How many degrees, hands will be burned. Let's see, what is the skin tolerance temperature? You have to understand that first, right?
Donghua University has a paper "Heat and Moisture Transfer and Skin Burn Prediction of Fire Clothing in Fire and High Temperature Steam Environment".
Skin scald usually occurs on the skin surface, and protein in most surface tissues is easily damaged.
Mainly because: protein is afraid of heat. At high temperature, protein degenerates and loses its natural structure and activity. The temperature that the skin can bear is not high.
Henan University of Science and Technology has a paper "Modeling and Simulation Research on Temperature Field of Skin Thermal Injury", with data records.
It is generally believed that when the temperature of biological tissue is higher than the threshold of 44℃, thermal damage will occur.
There is also a paper in the journal of Applied Physiology, and there are also research records on skin temperature and skin pain during warm water immersion: people will feel pain after soaking in water at 36-40℃ for 5-6s.
This temperature is similar to soaking feet. Aren't many people not used to soaking their feet? I think it makes sense to soak your feet "wow, it's hot" or something.
Generally speaking, the temperature of human skin cannot exceed 4 or 50℃ for a long time.
How soon will the engine compartment get hot? When the car is running normally, the temperature in the engine compartment must be higher than 4 or 50℃.
When starting, its working temperature is very high. When the gasoline in the combustion chamber is ignited, the highest temperature exceeds 1000℃. Even on the surface of parts, there is a high temperature of several hundred degrees Celsius.
Hunan University's paper "Research and Improvement of Thermal Management of Automobile Engine Compartment" said that the temperature of an engine compartment of a certain vehicle was measured under different working conditions.
The results are as follows: the surface temperature of important parts in the engine compartment is between 300 ~ 67 1℃. If the skin comes into direct contact with this ingredient, it will burn instantly.
This heat will eventually spread to the whole engine compartment, making the cabin temperature higher.
This is like: the engine is like a big fireplace, installed in the room, where it is lit and baked, and the whole room is not warmed up?
Shanghai Jiaotong University has a paper "Research on Thermal Management Technology of Automobile Engine Compartment", which studies the temperature field in the engine compartment.
The results show that the temperature of running cars, cooling fans and their vicinity can reach about 90℃, far exceeding the temperature that the skin can bear.
If you reach for the lock and open the hood at this time, you are likely to get burned.
About 50 minutes after starting, the hood will heat up, but this is the temperature after the car has been running for a while and stabilized. At first, the temperature was not that high.
For example, the cold pot of cooking is cooked on the fire for a while before the pot gets hot. Doesn't mean a small fire can burn the pot to death.
There is a paper in Computer Simulation magazine, which is the modeling of the temperature field of the hood of a civil vehicle and the analysis of the universality of the model, and the data analysis of the temperature field of the test vehicle is made.
The results are as follows: around 3000s, the outer surface temperature of the engine hood tends to be stable, ranging from 39℃ to 47.8℃, and the closer to the engine center, the higher the temperature.
That is to say: about 50 minutes after the car starts, the outer surface of the hood, especially near the engine in the middle, will become hot, not to mention putting your finger into the hood to unlock it.
If you want to turn on the range hood, you'd better wait for it to cool for a while, or put on gloves and other protective measures.
The sun will be very hot.
Another situation is that the hood will get hot before the car starts, that is, the sun will be exposed.
There is a paper in the magazine "Automotive Practical Technology". When studying the influence of interior and exterior colors on the temperature inside the car after exposure, an experiment was made on the temperature of different colors of cars after exposure.
After 7 hours of exposure, the average temperature of the hood of the white car with the highest albedo can reach 45.9℃, and the highest temperature is 54.6℃.
The average temperature of black cars is 63.6℃, and the highest temperature is 8 1.8℃. Black is much hotter than white.
This temperature, if you put this hand on it, is basically similar to "stir-frying pig's trotters with a small fire".
If the car has been exposed to the sun for several hours, be careful not to touch the hood directly with your hands.
Don't touch it directly, it will cause burns. Generally speaking, if the car has been driving 1 hour, or has been exposed to the sun, the temperature of the hood may exceed the upper limit that the skin can bear, causing burns. Do not touch directly. You can wear gloves before operation.