Deron is the warmest garment material at present？ The winter moon has arrived, and these rumors should be ＂cool＂

　　[rumor]

　　◎ Our reporter Chen Xi

　　These days, there has been a cold wave weather in China, and the temperature in most areas has plummeted. The cold wave not only affected a wide range, but also was accompanied by rain and snow.

　　Some rumors related to winter have also taken advantage of this cold wave to brush a wave of "existence": "triple" La Nina brings three times the cold, velvet is the warmest clothing material at present, the longer the car is hot in winter, the better, and the frost on persimmon is a preservative … … These rumors mislead the masses and have a negative social impact.

　　Today, the reporter of Science and Technology Daily took stock of the rumors in November one by one and smashed them with the power of science.

　　"Triple" La Nina brings triple cold?

　　Truth: La Nina is just one of the factors that affect winter temperature.

　　According to the latest data released by the World Meteorological Organization, the La Ni? a event that has lasted for a long time (hereinafter referred to as La Ni? a) is likely to continue until the end of this year or longer, which will be the first time in the 21st century that there will be a "triple" La Ni? a, that is, there will be three consecutive La Ni? a winters in the northern hemisphere.

　　As soon as the news came out, it immediately attracted widespread attention, and some netizens gave their own "interpretation": "triple" La Nina will definitely bring three times the cold.

　　In this regard, Zhou Bing, chief expert of climate service of National Climate Center, said that "triple" La Nina is not triple La Nina. "Triple" La Nina means that three consecutive winters from 2020 have been affected by La Nina. The impact is not constantly superimposed year after year, nor does it mean that the climate impact will double year by year.

　　La Nina refers to the phenomenon that the sea surface temperature in the eastern and central equatorial Pacific Ocean continues to be abnormally cold, also known as the anti-El Ni? o phenomenon. When La Nina appears, it is usually accompanied by global climate chaos. At this time, China is prone to cold winter and hot summer, and the number of tropical cyclones landing in China will be more than normal, resulting in the phenomenon of "drought in the south and waterlogging in the north". In Indonesia, eastern Australia, northeastern Brazil and other places, there will be more rainfall; The equatorial regions of Africa and the southeastern United States are prone to drought.

　　In the winter when most La Nina reaches its peak, the cold air that affects our country will appear more frequently. According to statistics, from 1990s to February 2022, in autumn and winter when La Nina appeared, cold air affected China 141 times, of which 27 times reached the level of cold wave.

　　"However, there are many factors that determine the temperature in winter, and La Nina is just one of many factors." Zhou Bing emphasized that the winter temperature in China is not only closely related to the intensity of winter monsoon in East Asia, but also related to factors such as Arctic sea ice, Eurasian snow and atmospheric circulation system. Therefore, although there is a greater probability of cold temperature in La Nina’s winter, it does not mean that there will be cold winter.

　　After 1986, the frequency of "meeting" between La Nina and warm winters increased, among which 1998 and 2020 were strong warm winters. The National Climate Center pointed out in the Forecast of Climate Trends in Winter 2022/2023 and Spring 2023 released on November 3, 2022 that it is expected that the cold air intensity affecting China will be weak in general this winter (December 2022 to February 2023), and the temperature in most parts of the country will be close to the same period of the year or high.

　　Experts from the National Climate Center said that climate prediction is a highly professional scientific research business, which needs to be based on a large number of climate observation data and supported by high-resolution numerical forecasting products, so as to conduct comprehensive judgment and analysis, and finally draw scientific conclusions cautiously.

　　Deron is the warmest garment material at present?

　　Truth: There are many materials similar to its warm-keeping effect.

　　As soon as the weather turns cold, many people begin to buy thermal underwear. Go to the e-commerce platform to search for "thermal underwear", and many products have the words "Derong" on their packages. Derong has almost become the most frequent thermal clothing material this year. Many related businesses claim that Deron can generate heat by itself, and it is the warmest garment material at present.

　　So, what is the truth?

　　"Deron is a transliteration of the English word Dralon, which is an acrylic fiber developed by an international life science group in Germany. The main component is polyacrylonitrile fiber." Xu Lei, an associate professor of tianjin polytechnic university Textile Science and Engineering College, said in an interview with Science and Technology Daily that Deron is not a new thing, and it entered the Chinese market as early as 2011.

　　"Derong’s principle of keeping warm has nothing to do with self-heating, but is mainly related to the thermal conductivity of air." Xu Lei said that the thermal conductivity of an object represents its ability to transfer heat, and the low thermal conductivity of air means that its ability to transfer heat is low, that is, heat is not easily lost, so the more air the fabric can store, the better its warmth retention effect. Deron’s cross-section is double-T-shaped, which not only makes the fabric fluffy and thick, but also enables it to "lock" more still air, thus forming an insulation layer and reducing the heat dissipation of human body.

