Automobile air conditioning

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1953 Chrysler Imperial with factory trunk mounted "Airtemp" system 1953 Imperial 2-tone with AC vents.jpg
1953 Chrysler Imperial with factory trunk mounted "Airtemp" system

Automobile air conditioning (also called A/C) systems use air conditioning to cool the air in a vehicle.

Contents

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. [1]

In 1939, Packard became the first automobile manufacturer to offer an air conditioning unit in its cars. [2] These bulky units were manufactured by Bishop and Babcock (B&B), of Cleveland, Ohio and ordered on approximately 2,000 cars. [3] 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 conversion 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 option was discontinued after 1941. [3]

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. [4] 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. [4]

Cadillac, Buick, and Oldsmobile added air conditioning as an option on some of their models in the 1953 model year. [5] All of these Frigidaire systems used separate engine and trunk mounted components. [6] [7]

Nash integrated system

Logo on a 1957 car with AMC factory installed air-conditioning system 1957 Rambler Custom Cross-Country wagon AnnMD-i.jpg
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. [8] [9] 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. [10] This was the first mass market system with controls on the dash and an electric clutch. [11] This system was also compact and serviceable with all of its components installed under the hood or in the cowl area. [12]

Combining heating, cooling, and ventilating, the new air conditioning system for the Nash cars was called the "All-Weather Eye". [13] This followed the marketing name of "Weather Eye" for Nash's fresh-air automotive heating and ventilating system that was first used in 1938. [12] With a single thermostatic control, the Nash passenger compartment air cooling option was "a good and remarkably inexpensive" system. [14] The system had cold air for passengers enter through dash-mounted vents. [15] Nash's exclusive "remarkable advance" was not only the "sophisticated" unified system, but also its $345 price that beat all other systems. [16]

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. [17] It was very expensive and not a fully integrated system with separate controls and ducts for air distribution. [18] [19] The heater core continued to be a separate "Venti-Seat" or under the front seat system with its own controls. [20] 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." [21]

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.

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. [22] 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. [23] 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. [24] [25] 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. [26]

Evaporative cooling

A car cooler 1949 Hudson Commodore 8 four-door with Kool Air at 2015 Macungie show 3of4.jpg
A car cooler

A car cooler is an automobile evaporative cooler, sometimes referred to as a swamp cooler. [27] [28] Most are aftermarket relatively inexpensive accessories consisting of an external window-mounted metal cylinder without moving parts, but internal under dashboard or center floor units with an electric fan are available. [29] [30] It was an early type of automobile air conditioner [31] and is not used in modern cars relying on refrigerative systems to cool the interior.

To cool the air it used latent heat (in other words, cooling by water evaporation). [32] 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. [32] [33] The evaporate "cooling" effect decreases with humidity because the air is already saturated with water. Therefore, the lower the humidity, 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. [30]

Operating principles

A simple stylized diagram of the refrigeration cycle: 1) condensing coil, 2) expansion valve, 3) evaporator coil, 4) compressor Heatpump.svg
A simple stylized diagram of the refrigeration cycle: 1)  condensing coil, 2)  expansion valve, 3)  evaporator coil, 4)  compressor
Regassing the air conditioning of a Ford Focus. Regassing the aircon of a Ford Focus 2017 04.jpg
Regassing the air conditioning of a Ford Focus.

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 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 in the engine bay, usually an axial piston pump 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 rejects heat from the system and the heat is carried away by the air.

In a thermal expansion valve 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 in order to remove any residual water content (which would become ice inside the expansion valve and therefore clog it) that the vacuum done prior to the charging process didn't manage to remove from the system, and filters it in order 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 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's known as an accumulator. In such an air conditioning system, the accumulator also prevents liquid refrigerant from reaching the compressor during low cooling demand periods.

The air, often after being filtered by a cabin air filter, is blown by an adjustable speed electric powered centrifugal fan 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, is precisely regulating the centrifugal fan speed so that only the strictly required volumetric flow rate of air is cooled by the evaporator. The user is also given the option to close the vehicle's external air flaps, in order to achieve even faster and stronger cooling by recirculating the already cooled air inside the cabin to the evaporator. Finally, whenever the compressor is able to 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 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 either 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, 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 is 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, 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.

