By: Lia Contesso
Submitted: 2010-08-04 05:19:38 | Word Count: 542
Nowadays the principle of the transmission of the heat is used in a more sophisticated way from the scientific and technological point of view in the heat exchanger and in the cooling towers, that are always in function thanks to the due maintenance, taking advantage of the evaporative mass transferral, so that water gives part of its energy to the air, thus lowering its temperature.
Calidariums and tepidariums of the Roman thermal baths used the principle of the heat exchange in the suspensura, which were pilasters on which the floor was based on; the floor was heated by the hot air that circulated thanks to the space created by the suspensura and that was produced by an oven, the praefurnium.
Hence, the suspensura was a, ancestor of the modern heat exchangers, from which the air exchangers come; in the case of the suspensura built in the Roman thermal baths and in some palaces, the exchangers regeneration was simply determined by the alimentation of the oven that was used to make the air necessary to generate the heating mechanism hot.
To allow the air circulating freely in the modern exchangers it is necessary to make a regular cleaning: the pipes must be free from any residual not to limit the passing of the air that, circulating, allows the exchange of heat energy. The cooling towers are heat exchangers as well: their functioning follows the principle of the heat exchange between gases and liquids, so the water that enters at a temperature will modify it after having met the gas (that can be water vapour), reaching the exit with a lower temperature. The exchange happens thanks to the use of fans, that push the ait towards the water, even though this can happen even without fans, in the bigger cooling towers, which can exploit the water evaporation thus saving energy, but the physical conformation of the towers will have to allow it: this mens that they will have to be vertical so that gases and liquids can meet following their natural directions.
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To be able to work properly, cooling towers need the air not to be saturated in water vapour: for example, they can have some difficulties in a rainy day, because the air is saturated, hence the exchange between gas and liquids is not possible. Everything goes around the state of the air, which the drier it is the more it can exchange heat with the water, thus making it lose temperature; the cooling towers are an example of the exploiting of the physics law in the products used in industry to reach the aim, just like many others in fact: just think, for example, of the heaters, that use the heat exchange from inside the pipe towards the outside. The cold water, in fact, gets hot at the base and when it reaches the temperature it goes up, just like the water boiling in a pot: it gets hot at the basis, near the fire, it goes up, it cools and goes down again, circulating again like this as long as the fire burns.
