Misting Vapor into the Air

[Jeremiah Robinson]

Jack Rife just turned me onto the idea of misting warm water into your greenhouse on cold nights.  He says his experience is that it warms up the greenhouse.  

Has anyone had experience with this in cold weather (Jack is from Florida).

This seems to relate to this thread.

[Pat James]

Spraying water has long been a way to prevent citrus from freezing. The idea is that water is above freezing (32) by definition.

I've used misting to COOL my greenhouse in the same way you might have have seen the misters at amusement parks in the summer. I also strung a line over my swimming pool fish tank to mist last summer. The idea being that as evaporation happened in the air, some of the heat would dissipate. Not sure how effective that was, but I was in a crisis situation. I also put a fountain pump in the shallow end to add oxygen and dissipate some of the heat. My water felt like warm tea.

[Jeremiah Robinson]

This seems counter-intuitive.  How can mist both heat and cool?

[Max Gfx]

I'm trying to figure out how the warm water mist can carry very far before losing all of its heat. Ever seen videos of people making pet clouds in the winter with a cup of warm water? Once that water becomes an air-borne mist, I don't see how it could retain any heat for more than a second.

[Pat James]

The idea is water is at least 32 degrees. Any colder and it is ice. The idea of spraying citrus was to keep the the plants from freezing. It is not going to warm them up alot.

As far as misting to cool it is the evaporation that carries away some of the heat. It's not going to make drastic changes but often some is enough.

And yes it seems counter intuitive to be able to both heat and cool, just remember that heat/energy goes from where it is to where it isn't, seeking equilibrium. Google it for a better explanation on how it works.

[Jeremiah Robinson]

I think it kind-of makes sense.  The goal in heating would be to aim the mist at surfaces you don't want to freeze, such as plant leaves.  They do that in this area for strawberries when we get May frost.

You would be taking heat from the air by evaporating the mist, losing some of it to the greenhouse walls.  But then you would gain some of that back as the water freezes.

I think there might be problems when it's below zero outside, but it could extend warm-season crops a bit.

[Pat James]

LOL, I. Don't think the method would work so well with below 0 temps.... probably cover everything in a blanket of man-made snow/ice.