Automobile air conditioning

The first fully functional air conditioning system according to the current principle to have been invented by WHCarrier 1911. In the area of car air conditioners, these were also built by Studebaker first in 1938 by Nash, and in the same year. The basic structure is essentially unchanged since then, the control and expression, however, have continued to improve. In the upper class segment air conditioners were to be found in large numbers only since the late 1960s, today they belong to the standard scope of modern vehicles.

Air conditioners cool the fresh air flowing into the car or - if the air recirculation switch is operated ( eg what is recommended in long tunnels ) - the air inside. In both cases, the air in the cooling and moisture is removed. This helps especially in the cool season helps to dry from the inside fogged windows. This in turn contributes to the visibility and therefore to road safety.

General

Air conditioners are also used in aircraft and motor vehicles. Frequently they also climate control ( Climatronic) or automatic climate control is spoken. The general difference is in the operating mode and / or Ansprechart the components of the air conditioning. A climate control (Climatic ), and automatic climate control are controlled electronically with different features, on the other hand does the older systems control via rotary switch or slider, this is referred to as " manual " air conditioning. This distinction is whether the control is carried out as the forwarding setting mechanically (eg via Bowden cables ) or electrically (via power cables to motors). The automatic climate control systems in some vehicles allow separate adjustment of temperature on the driver and front passenger (some can also be in the backseat choose your own temperature). Rather hochklassigere vehicles allow, besides the setting for the desired interior temperature, the separate adjustment of air distribution and air flow.

Some systems use a Sun sensor (also: solar sensor). This determines the direction of incidence and angle of the sun, resulting in a cooling of the relevant side of the vehicle or of the entire vehicle interior, to compensate for the heat input in the sun.

Function

An air conditioner works like a refrigerator. In a medium heat exchanger is cooled by an artificial and continuously produced evaporation process. In everyday use, this effect is, for example, experienced when emptying a spray can, with the resulting evaporative cooling of the propellant of aerosol extracts heat and it cooled. This effect is continuously generated in the air conditioner using a refrigerant in a closed system.

The standing in a closed loop and high-pressure liquid refrigerant is depressurized by an expansion valve (2 ) into a space at lower pressure. In this case, the liquid refrigerant is injected into the evaporator, it can expand and change the state of aggregation to a gas. The corresponding component will be referred to as an evaporator (3) and is installed generally in the blow box, behind the instrument panel. The expansion valve is thus the place where the refrigerant is expanded in the evaporator and to cool it. The refrigerant has a rather low boiling point (about -23 ° C ) and evaporated here even at low temperatures. The air to be cooled for the interior is now externally directed past the fins of the evaporator fan in the box. The time required for the evaporation process of the refrigerant in the evaporator heat is extracted from the passing air and cools it noticeably. Simultaneously, the air is also removed moisture through condensation, because cold air can contain as much moisture as warm. The cooled and dried air is then directed through the air outlet into the vehicle interior. The resulting condensate to the fins of the evaporator is passed through a hose to the outside. Thus, pools of water explained by condensation under parked vehicles.

The gas has been cleared by the evaporation in the evaporator refrigerant now passes to the compressor (4). This represents the heart of an air conditioning system, and provides for the transport of refrigerant in the system. The driven by belt drive from the vehicle engine is usually compressor sucks the refrigerant gas and compresses it greatly (about 15 bar ) while the temperature of the coolant rises to about 56 ° C).

Thereafter, the compressed, gaseous and hot refrigerant gas is cooled in a downstream condenser (1). Since the refrigerant as any other fabric when liquefying heat is removed, the capacitor must deliver this heat to a cooling medium surrounding it. Therefore, this is installed standing normally in front of the vehicle cooler in the wind and this is similar in appearance and size. In general, this is supplemented by a fan to eg to provide the necessary heat dissipation in a traffic jam. In the condenser, the refrigerant is cooled. Here, the dew point of the coolant is exceeded, it liquefies again. The heat generated in the capacitor is similar to the vehicle radiator, usually discharged to the outside air.

Before the refrigerant again reaches the evaporator, the refrigerant optionally entrained moisture and impurities (for example, wear debris from the compressor ), extracted in a filter drier. The cleaned and liquefied refrigerant is passed again to the expansion valve. Here, the liquid refrigerant is injected into the evaporator. Finally, the artificial cycle of evaporation and compression of the refrigerant continues again.

Effect

Comfort and safety

The side effect that prevents fogging in turning on the air conditioning lies in the fact that colder air can in principle contain less moisture than warmer. Smaller pools of water under the car when parking due to the chilled air by lowering the dew point resulting humidity in the form of water as well as iced evaporator by " Defrosting" the evaporator of the air conditioning.

