This is a repost from Wikipedia Automobile air conditioning (also called A/C) systems use air conditioning to cool the air in a vehicle. History A company in New York City in the United States first offered installation of air conditioning for cars in 1933. Most of their customers operated limousines and luxury cars. In 1939, Packard became the first automobile manufacturer to offer an air conditioning unit in its cars. These were manufactured by Bishop and Babcock Co, of Cleveland, Ohio. The “Bishop and Babcock Weather Conditioner” also incorporated a heater. Cars ordered with the new “Weather Conditioner” were shipped from Packard’s East Grand Boulevard facility to the B&B factory where the conversion was performed. Once complete, the car was shipped to a local dealer where the customer would take delivery. Packard fully warranted and supported this conversion, and marketed it well. However, it was not commercially successful for a number of reasons: ⦁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 ⦁It was superseded by more efficient systems in the post-war years.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 remedy this problem.) ⦁The several feet of plumbing going back and forth between the engine ⦁ compartment and trunk proved unreliable in service. ⦁The price, at US $274 ($4,692.12 in 2014 US dollars), was unaffordable to most people in post-depression/pre-war America. The option was discontinued after 1941. The 1953 Chrysler Imperial was one of the first production cars in twelve years to offer modern automobile air conditioning as an option, following tentative experiments by Packard in 1940 and Cadillac in 1941. Walter Chrysler had seen to the invention of Airtemp air conditioning in the 1930s for the Chrysler Building 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, and Oldsmobile added air conditioning as an option on some of their models in the 1953 model year. All of these Frigidaire systems used separate engine and trunk mounted components. Logo on a 1957 car with AMC factory installed air-conditioning system In 1954, the Nash Ambassador was the first American automobile to have a 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 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” 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 it’s $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 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.” Air-conditioning for automobiles came into wide use from the late twentieth century. 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 of a vehicle. Factors such as wind resistance, aerodynamics and engine power and weight 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. The innovation was adopted quickly and new features to air conditioning like the Cadillac Comfort Control which was a completely automatic heating and cooling system set by dial thermostat was introduced as an industry first in the 1964 model year. 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 domestic automobiles were equipped with air conditioning, with the feature needed not only for passenger comfort but also to increase the car’s resale value. A car cooler A car cooler is an automobile window-mounted evaporative cooler, sometimes referred to as a swamp cooler. It was an early type of automobile air conditioner and is not used in modern cars. To cool the air it used latent heat (in other words, cooling by water evaporation). Water inside the cooler evaporates and in the process transfers heat from the surrounding air. The cool moisture-laden air is directed to the inside of the car. The lower the humidity, the better the system works. Because of the dry desert air, car coolers were popular in the southwestern United States states of California, Arizona, Texas, New Mexico, and Nevada. Chrysler Airtemp The 1953 Chrysler Imperial was one of the first production cars in twelve years to offer modern automobile air conditioning as an option, following tentative experiments by Packard in 1940 and Cadillac in 1941. Walter Chrysler had seen to the invention of Airtemp air conditioning in the 1930s for the Chrysler Building 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, and Oldsmobile added air conditioning as an option on some of their models in the 1953 model year. All of these Frigidaire systems used separate engine and trunk mounted components. Growth in demand Air-conditioning for automobiles came into wide use from the late twentieth century. 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 of a vehicle. Factors such as wind resistance, aerodynamics and engine power and weight 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. Evaporative cooling A car cooler A car cooler is an automobile window-mounted evaporative cooler, sometimes referred to as a swamp cooler. It was an early type of automobile air conditioner and is not used in modern cars. To cool the air it used latent heat (in other words, cooling by water evaporation). Water inside the cooler evaporates and in the process transfers heat from the surrounding air. The cool moisture-laden air is directed to the inside of the car. The lower the humidity, the better the system works. Because of the dry desert air, car coolers were popular in the southwestern United States states of California, Arizona, Texas, New Mexico, and Nevada. Operating principles See also: Refrigeration cycle A simple stylized diagram of the refrigeration cycle: 1) condensing coil, 2) expansion valve, 3) evaporator coil, 4) compressor In the refrigeration cycle, heat is transported from the passenger compartment to the environment. A refrigerator is an example of such a system, as it transports the heat out of the interior and into its environment (i.e. the room). Circulating refrigerant gas vapor enters the gas compressor in the engine bay 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 through the condenser coils and condensed into a liquid. Thus, the circulating refrigerant rejects heat from the system and the heat is carried away by air. The condensed and pressurized liquid refrigerant is next routed through a thermal expansion valve where it undergoes an abrupt reduction in pressure. That pressure reduction results in flash evaporation of a part of the liquid refrigerant, lowering its temperature. The cold refrigerant is then routed through the evaporator coil in the passenger compartment. The air (which is to be cooled) blows 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. To complete the refrigeration cycle, the refrigerant vapor is routed back into the compressor. The compressor can be driven by the car’s engine (e.g. via a belt) or by an electric motor. Power consumption In a modern automobile, the A/C system will use around 4 horsepower (3 kW) of the engine’s power, thus increasing fuel consumption of the vehicle. source – Wikipedia ]]>
Automotive Air Conditioning (The History)
Typical A/C system[/caption]
The High-pressure Side
All automotive air conditioning systems are (nearly) closed loops with a high-pressure side and low-pressure side. We’ll start with the high-pressure side as it leads from the engine to the passenger compartment.