　　"However, ‘ Deron is the warmest garment material at present ’ The statement is incorrect. " Xu Lei said that although the thermal conductivity of Deron is only 0.05 W/m Kelvin, which is relatively low among thermal insulation materials, there are many materials with similar thermal insulation effects among fiber materials.

　　In addition, the moisture absorption performance of cashmere is also relatively general. In contrast, cashmere material is also very warm, and it is soft, comfortable, hygroscopic and elastic. Another example is the down jacket, whose high bulkiness can also retain a large amount of static air, thus playing a warm role and not easily generating static electricity.

　　Is the frost on persimmon a preservative?

　　Truth: Frost is a natural persimmon frost.

　　Persimmon is a cake-like food made of persimmon, and it is also one of the most anticipated foods in winter. Everyone who has eaten persimmon knows that there is more or less a layer of white powder on persimmon, but most people don’t know what this layer of frost is, so it is circulated on the Internet that it is an artificially added preservative.

　　In this regard, Tian Shufen, a professor from tianjin agricultural university, said in an interview with the Science and Technology Daily that the white frost on persimmon is called persimmon frost, which is a naturally formed icing in the production process of persimmon, and is not a preservative, which is harmless to the human body, and consumers can safely eat it.

　　When making persimmon, you need to peel the persimmon first, and then dry the peeled persimmon. In the process of drying in the sun, persimmon will separate out nutrients such as fructose and glucose. After the water evaporates, these nutrients will gradually accumulate and crystallize, and finally persimmon cream will be formed.

　　"Persimmon cream has the effects of moistening lung, relieving cough, stopping bleeding, promoting fluid production and relieving sore throat, and has certain curative effect on symptoms such as sore throat and cough." Tian Shufen introduced that persimmon cream is rich in vitamin B_2, which also has a certain therapeutic effect on aphtha.

　　Generally speaking, the amount of persimmon cream on the outer layer of persimmon is determined by the temperature and drying time. The colder the weather and the longer the drying time, the sweeter the persimmon will be and the more persimmon cream will be. In the process of storage and transportation, if the ambient temperature rises, persimmon frost may melt and become less, which is what we often call "returning frost".

　　However, consumers don’t need to excessively pursue the amount of persimmon cream. They need to be wary of unscrupulous merchants who artificially sprinkle flour, starch and other substances on persimmon in order to improve the "face value" of persimmon. After artificial "whitening", the persimmon looks even, but as long as it is shaken gently, the white powder on it will fall off, and its taste is not the sweet feeling of persimmon cream.

　　The longer the car is hot in winter, the better?

　　Truth: Overheating a car can damage the engine.

　　Before exercise, people usually warm up in advance in order to reduce the harm caused by exercise. Before a car runs, it also needs a "hot car". Experienced old drivers know that in winter, after the car is started in outdoor low temperature environment, it needs to run at idle speed (make the car engine run in neutral position) for a period of time before driving normally.

　　Recently, however, many people said that the longer the warm-up time is, the better, because it is too cold outdoors in winter, which can make the engine warm up more fully.

　　Does this statement make sense?

　　In this regard, Liu Jun, a teacher from the School of Automotive Engineering of Tianjin Vocational College, said in an interview with the Science and Technology Daily reporter that in winter, due to the low outdoor temperature and poor fuel atomization, it is best to gradually heat up the engine when starting it outdoors, and it is not appropriate to use the engine with accelerated and afterburner, so as to reduce the wear of the engine and improve fuel economy.

　　In addition, under the condition of low temperature, the fluidity of engine oil will decrease and the viscosity will increase, so it is difficult to lubricate the engine quickly. Therefore, it is necessary to warm up the car before driving in winter, but the damage to the car caused by excessive warm-up is not small.

　　"There are two main aspects of the damage to the car when the hot car is too long. First, it will make the engine produce carbon deposit (a burnt substance produced by unsaturated olefin and gum in fuel at high temperature during engine operation), which will further affect its performance, especially shorten the service life of engine spark plugs. Second, in the process of idling, the fuel concentration is high, and idling for a long time will waste fuel, increase pollutant emissions, and increase the workload of three-way catalytic converters and particle traps (OPF). " Liu Jun explained.

　　For pure electric vehicles, Liu Jun reminded that the driving device of electric vehicles is mainly composed of motors, power batteries and control systems, and the energy for driving pure electric vehicles comes from batteries, so there is no hot car problem. However, it should be noted that the hybrid vehicle needs to be warmed up. When its mileage exceeds the cruising range in pure electric mode, it needs to be switched from pure electric mode to fuel mode. At this time, if it is not warmed up, it will also damage the engine. Therefore, in this case, the driver had better warm up the car in fuel mode before driving normally.