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. [34]

See also

Related Research Articles

Refrigeration Process of moving heat from one location to another in controlled conditions

Refrigeration is a process that removes heat from a space, substance, or system to lower and/or maintain its temperature below the ambient temperature. In other words, refrigeration is artificial (human-made) cooling. Energy in the form of heat is removed from a low-temperature reservoir and transferred to a high-temperature reservoir. The work of energy transfer is traditionally driven by mechanical means, but can also be driven by heat, magnetism, electricity, laser, or other means. Refrigeration has many applications, including household refrigerators, industrial freezers, cryogenics, and air conditioning. Heat pumps may use the heat output of the refrigeration process, and also may be designed to be reversible, but are otherwise similar to air conditioning units.

Heating, ventilation, and air conditioning Technology of indoor and vehicular environmental comfort

Heating, ventilation, and air conditioning (HVAC) is the technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics and heat transfer. "Refrigeration" is sometimes added to the field's abbreviation, as HVAC&R or HVACR or "ventilation" is dropped, as in HACR.

Heat pump Pumps heat backward - a device that transfers thermal energy in the opposite direction of spontaneous heat transfer

A heat pump is a device that transfers heat energy from a source of heat to what is called a thermal reservoir. Heat pumps move thermal energy in the opposite direction of spontaneous heat transfer, by absorbing heat from a cold space and releasing it to a warmer one. A heat pump uses external power to accomplish the work of transferring energy from the heat source to the heat sink. The most common design of a heat pump involves four main components – a condenser, an expansion valve, an evaporator and a compressor. The heat transfer medium circulated through these components is called refrigerant.

Intercooler specific type of mechanical device used to cool liquid or gas

An intercooler is a mechanical device used to cool a gas after compression. Compressing a gas increases its internal energy which in turn raises its temperature and reduces its density. An intercooler typically takes the form of a heat exchanger that removes waste heat in a gas compressor. Intercoolers have a variety of applications, and can be found in air compressors, air conditioners, refrigeration, and gas turbines, and automotive engines, for example. They are widely known as an air-to-air or air-to-liquid cooler for forced induction internal combustion engines, used to improve volumetric efficiency. This is accomplished by increasing intake air density through nearly constant pressure cooling.

Refrigerant substance or mixture, usually a fluid, used in a heat pump and refrigeration cycle

A refrigerant is a substance or mixture, usually a fluid, used in a heat pump and refrigeration cycle. In most cycles it undergoes phase transitions from a liquid to a gas and back again. Many working fluids have been used for such purposes. Fluorocarbons, especially chlorofluorocarbons, became commonplace in the 20th century, but they are being phased out because of their ozone depletion effects. Other common refrigerants used in various applications are ammonia, sulfur dioxide, and non-halogenated hydrocarbons such as propane.

An evaporative cooler is a device that cools air through the evaporation of water. Evaporative cooling differs from typical air conditioning systems, which use vapor-compression or absorption refrigeration cycles. Evaporative cooling uses the fact that water will absorb a relatively large amount of heat in order to evaporate. The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapor (evaporation). This can cool air using much less energy than refrigeration. In extremely dry climates, evaporative cooling of air has the added benefit of conditioning the air with more moisture for the comfort of building occupants.

Chiller machine that removes heat from a liquid via a vapor-compression or absorption refrigeration cycle

A chiller is a machine that removes heat from a liquid via a vapor-compression or absorption refrigeration cycle. This liquid can then be circulated through a heat exchanger to cool equipment, or another process stream. As a necessary by-product, refrigeration creates waste heat that must be exhausted to ambience, or for greater efficiency, recovered for heating purposes. Chillers may use hermetic scroll, or semi hermetic screw, or centrifugal compressors.

Refrigerator Compartment used to store food or other items at low temperatures for preservation

A refrigerator consists of a thermally insulated compartment and a heat pump that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the room temperature. Refrigeration is an essential food storage technique in developed countries. The lower temperature lowers the reproduction rate of bacteria, so the refrigerator reduces the rate of spoilage. A refrigerator maintains a temperature a few degrees above the freezing point of water. Optimum temperature range for perishable food storage is 3 to 5 °C. A similar device that maintains a temperature below the freezing point of water is called a freezer. The refrigerator replaced the icebox, which had been a common household appliance for almost a century and a half.

Icemaker consumer device for making ice, found inside a  freezer

An icemaker, ice generator, or ice machine may refer to either a consumer device for making ice, found inside a home freezer; a stand-alone appliance for making ice, or an industrial machine for making ice on a large scale. The term "ice machine" usually refers to the stand-alone appliance.

