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AT THE BASE OF THE AIR CONDITIONING: FEATURES OF THE AIR |
In order to understand the fundamental principles of the air conditioning process it is useful to examine the protagonist of this mechanism, the gas that we call air.
More properly the atmospheric air is a mixture of two gases, the dry air and the water vapor. The features of the air allow it to be considered very similar to a “perfect gas”; in reality the “perfect gas” doesn’t exist, but it constitutes a model of ideal reference that allows to describe in a simple but at the same time likely way the behavior of a gas exposed to transformations, natural or provoked by mechanical or thermodynamic processes, as it happens for example in the air conditioning system.
A perfect gas is formed by a countless amount of small particles that continuously move around in an irregular way. The particles don’t collide but, because of their movement, hit the walls of the container in which the gas is contained and they exercise a force. The collective action of all the particles (considering a gas volume of 1 mm 3, we must think about the presence of 10 million billions of particles), corresponds to the so-called pressure.
The particles of the gas can vary their speed and consequently determine a pressure variation, if subjected to heating. If the volume of the gas remains constant, a temperature rise will correspond to a pressure increase according to a direct proportionality.
Two essential factors to be considered during all the transformations related to air-conditioning are air temperature and pressure.
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