The Venturi effect can cool the air. Same principle that can cause carb ice on a warm day.
"twr, bug smasher 123 is experiencing icing on our vent, need to land ASAP"
If it cools the air then where does the heat go?
Yeah I'm not sure the physics on this bake out. In a venturi / carb the air speeds up at the restriction, causing a loss in pressure, causing temperature decrease. Once the air goes out the back of the venturi the conditions "return to normal" so to speak that's why ice tends to form right at the throat and throttle plate, by the constriction, not after it. Where does the heat go in a venturi? Well it gets "used up" so to speak when the air pressure decreases, so the air itself cools down (air in the cylinder gets hot when you compress it and increase the pressure, so it gives off heat energy and feels hotter.. air in the venturi gets cool when there is a pressure drop, so it takes in heat energy and feels cooler). Sort of like the whole endothermic / exothermic reactions
**In this application though, even if they have a venturi on there to cool it down, there is no free lunch, so to speak.. the air either warms back up before it exists the vent as it returns to the normal pressure after the venturi throat, or, if the constricted venturi throat exits right into the cabin you'll have cooler air exiting but there will be less of it.. (lower pressure). I am not convinced.
If it were this easy to cool air then then the whole design of air conditioners would be much cheaper and simpler.. you could just stack a series of venturis one after the other and blow icy cool air out the back (mind you, at its core concept an AC does use expansion / compression of the refrigerant to cool things down, but the fundamentals are different, you are not compressing and expanding the air, but rather using the fluid contained in the system to "remove heat energy" from the house
