What is Heat Transfer?

Heat transfer refers to the transfer of energy due to temperature differences, also known as heat transfer. According to the second law of thermodynamics, whenever there is a temperature difference, heat must be transferred from high temperature to low temperature. Therefore, heat transfer is a very common transfer phenomenon in nature and engineering technology. Whether in the energy, aerospace, chemical, power, metallurgy, machinery, construction and other industrial sectors, or in agriculture, environmental protection and other sectors, there are many issues related to heat transfer. ^[1]

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[Definition] Heat transfer is the transfer of thermal energy due to a temperature difference. ^[2]

Heat transfer is a complex phenomenon. In essence, as long as there is a temperature difference in one medium or between two mediums, heat transfer must occur. We put different types of

Intermediate medium for heat transfer. Common mediums are water, steam, oil, salt water, ethylene glycol, etc. According to the temperature of heat transfer, it can be divided into two categories: high temperature heat transfer medium and low temperature heat transfer medium.

The phenomenon of heat transfer is ubiquitous at all times, and its impact has spread to almost all modern industrial sectors, and has also penetrated into many technical sectors such as agriculture and forestry. It can be said that with the exception of very few cases, it is difficult to find that an industry, sector or industrial process has nothing to do with heat transfer. Not only traditional industrial fields, such as energy and power, metallurgy, chemicals, transportation, building materials, machinery and food, light industry, textiles, medicine, etc., need to use a lot of relevant knowledge about heat transfer, but also such as aerospace, nuclear energy, microelectronics, Many high-tech fields such as materials, biomedical engineering, environmental engineering, new energy, and agricultural engineering also depend to varying degrees on the latest results of applied heat transfer research, and emerged like phase transitions and multiphase flow heat transfer, (super) Low-temperature heat transfer, micro-scale heat transfer, biological heat transfer and many other interdisciplinary subjects. In some links, the research and development of heat transfer technology and related materials and equipment has even become a key factor in the success of the entire system ^[4] .