How does automotive air conditioning work?

The principle of operation is similar to ordinary conditioning devices, with the exception of the compressor which is driven by the vehicle engine. The condenser is forced convection, where a separate fan or the radiator fan is used, in which case the condenser is installed in front of the radiator. Air movement inside the vehicle is performed by a centrifugal fan coupled to the electric motor. As the compressor operates within the operating characteristics of the automobile engine, a suction regulating valve is installed in the return tube. The components of an automotive conditioning system are: compressor, condenser, evaporator, fan motor, thermostatic expansion valve, liquid reservoir, filter, magnetic switch and thermostat.

Como funciona o ar condicionado automotivo?

O princípio de funcionamento é semelhante aos aparelhos comuns de condicionamento, com exceção do compressor que é acionado pelo motor do veículo. O condensador é a convecção forçada, onde é usado um ventilador separado ou o próprio ventilador do radiador, sendo, neste caso, o condensador instalado na frente do radiador. O movimento do ar no interior do veículo é executado por um ventilador centrífugo acoplado ao motor elétrico. Como o compressor funciona dentro das características de funcionamento do motor do automóvel, uma válvula reguladora de sucção é instalada no tubo de retorno. Os componentes de um sistema de condicionamento automotivo são: compressor, condensador, evaporador, motor ventilador, válvula de expansão termostática, depósito de líquido, filtro, chave magnética e termostato. 

In cases of a 4-meter difference between the evaporator and condenser units of a split, the evaporator unit being at a lower level than it should be done?

A siphon must be installed in the suction line for every 3 meters of unevenness. In the installation where the evaporator unit is located and the condensing unit on the same level or the evaporator unit is at the upper level, a siphon followed by an inverted "U" must be installed immediately after the evaporator unit is discharged into the suction line. Should be in the same plane as the highest point on the evaporator.

Nos casos de diferença de 4 metros entre as unidades evaporadoras e condensadoras de um split, estando a unidade evaporadora em nível inferior a que deve-se fazer?

Deve ser instalado na linha de sucção um sifão para cada 3 metros de desnível. Na instalação em que estiverem a unidade evaporadora e a unidade condensadora no mesmo nível ou a unidade evaporadora estiver em nível superior, deve ser instalado logo após a saída da unidade evaporadora na linha de sucção, um sifão seguido de um “U” invertido, cujo nível superior do mesmo deve estar no mesmo plano do ponto mais alto do evaporador. 

What is the difference between direct and indirect expansion type evaporator?

In the direct expansion evaporator, it is the cooling fluid itself of the refrigeration system that carries out the final cooling process, ie the withdrawal of heat from the medium to be cooled. Thus, for example, in a window air conditioner, the ambient air, which is the medium to be cooled, comes into contact with the coil of the evaporator, inside which evaporates the cooling fluid from the cooling system. In the indirect expansion evaporator, there is a fluid intermediate the refrigerant in the refrigeration system, and the medium to be cooled. That is, the refrigerant in the refrigeration system will cool an intermediate fluid, and this fluid will remove heat from the medium to be cooled. So, for example, in a large chiller / fan-coil type air conditioning system, the chiller refrigerant gas (chiller) performs the water cooling, producing ice water. This cold water will cool the air in air-conditioned environments, in fan-coil

Qual a diferença entre evaporador do tipo expansão direta e indireta?

No evaporador de expansão direta, é o próprio fluido refrigerante do sistema de refrigeração que realiza o processo de resfriamento final, ou seja, a retirada de calor do meio que se quer resfriar. Assim, por exemplo, em um condicionador de ar de janela, o ar do ambiente climatizado, que é o meio que se quer resfriar, entra em contato com a serpentina do evaporador, por dentro da qual evapora o fluido refrigerante do sistema de refrigeração. No evaporador de expansão indireta, existe um fluido intermediário entre o refrigerante do sistema de refrigeração, e o meio que se quer resfriar. Ou seja, o refrigerante do sistema de refrigeração irá resfriar um fluido intermediário, e este fluido é que irá retirar calor do meio a ser resfriado. Então, por exemplo, em um sistema de condicionamento de ar de grande porte do tipo chiller/fan-coil, o gás refrigerante do sistema de refrigeração (chiller) realiza o resfriamento de água, produzindo água gelada. Esta água gelada é que irá resfriar o ar dos ambientes climatizados, no fan-coil.

Top Reasons Why Refrigeration Compressors Fail.

 The lubricating oil of the compressor, in some types of compressors, is pumped together with the refrigerant. If there is no return of this oil to the compressor, the lack of oil will cause the compressor to wear out quickly and its locking may occur.  The lubricating oil may react chemically with the refrigerant. This occurs when refrigerant and oil are chemically compatible, such as R-134a refrigerant and mineral oil. The oil may be "fine", i.e., has its viscosity reduced, which may also lead to the failure cited above.  The chemical reaction of the oil with the refrigerant also results in the formation of acids, which in turn chemically attack (react with) various compressor materials, such as the enamel covering the wiring of the electric motor, the rubbers, plastics and metals used On the compressor body, etc. Obviously, this chemical attack wears out and destroys the parts, which can lead to failures.  Moisture (water) can also react with the refrigerants and oils, forming acids, with the consequences described above. Hence the importance of a correct and effective dehydration of the system (obtained through the evacuation process).  The intake of liquid refrigerant in the compressor can also cause faults. If the liquid is sucked by the compressor pump, it can reach the suction valves, causing an erosion (called liquid stroke) that eventually leads to valve breakage, rendering the compressor ineffective or even arresting it.  When the compressor is subjected to high pressure differentials (difference between the suction pressure and the compressor discharge pressure), it needs to expend much more energy to pump the refrigerant. When this occurs, the electric motor that moves the compressor begins to consume much more electric energy, which is translated by the increase of the current in the compressor. For this there is the overload protection relay: if the current in the compressor increases greatly, this relay automatically shuts off the compressor. However, in case of relay failure, or in the case of using an inadequate (over-sized) relay, the relay may not turn off the compressor, which may lead to an electric motor burnout (motor wiring overheats, enamel Protector around the wire is destroyed, and the wiring may short circuit).  When the compressor discharge temperature is too high, the compressor as a whole overheats, which increases the possibility of chemical reactions between moisture, refrigerant and lubricating oils, and may also cause degradation of the electric motor materials. Lead to burning.  When the compressor is switched off, liquid refrigerant may migrate from the suction line to the compressor housing or crankcase. This liquid refrigerant mixes with the oil. This can cause the oil to lose part of its lubricating capacity, becoming "thin", which, when the compressor is reconnected, will end up causing more wear on the compressor.