Chemical Engineering in Daily Life – Question 29 – In some cities in the north during winter, plants and trees need to be covered. Is this really useful? Standard answer already exists
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This post was last edited by yjqin1 on 2015-9-24 at 19:43. In modern China, cities of all sizes – large, medium, and small – are all very beautiful (regardless of whether they have any unique features or not). Things have changed so much over these thirty years. I remember going to Cangzhou in 1988; it seemed like just a dilapidated small county town. At that time, I wondered how Xiao Xuanfeng Chai Jin could live in such a rundown place. In 1989 and 1990, I visited the provincial capitals of Jinan, Shenyang, and Dalian; on some of the main streets in these well-known cities, the street lights were not working. Look at Chinese cities these days; even small county towns are truly magnificent. I remember that a few years ago, it took a long time to drive from the east side of Taicang City to the west side. Each one has the vibe of an international metropolis. Take landscaping for example – plants like Chinese plum, roses, crape myrtles, and hibiscus can be found everywhere. This spring in Heze, a prominent professor pointed at the pink peach blossoms all over the streets and said, “Look how beautiful these peony flowers are.” I say you’re wasting your time as Heze’s son-in-law. I saw some bonsais made from southern tree species used as roadblocks in the streets of northern cities (? What should it be called? ) done. I wonder how expensive that must be; having to move around every year is both time-consuming and costly. However, you will see that those bonsais are planted directly in the soil. In winter, gardeners simply cover them with insulating materials, and when spring comes the following year, they remove those protective covers, allowing the plants to bloom and grow leaves as usual. Over the years, I’ve been living a good life. This is no miracle; there is a chemical principle behind it. However, if the temperature during the day is zero degrees and drops to minus ten degrees in the latter half of the night, with that plant’s minimum tolerance being minus five degrees, it still does not die from the cold. However, given the thermal conductivity of its protective layer and its thickness, the temperature inside must be below minus five degrees in the latter part of the night. Why didn’t the plants die from the freeze? There must be other secrets behind this What is this mystery?
Because the temperature is high during the day, it absorbs heat and stores it, releasing it gradually at night. Greenhouse cultivation makes use of this characteristic.
The protective layer is the thermal resistance. In terms of heat transfer rate, it reduces the heat transfer rate from the plant itself to the environment. Thus, the temperature of the plants is maintained and does not drop to the ambient temperature.
This mystery still needs to be slowly explained by the teacher...
Standard answer: Second-floor view: During the day, the high temperatures cause heat to be absorbed and stored, and at night this heat is released gradually. Greenhouse cultivation makes use of this characteristic. View from Floor 3: The protective layer is the thermal resistance. In terms of heat transfer rate, it reduces the heat transfer rate from the plant itself to the environment. Thus, the temperature of the plants is maintained and does not drop to the ambient temperature. All of this is correct, but if it stays overcast with heavy snowfall and the temperature drops for several days in a row. It’s cold both during the day and at night; wouldn’t the temperature inside and outside the protective layer be similar then? From the perspective of chemical engineering principles or the principles of process transfer, or as common sense, can this be understood? Importantly, a portion of the energy in woody plants is stored in the roots in the form of starch or sugar. When the weather is cold, this sugar is transported back from the roots to the stems and dry parts under the action of capillaries, where it oxidizes slowly, thereby releasing heat and keeping the plant’s temperature slightly higher than that of the surrounding air. In the native habitats of these plants, this is sufficient, but in the colder northern regions, a temperature higher than that of the surrounding air is required. At this point, the insulation effect of the straw-based protective layer becomes very important.
Thanks for sharing, I’ve learned something! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !