Why plastic film greenhouse can keep warm?
Cold winter, often have a cold snap, plastic film mulching vegetable can prevent sudden frost, the leaves freeze.Concretely speaking:1. heat insulation (internal air convection is very small)2. absorb light energy (because of transparency)3. keep the water (make the vegetables fresh)
Because the heat is hard to escape through the plastic film, the temperature difference between the upper and the lower of the greenhouse can not be enlarged, and the convection is very small, so that the heat can be kept warm. The key here is the plastic film is very similar to shun donkey, sun radiation from the inside, with stubble, almost without shelter; and the heat from the inside out is the inverse stubble, resulting in heat insulation.
Solar radiation is easy to pass through plastic film, and plastic film conductivity is very bad, so that heat is difficult to spread out through plastic film, this is heat insulation.
