Find out what's behind the operation of our eco-evaporative air conditioners.
The centerpiece of the evaporative cooling is the honeycomb panel. A system that cools the environments thanks to a particular method of distribution of water ensuring the constant and regular wetting of the panel. The hot air, sucked by a fan, through a panel blister wet, to evaporate a small quantity of water thus creating a system of natural evaporative cooling. The exhaust air is thus refreshed, clean and purified from odors and airborne germs and you will have a cooled environment at a very low cost!
Evaporative cooling uses one of the physical properties of the air which, as known, is able to absorb, and therefore contain, a certain amount of water vapor (water) as a function of its temperature. The relationship between the actual amount of water vapor contained in a given time and the maximum value that this may contain, defines the% (percentage) of relative humidity (RH) of the air in question. Over the air is dry and more water vapor is able to absorb, while the more moist, less able it is to receive another. The absolute quantity of vapor vapor that the air can hold depends on its temperature: the more the air is warm, and is more able to assume water vapor and vice versa. This physical characteristic of the air is clearly expressed in the psychrometric chart (shown) that shows the different conditions and typical characteristics of the moist air.
Evaporative cooling allows you to add the amount of water vapor the air missing to make it saturated (or very close to saturation), ie with a humidity close to 100%. If a volume of air has a% relative humidity (% RH) low, it means that, if properly treated, it can absorb more water until you get closer to 90/95% RH The absorption of the vapor vapor from the air is possible thanks to the heat contained in the air, allowing to evaporate a certain amount of water that turns in fact water vapor. This heat 'evaporation' is taken to the same air, which then increases its% RH losing at the same time some of its heat and thus lowering its temperature. In terms of energy reduction of the air temperature does not involves a variation of the enthalpy content of the air, since the reduction of energy sensitive (air temperature) is compensated with the increase of water vapor content (hence the concept of adiabatic cooling, that is, without changing the enthalpy content of the fluid in question).
But how do we beat the heat, but especially the summer heat, which is known to be the most annoying during some summer days, Whereas, with high rates of moisture the efficiency of the system is less than?
It is useful to address this issue, a premise: normally with increasing temperature, its Relative humidity in percent
(% RH) decreases, because the air has a greater capacity to absorb the steam so, normally during the hottest hours of the day
you have the percentages of RH lower.
But some days can be especially muggy. Add to this that the evaporative cooling system increases the moisture content of indoor air and this could make you doubt the actual beneficial obtainable. For this we is very useful another diagram, shown in Fig 4 (diagram Stedman).
This diagram expresses the concept of 'perceived heat' by relating the values of temperature and relative humidity. This concept, often used by the media during the summer, it indicates that the air temperature coupled with its UR generates a perception of an average person, similar to a air temperature higher. The greater the moisture in the air, the greater will be the perceived temperature. This diagram also provides another important value to be considered: as the air temperature decreases, also decreases the influence of the humidity values on perception. In fact, if the increase from 30 to 60% of 'RH at 33 ° C causes an increase in the perceived temperature of 8 ° C (32 to 40 ° C), when the air has a temperature of around 29 ° C the same increase of the percentage of moisture leads to an increase of the perceived by only 3 ° C (28 to 31 ° C). In this context it should be considered the work of the evaporative cooler: if the unit is can provide a temperature of the air introduced into the room at least 27/28 ° C, the increase of moisture generated by the cooler will be completely negligible for the welfare of the people. We must not forget that in the cool days of spring and autumn moisture the air can be also very high, but this does not affect the well-being perceived by us thanks to the low temperature of the air
If the percentage of moisture in the air is particularly high, the system has a lower efficiency, but in these conditions, making again reference to the diagram of Figure 4, one can understand how even in these conditions also the lowering of only a few degrees of the temperature of input into local lowers the perceived temperature. In fact, with an air temperature of 33 ° C and humidity at 70%, the heat perceived is equal to a temperature of 44 ° C. Lowering of the temperature of only 2 degrees thelatest same humidity, the perceived temperature is 6 ° C lower.