By air conditioning, an increased comfort is often perceived, thus also encouraging safety. In particular, at high temperatures, the concentration of the driver decreases considerably. Previously dismissed as a dispensable luxury, experienced automotive air conditioning systems in Germany in the 1990s, a boom. Today, the air conditioning is in the car as standard and does not provide only for cool, but also for clean air in the passenger compartment through an appropriate filter. Is cleaned the air by means of a cabin air filter, also known under the names of pollen or cabin filter. Only by using high quality cabin air filter systems to protect passengers from pollen, diesel soot, particulate matter, ozone and other irritant gases succeed. In certain classes of vehicles is now considered a used vehicle without air conditioning even as virtually unsaleable.

Colds by operation of air conditioning systems

Sometimes is the talk of the passengers of the opinion are to have contracted a cold in the vehicle by the operation of an air conditioner. The traditional and still widespread assumption colds would regularly only by cold - in the scientific sense of heat extraction as a pathophysiological mechanism - causing or cold cause or shapes such as drafts, moisture, hypothermia, is not correct. When operating an air conditioning system of the incoming air is withdrawn from moisture. Therefore, the mucous membranes tend in the ear, nose and throat likely to dry out. Under these conditions more easily bacteria can then colonize the parched mucous membranes, which may favor a viral infection. You should keep in air-conditioned vehicles to proper hydration. Furthermore, regular disinfection and filter change is recommended in the maintenance of an air conditioner.

More consumption

The compression of the refrigerant gas required performance. The operation of the air compressor, therefore, increases the working resistance of the motor and thus the consumption. The additional fuel consumption is largely independent of the rate and is between 0.2 and 0.5 liters per hour. The absolute increase in consumption per kilometer driven is thus dependent on the speed, the percentage addition from the average consumption.

Various consumer protection organizations advocate expel the excess consumption by the air conditioning in the vehicle data.

Retrofitting

Air conditioners can also be retrofitted. The cost for this is often considerable, since often the dash must be removed to install the evaporator can. The use of CFC refrigerants such as R12 (Freon ) has long been prohibited. The art is the use of fluorinated hydrocarbon R134a. For replacement of R12 in old air conditioners, however, is the mixture R413a, which consists only of 88% R134a, R134a, in contrast to similar flow and lubricating properties such as R12 has.

Maintenance

Air conditioning in the car are not maintenance -free. Many car owners do not know this. Refrigeration systems in motor vehicles have coolant losses, which are caused by the installation of " Open compressor ". The losses are primarily caused by leaking compressor shaft seals. Favors the leakage when the compressor is not turned on in the winter and the shaft seal is not supplied to the oil. In addition, possible leaks in detachable connections, which can be caused by vibrations (engine and road). The system should be checked approximately every two to four years for any loss of refrigerant; at the latest when the cooling performance decreases. When opening the investment of replacing the filter drier is recommended.

Refrigerant

With the MAC Directive of the EU ( ( 2006/40/EC ) of 2006 prohibits the use of these HFCs with a GWP greater than 150 ( this includes R134a) in air conditioners newly authorized types of vehicles from 31 December 2011. Should in future instead, get carbon dioxide (R744 ) is used. it has an award- lower global warming potential than conventional refrigerant (GWP of 1) and does not contribute to ozone depletion. Moreover, it was during test drives in almost all cases, a higher energy efficiency than R134a. Opting for CO2 ( R744) has been on the so-called " green" IAA 2007 by the Association President of the automotive manufacturers (VDA ), Matthias Wissmann announced as a joint result. on the eve of yet BMW issued a press release to intend to deliver the first production car with this technology worldwide. refrigeration components for the necessary high-pressure systems have been developed. Some car manufacturers were promoting the dangerous 2,3,3,3 - Tetrafluoropropene (trade name R1234yf ), since this can also use in the existing air conditioning systems. This fabric is relatively climate- friendly but flammable and is used worldwide by only two U.S. manufacturers produced (DuPont and Honeywell). When extinguishing tests after an accident can result in dangerous hydrofluoric acid. In September 2012, Mercedes announced that it will not use the refrigerant R1234yf due to its flammability on. Already this to fill vehicles are being recalled in the workshops. The filling is replaced with R134a. Despite the current ban, the EU Commission has issued an exemption that allowed the continued use of R134a until 31 December 2012. The reason for this is in stark delivery delay of the two main manufacturers for the new refrigerant R1234yf. With air as the refrigerant of the simple structure Schukey engine works.

Infringement proceedings against Germany

Following several months of pilot process, the EU launched on 23 January 2014 infringement proceedings against Germany because the back filling of an approved with new refrigerant R1234yf vehicle on the old refrigerant R134a is just as illegal as the admission of new vehicles as an extension to the old existing vehicle type-approvals. The infringement procedure is the first step, the result of the action of Germany in connection with a wide variety of vehicle type-approvals Daimler company. Other cases in other Member States (eg UK, Belgium and Luxembourg ) are part of the EU also investigated.