The climate control system offers both air conditioning and heating, because it regulates the environmental conditions in the passenger compartment, controlling the quantity, temperature and humidity of the air generated.
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Climate control system
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Nowadays, climate control is no longer considered as optional or luxury, but as standard vehicle equipment, and over 80% of vehicles on the road are fitted with it.
An increase in glazed surface and longer journey times are some of the reasons why climate control is now more important than ever before in terms of on-board comfort. In winter it assists with rapid demisting, controlling the humidity level in the passenger compartment to improve visibility and driving safety. Thanks to the passenger compartment filters, even the quality of the air generated in the passenger compartment is now better than ever before.
The climate control is a closed system, which acts upon differences in pressure and the change in state which the coolant gas undergoes throughout the circuit.There are many components involved:
Once the cycle is complete, the coolant is once again aspirated by the compressor. All of the components are connected by rigid piping.
The climate control system is also supported by two motor-driven fans: one radiator fan assembly and one passenger compartment fan assembly.
Before entering the vehicle via the air vents, the air passes through the passenger compartment filter which removes polluting particles and, in the case of active carbon filters, also harmful gases and unpleasant odours.
The compressor is the heart of the climate control system.Its function is to compress the coolant gas, transporting it from low pressure and low temperature to high pressure and high temperature. It is a precision component, and its quality has a significant impact in terms of safety, comfort and energy saving.
The compressor contains moving parts, therefore it must be appropriately lubricated using a specific oil, with the correct characteristics for the cooling system:
The condenser is a heat exchanger which cools and liquefies the coolant gas coming from the compressor. It is made up mainly of tubes (the primary exchange surface) and fins (the secondary exchange surface). The condenser is located at the front of the vehicle, in front of or next to the radiator.
The condenser transfers heat to the environment, because its temperature is higher than the surrounding one. The air passes through the condenser fin, and, by removing heat, causes the cooling fluid to liquefy.
Under normal usage conditions, the condenser does not need to be replaced throughout the vehicle's lifetime. Given its position, however, it can be easily damaged in the case of a front impact.
The use of sub cooling modules is on the increase, which as well as offering a condensing function, also act as a drier.
In the climate control system, there may be two different types of filter, depending on if the system is dry or wet. These, respectively, are the drier filter and the accumulator filter. If not already integrated into the condenser, the drier filter is located between the condenser and the expansion valve. The coolant passes through the drier filter in its liquid state at high pressure.
It has two main functions:
The presence of humidity in the circuit may prove fatal for the compressor, which does not tolerate the presence of liquids which are incompressible by nature. The evaporator may also be damaged, due to the acid which is created when the coolant comes into contact with water.
The accumulator used in wet systems is installed between the evaporator and the compressor, and is passed through by the coolant at low pressure.In short, the only thing to reach the compressor must be the coolant in its gaseous state.
To prevent damp air from penetrating the filters during storage, the filters are fitted with specially designed sealing plugs, which must be removed immediately prior to assembly.
A good rule is to replace the drier filter whenever the compressor is changed.
A gas contained under pressure, if allowed to escape, will undergo a sharp drop in pressure and upon expanding, it will "create cold". To give you an idea, think of how a normal spray can work: if you press on the valve for a prolonged period and let the contents escape freely, in a few seconds the can will become colder and colder, until it is icy.
In a climate control system, the expansion valve is the device which regulates coolant flow and temperature, so that it is precisely the expansion of the gas which creates the drop in temperature. To complete its journey, the coolant must pass through a valve which allows the gas to expand, with a subsequent drop in pressure and temperature.
The evaporator acts as a heat exchanger too. Conceptually, it is identical to the condenser, but it has the opposite function. Inside it, the coolant passes from a liquid to a gaseous state, absorbing heat from the environment. The air which passes through its fins is cooled and enters the passenger compartment through the air vents.
Before entering the cabin, the air passes through the passenger compartment filter.
Air conditioning is a device which is only capable of cooling, while climate control can both cool and heat the air. Air conditioning uses the characteristics of gases, which heat up or cool down when submitted to different pressures and physical stresses. There are different types available, depending on the operating mode:
Depending on the number of zones which can be individually adjusted, there is a single zone, dual zone, triple zone and four zone climate control systems available.
If a fan is switched on in a room, the moving air has the same temperature as the still air, but when it reaches you it seems cooler. On top of a mountain, where the air is zero degrees, in the sun it is easy to feel warm. Regardless of the temperature recorded by the thermometer, humidity makes us feel colder at lower temperatures and warmer at higher temperatures. The thermal comfort we perceive is not just a question of a measurement on a thermometer. The most sophisticated climate control systems operate according to equivalent temperature, or the complex management of the climate based on perceived thermal comfort, to ensure the passenger compartment occupants enjoy their required temperature. They operate using algorithms, which make the climate control system function according to various factors detected by dedicated sensors, which allow the system to anticipate and compensate for climatic changes inside and outside the passenger compartment.
One of the most common causes of functional anomalies in climate control systems is inefficient cooling circuit flow, which very slightly reduces the quantity of coolant gas, leading to a gradual reduction in performance through to a total breakdown. In these cases, careful leak detection must be performed on all of the system's components.There are various types of leak detection options: contrast solutions to be added to the coolant fluid, and UV lamps which make the contrast solution visible; electronic detectors which give off an acoustic signal when a leak is detected, however small, and including in hard to reach areas; solutions which, when sprayed in liquid form at the point where the flow is reduced, form a foam which reacts with the coolant gas. Finally, there is leak detection using nitrogen, a useful technique both when flushing the system and when checking flow, performed using special climate control flushing kits.
To ensure your climate control system always runs efficiently, you should use it often, even in winter. The climate control is a system in itself, with its own motor (the compressor), heat exchangers (condenser and evaporator), filters and tubes, and it is always under pressure, even when it is not activated.In every season, the system plays its part in improving on-board safety: by dehumidifying the air which enters the passenger compartment, it solves the problem of window misting, which can be especially irritating in autumn and winter.At the end of a long journey, especially on rainy and damp days, it is a good habit to get into to leave the air vents running on full power for a few minutes before stopping. Simply switch off the climate control system and leave only the ventilation active. This will allow the evaporator and the vents to dry and passengers can get used to the external temperature. It also limits the formation of mould and bacteria caused by damp, which can lead to unpleasant odours and allergic reactions. Regular replacement of the passenger compartment filter is crucial to ensure you always have clean air on-board.For optimum thermal comfort and to avoid thermal shocks, especially in summer, the climate control should never be programmed at too low a temperature. Ideally, the difference between the ambient temperature and the in-car temperature should be no more than 6° – 7°.Direct the cool air flow upwards and not directly on to the body. This helps the heavier cool air to mix with the lighter warm air.To ensure optimum climate control performance, it is good to recharge the coolant gas every two years.
If you notice a reduction in the performance of your climate control system and it doesn't seem to be cooling efficiently, you may need to carry out leak detection and recharge the coolant gas. In any case, it is recommended that you recharge the gas every two years.If you notice a pool of water forming underneath the front of your vehicle after travelling with the air conditioning switched on, this is not a problem: it is the evaporator dripping because the frost which forms on the panels is melting.
If your windows are often misted, even when the climate control is on, the passenger compartment air flow may be low. If the passenger compartment filter is too full of impurities or clogged for a prolonged period, it must be replaced.