TERMODINAMICS

On the day of the test, we had 40ºC of temperature (in the shade) and 10% of Relative Humidity. We place these values ​​in the Chart.

II prototype : Sancho Panza. Madrid, 17 June 2022

Taking this point to the ordinate axis, we’ll have the amount of water in grams per Kilogram of dry air: 5 grams.

And if we draw a parallel through this point, we can obtain the volume that our air occupies compared to what the same air would occupy, but totally dry. This makes 0.895 m^3/Kg

Now is when we inject the water. It quickly goes into a vapor state. We add as much as we need to get the air saturated.

This thermodinamic analysis corresponds to the test we performed in Madrid, the 17 of June 2022.

To analyze what happens at the top of the tower, we will use the psychrometric chart.

What temperature will be the air now?

Well, going down the vertical axis we will find out :

19 ºC !!!

It has dropped 21ºC in a few seconds!

What happened to the specific volume of air?

As you can see below 1 Kg of the new mixture of air occupies 0.845 m3/Kg

This means that compared with the ambient air it occupies

0.895 – 0.845 = 0.05 m3/Kg

50 litres less per every Kg !!

We can look at this in term of density , since the density is the inverse of the specific volume,(densities Kg/m3):

1/0.895 – 1/0.845 = 1.1173 – 1.1834 = 0.066 Kg /m3

That is, every cubic metre of air inside our pipe weighs 66 grams more

than another cubic metre in the surrounding air and therefore it falls.

Below you can see similar hypothetical results obtained starting from different initial ambient conditions (variations of the ambient conditions (T and HR ).