The main working area for aircraft is thousands of metres above sea level, where changes in thermal conditions require the use of appropriate temperature control systems; but also on the ground...
Heat and temperature are two concepts so closely related that colloquially they can be used as synonyms, but properly speaking, whereas heat and temperature are so closely related that colloquially they can be used as synonyms. temperature quantifies the speed or energy with which the atoms move of matter, the heat is the transfer of this energy between two materials due to the fact that they communicate with each other and are at different temperatures.
An object that is at a higher temperature than that for which it was designed will sooner or later present a problem in its operation. For example, in electronic equipment, the path of the electrons would be uncontrolled and the signals would not be transmitted as expected. On the other hand, extreme overheating can cause a material to change from a solid to a liquid, change of status known as fusion. It occurs when atoms move so much that they become detached from each other. This happens in some aircraft or components that pass through the atmosphere at an inappropriate angle or speed, usually because they have lost control of them, and inevitably results in their destruction.
As far as living beings are concerned, we also need to keep temperature levels under control so that our metabolism does not suffer. Achieving this comfort is a basic requirement for passenger aircraft.. However, occasionally there are reports of problems with a pet that may have been transported in a non-refrigerated, and therefore unsuitable, area such as the cargo hold.
As can be deduced, it is necessary to have various cooling systems to manage the heat and avoid problems resulting from overheating. A possible classification could be as follows:
Cabin refrigeration
Most aircraft fly at a considerable altitude of thousands of kilometres and are equipped with pressurised cabins to compensate for the lower level of oxygen in the air. At these altitudes the outside air is also cold, tens of degrees below zero, so it is necessary to create an indoor atmosphere with a temperature control similar to the air conditioning system we have in our homes, but with the big difference that the air does not come from a mere outdoor unit located on a terrace or balcony, but a complex air conditioning system is used. inlet air compression system from the engines.
Cooling of the structure
The structure of the aircraft usually shall not require a specific temperature protection system, as the operating range of the material is usually quite high. Only some stratospheric aircraft, such as space shuttles, will require additional thermal protection. There are various mechanisms, such as adding special plates to the fuselage, which serve to withstand the high temperatures that occur on re-entry due to friction with the atmosphere.
Equipment cooling
There are two ways of cooling equipment, blowing air with supply fans or extracting it with so-called extraction fans. In this case, the physical principle is to take advantage of thermal convection so that the air absorbs heat from the surrounding objects. The use of fans means that there is more unheated air around them.
On the other hand, it should be mentioned that water is an even better coolant than air thanks to its higher specific heat, which is the amount of energy it can absorb before increasing its temperature. This is why it is used to cool cars and also computers. In cars, the reason why it is used mixed with other additives is only to prevent freezing at temperatures below 0 °C. But using it in aircraft is a problem due to its higher weight, which is a very important parameter in this sector.
Finally, it should be noted that an additional utility of the heat management systems currently being developed and experimented with, apart from cooling, is to attempt to reuse of thermal energy by converting it into electrical energy. Fuel economy is another highly appreciated value in this industry and there is no doubt that we will see this technology implemented within a few years.
