Sunday, July 23, 2017

Frost prevention, rain enhancement, air pollution dilution

Although I do not drink wine, I like grapes, and I read that grapes had been damaged by frost in France. Here is an idea: Have a long pipe running through the vineyards, with holes in to let out water vapour. Boil water at one end of the pipe (or at points along the pipe) and water vapour will come out all along the pipe into the vineyards. This will increase the sky temperature by increasing relative humidity and the greenhouse effect and help reduce frost.
Hot water vapour actually radiates heat. The book "Fundamentals of Thermal-Fluid Sciences" by Cengel and Turner says that a 1-metre thick layer of water vapor at 1 atm pressure and at 100 deg C emits more than 50% of the energy that a blackbody would emit at the same temperature. Energy will therefore be radiated to the vines.
Regarding cold lower valleys, what usually happens is that the cold air comes down the sides of a valley and sinks below the warmer air (which could be only 10 metres above it). Helicopters are used to mix the warmer air above with the colder air to warm up the air immediately above the ground and higher. This method would also cause mixing because the vapour coming out the pipe would be less dense than the air, causing it to rise and mixing warmer air above with the colder air. One could also ensure that the vapour comes out at fairly high pressure to ensure mixing. The system could be used to enhance convectional rain or dilute pollution in cities by means of convection (dirty air rises out of the city).

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