Absorption refrigerator Single pressure absorption refrigeration

An absorption refrigerator is a refrigerator that uses a heat source to provide the energy needed to drive the cooling process. The system uses two coolants, the first of which performs evaporative cooling and is then absorbed into the second coolant; heat is needed to reset the two coolants to their initial states. The principle can also be used to air-condition buildings using the waste heat from a gas turbine or water heater. Using waste heat from a gas turbine makes the turbine very efficient because it first produces electricity, then hot water, and finally, air-conditioning—trigeneration. Absorption refrigerators are commonly used in recreational vehicles (RVs), campers, and caravans because they can be powered with propane fuel, rather than electricity. Unlike more common vapor-compression refrigeration systems, an absorption refrigerator can be produced with no moving parts other than the coolants.

Economizers, or economisers (UK), are mechanical devices intended to reduce energy consumption, or to perform useful function such as preheating a fluid. The term economizer is used for other purposes as well. Boiler, power plant, heating, refrigeration, ventilating, and air conditioning (HVAC) uses are discussed in this article. In simple terms, an economizer is a heat exchanger.

Vapour-compression refrigeration or vapor-compression refrigeration system (VCRS), in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and is the most widely used method for air-conditioning of buildings and automobiles. It is also used in domestic and commercial refrigerators, large-scale warehouses for chilled or frozen storage of foods and meats, refrigerated trucks and railroad cars, and a host of other commercial and industrial services. Oil refineries, petrochemical and chemical processing plants, and natural gas processing plants are among the many types of industrial plants that often utilize large vapor-compression refrigeration systems. Cascade refrigeration systems may also be implemented using 2 compressors.

Weather Eye Worlds first mass-market automotive heating, ventilation and air conditioning (HVAC) system

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 market. The use of the Weather Eye name for automobile passenger heating and air conditioning systems continued in American Motors (AMC) vehicles.

Thermal expansion valve component of air conditioning and refrigeration systems

A thermal expansion valve or thermostatic expansion valve is a component in refrigeration and air conditioning systems that controls the amount of refrigerant released into the evaporator thereby keeping superheat, that is, the difference between the current refrigerant temperature at the evaporator outlet and its saturation temperature at the current pressure, at a stable value, ensuring that the only phase in which the refrigerant leaves the evaporator is vapor, and, at the same time, supplying the evaporator's coils with the optimal amount of liquid refrigerant to achieve the optimal heat exchange rate allowed by that evaporator. In addition, some thermal expansion valves are also specifically designed to ensure that a certain minimum flow of refrigerant can always flow through the system. Thermal expansion valves are often referred to generically as "metering devices" although this may also refer to any other device that releases liquid refrigerant into the low-pressure section but does not react to temperature such as a capillary tube or a pressure-controlled valve.

Air conditioning Process of altering the properties of air to more favorable conditions

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

Heat pump and refrigeration cycle Mathematical models of heat pumps and refrigeration

Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pumps and refrigerators. A heat pump is a mechanical system that allows for the transference of heat from one location at a lower temperature to another location at a higher temperature. Thus a heat pump may be thought of as a "heater" if the objective is to warm the heat sink, or a "refrigerator" if the objective is to cool the heat source. In either case, the operating principles are identical. Heat is moved from a cold place to a warm place.

A direct exchange (DX) geothermal heat pump is a type of geothermal heat pump in which refrigerant circulates through copper tubing placed in the ground. It is a closed-loop, refrigerant-based geothermal system.

Free cooling is an economical method of using low external air temperatures to assist in chilling water, which can then be used for industrial processes, or air conditioning systems. The chilled water can either be used immediately or be stored for the short- or long-term. When outdoor temperatures are lower relative to indoor temperatures, this system utilizes the cool outdoor air as a free cooling source. In this manner, the system replaces the chiller in traditional air conditioning systems while achieving the same cooling result. Such systems can be made for single buildings or district cooling networks.

Radiator (engine cooling) heat-exchanging component of liquid cooled engines

Radiators are heat exchangers used for cooling internal combustion engines, mainly in automobiles but also in piston-engined aircraft, railway locomotives, motorcycles, stationary generating plant or any similar use of such an engine.

The term subcooling also called undercooling refers to a liquid existing at a temperature below its normal boiling point. For example, water boils at 373 K; at room temperature (293 K) the water is termed "subcooled". A subcooled liquid is the convenient state in which, say, refrigerants may undergo the remaining stages of a refrigeration cycle. Normally, a refrigeration system has a subcooling stage, allowing technicians to be certain that the quality, in which the refrigerant reaches the next step on the cycle, is the desired one. Subcooling may take place in heat exchangers and outside them. Being both similar and inverse processes, subcooling and superheating are important to determine stability and well-functioning of a refrigeration system.

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