used or proposed new chemical blends. (see 2">#Arguments_for_CO2, Arguments for CO2).
has been classified as Safety Class A1 (low-toxic, non-flammable refrigerant) by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) – the highest safety class possible. As the charge of CO2 to the air conditioning systems is very small (200-400 g) there is no real danger for the passengers, even in case of accidental release.
Arguments for non-CO2 refrigerants
*Refrigerants such as the Greenpeace
Greenpeace is an independent global campaigning network, founded in Canada in 1971 by a group of Environmental movement, environmental activists. Greenpeace states its goal is to "ensure the ability of the Earth to nurture life in all its biod ...
-developed ' Greenfreeze', based on purified butane
Butane () is an alkane with the formula C4H10. Butane exists as two isomers, ''n''-butane with connectivity and iso-butane with the formula . Both isomers are highly flammable, colorless, easily liquefied gases that quickly vaporize at ro ...
/propane
Propane () is a three-carbon chain alkane with the molecular formula . It is a gas at standard temperature and pressure, but becomes liquid when compressed for transportation and storage. A by-product of natural gas processing and petroleum ref ...
mixtures, are entirely 'natural', and due to increased efficiency over refrigerants such as R134a
1,1,1,2-Tetrafluoroethane (also known as norflurane ( INN), R-134a, Klea 134a, Freon 134a, Forane 134a, Genetron 134a, Green Gas, Florasol 134a, Suva 134a, HFA-134a, or HFC-134a) is a hydrofluorocarbon (HFC) and haloalkane refrigerant with therm ...
, allow the use of very small amounts of refrigerant to be used.
*The use of pure hydrocarbon refrigerants, which are 'backward compatible' with even early Freon
Freon ( ) is a registered trademark of the Chemours Company and generic descriptor for a number of halocarbon products. They are stable, nonflammable, low toxicity gases or liquids which have generally been used as refrigerants and as aerosol p ...
(R-12) car air conditioning systems, would allow these systems to be easily converted (without modification), increasing their efficiency, and preventing further release of harmful R-134a and R-12 to the atmosphere.
Arguments against non-CO2 refrigerants
Butane and propane are very flammable petroleum products; they are used as fuels for gas barbecue
Barbecue or barbeque (often shortened to BBQ worldwide; barbie or barby in Australia and New Zealand) is a term used with significant regional and national variations to describe various cooking methods that employ live fire and smoke to coo ...
grills, disposable lighters, etc. Like gasoline, to which it chemically is closely related, propane tends to explode if mixed with oxygen and ignited in an enclosed container.
The use of highly flammable hydrocarbon gases such as butane and propane as automotive refrigerants raises serious safety concerns. The EPA, in evaluating motor vehicle air conditioning substitutes for CFC-12 (Freon, or R-12) under its SNAP program, has classified as "Unacceptable Substitutes" other "Flammable blend of hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...
s" because of "insufficient data to demonstrate safety." The EPA defines "Unacceptable" in this context as "illegal for use as a CFC-12 substitute in motor vehicle air conditioners". All of the refrigerants which the EPA approved for motor vehicle use in place of CFC-12 (as of 28 September 2006) contain no more than 4% of total flammable hydrocarbons (butane, isobutane, and/or isopentane). Therefore, it appears unlikely, for safety reasons, that EPA will approve 'Greenfreeze' or similar hydrocarbon-based refrigerants for automotive use.
History
In September 2007, the German Association of the Automotive Industry (VDA) officially announced its decision to use CO2 as the refrigerant in next-generation air conditioning. A working group at the European Automobile Manufacturers Association (ACEA) proposed drafting an industry-wide common position. Reports later claimed VDA members would avoid complying with the EU directive through legal loopholes.German TV explains car industry boycott of EU law
/ref>
Positions
* ttps://web.archive.org/web/20110719201533/http://www.greenpeace.de/themen/klima/nachrichten/artikel/vda_gegen_den_rest_der_welt/ Greenpeace Germany - News Release 6 September 2007br>Alliance for CO2 Solutions - Press Release 6 September 2007
Alliance for CO2 Solutions - Press Release 30 July 2007
Alliance for CO2 Solutions - Press Release 13 June 2007
* ttps://web.archive.org/web/20070930165229/http://www.umweltbundesamt.de/uba-info-presse-e/2007/pdf/pe07-027.pdf German Federal Environment Agency (Umweltbundesamt) - Press Release 8 May 2007
Media coverage
Spiegel-Online.de (06/09/2007)
ENDS Europe Report - August edition
*
References
External links
R744.com Website dedicated to CO2 Technology
Shecco.com
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{{Authority control
Heating, ventilation, and air conditioning
20th-century inventions
American inventions
Automotive cooling systems
Sustainable design