Compressor: The compressor is a pump driven by a belt attached to the engine’s crankshaft. When the refrigerant is drawn into the compressor, it is in a low-pressure gaseous form. Once the gas is inside the pump, the compressor lives up to its name. The belt drives the pump, which puts the gas under pressure and forces it out to the condenser. Compressors cannot compress liquids, only gasses. You’ll see as we go through the system that there are other parts whose job it is to capture any water that accidentally makes into the AC loop.
Condenser: The condenser is basically a radiator, and it serves the same purpose as the one in your car: to radiate heat out of the system. The refrigerant enters the condenser as a pressurized gas from the compressor. The process of pressurizing the gas and moving it to the condenser creates heat, but air flowing around the twisting tubes of the condenser cools the refrigerant down until it forms a liquid again. Imagine steam cooling down and condensing back into water, and you’ve got the idea. The liquid refrigerant is now a high-pressure liquid and nearly ready to cool the car.
Receiver-Dryer: But first, the refrigerant needs to be prepped for the evaporator. As it moves out of the condenser, the liquid goes through a little reservoir installed in the line. This receiver-dryer contains desiccants, small granules that attract water. You’ve seen packets of desiccants in shoeboxes, where they do the same thing: attract water from the air to keep new shoes fresh and ready for your feet. (They’re usually labeled “Do not eat.”) In the receiver-dryer, they remove any water that has entered the system. If the water is allowed to remain and possibly form ice crystals, it can damage the air conditioning system.
That’s enough high-pressure for anyone, so let’s move on to the low-pressure side of the system.
The Low-pressure Side
Thermal Expansion Valve (TXV): Here, the system changes from the high-pressure side to the low-pressure side. If you were to touch this part of the system, you’d feel it change from hot to cold.
The high-pressure liquid refrigerant flows from the receiver-dryer through the expansion valve, where it is allowed to expand. This expansion reduces the pressure on the refrigerant, so it can move into the evaporator. The valve senses pressure and regulates the flow of refrigerant, which allows the system to operate steadily, but the moving parts of the valve can wear out and sometimes require replacement.
Some vehicles have an orifice tube rather than an expansion valve, but it serves the same purpose in allowing the refrigerant to expand and the pressure to be lowered before the liquid enters the evaporator. The orifice tube allows refrigerant to flow at a constant rate and has no moving parts, but it can become clogged with debris over time. Systems with an orifice tube automatically turn the AC system on and off to regulate the flow of refrigerant to the evaporator.
Evaporator: This is where the magic happens. While all the other parts of the system are located in the engine compartment, this one is in the cabin, usually above the footwell on the passenger side. It also looks like a radiator, with its coil of tubes and fins, but its job is to absorb heat rather than dissipate it.
Refrigerant enters the evaporator coil as a cold, low-pressure liquid, ideally at 32 degrees Fahrenheit (0 degrees Celsius), which is why you don’t want any water in the system. The refrigerant doesn’t freeze at this temperature, but it does have a very low boiling point. The heat in the cabin of the car is enough to make the R-134a in the evaporator boil and become a gas again, just like water turning back to steam. In its gaseous form, the refrigerant can absorb a lot of heat.
The gas moves out of the evaporator — and out of the passenger compartment of the car, taking the heat with it. A fan blowing over the outside of the evaporator coil blows cool air into the passenger compartment. The refrigerant in gas form then enters the compressor, where it is pressurized and the whole process starts all over again.
If the system uses an orifice tube, there will be an accumulator between the evaporator and the compressor. An orifice tube sometimes lets too much refrigerant into the evaporator and it doesn’t all boil. Since the compressor cannot compress liquid, only gas, the accumulator traps any excess liquid before it can get into the compressor.
The evaporator also takes humidity out of the air in the car, which helps you feel cool. Water in the air condenses on the evaporator coil, along with dirt and pollen and anything else floating around in the cabin. When you stop the car and see water dripping underneath, it’s probably the water from the AC evaporator and nothing to worry about.
We’ve all heard about “recharging the A/C,” so we’ll take a quick look at that next.
Recharging a Car’s A/C
Most of us start seeing ads in the spring for car repair shops offering deals on recharging your car’s air conditioning in time for the coming summer. Which makes us ask, what is recharging the A/C? Is it required, like an oil change? Does my car’s air conditioning need to be recharged? Is this another scam that repair shops can pull on unsuspecting customers?
The answer to that last one is definitely no; recharging the A/C is not a scam. It simply means that fresh refrigerant is added to the system. If the refrigerant is a bit low, it can be topped off, the same as if you were a bit low on oil in the engine. If it’s really low, though, whatever refrigerant is still in the system needs to be drained out and replaced. This process of clearing out the system and adding new fluid is called recharging.
In either case, you’ve lost some refrigerant, which isn’t so great. Even though R-134a is better for the environment than Freon, the Environmental Protection Agency would rather not have any air conditioning refrigerant leaking into the soil and rivers. If you’re going to have the system drained and recharged, the EPA recommends having the technician take a look at the system to find the source of the leak and fix it. They don’t require the repair, but they’d really, really like you to have it done.
This article has talked a lot about R-134a as a replacement for big, bad Freon, but there are others that have been approved by the EPA, too. R-134a has the distinction of being the refrigerant most tested and recommended by manufacturers, but there are others with names like Free Zone, Freeze 12, and Kar Kool that the EPA will allow in automotive air conditioning systems.