Black balloons don't reflect light, but they absorb a lot of heat. Colorless and transparent balloons reflect light to some extent, but they don't absorb as much heat as black ones. The black one may be sunburned.
In the research process of absorbing solar energy, the relationship of surface color, controlling water quality and initial temperature, and the same exposure time, absorbing solar energy through the study of temperature change, using the control variable method, under the premise of water quality, initial temperature and the same exposure time, the water temperature of black plastic bag rises faster, so the surface area of solar water heater. Black is suitable.
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Precautions for using plastic bags:
1, commonly used food plastic bags are mostly polyethylene films, which are non-toxic and can be used to hold food. There is also a membrane made of PVC, which is not toxic in itself, but the additives added according to the purpose of the membrane are often harmful to the human body and have certain toxicity. Therefore, this film and plastic bags made of this film are not suitable for holding food.
2. It is suggested that it is best not to use plastic bags to pack hot food with high oil content, such as mala Tang and hot fried dough sticks.
In addition, before packing food in plastic bags, carefully check whether there are foreign objects in the plastic bags, which feel rough or have peculiar smell. This kind of plastic bag may be made of waste plastic, which is easy to harm human health.