英語(yǔ)翻譯
Heat,as a form of energy,cannot be created or destroyed.heat can be transferred from one substance to another.
Heat always tends to pass from warmer objects to cooler ones.When a warm substance comes in contact with a cold substance,giving some of its energy to the cold molecules.This is only one way to transfer heat.
In a chemical plant,for example,in a refinery,transfer of heat is very important.The successful operation of most processes is dependent on correct application of the principles of heat transfer.Where we are handling a hot material,we may insulate the system to hold the heat in;where the material is cold,we may insulate to keep the heat out.Efficient equipment,designed to take full advantage of processing heat,is in use in almost all chemical plants.
Three methods of heat transfer are conduction,convention,and radiation.Conduction is the transfer of heat that occurs by direct contact between two objects at different temperatures,or the transfer from one part of an object to another part of the same object,without movement or mixing of particles.
If a silver spoon is placed in a cup of hot coffee ,the handle of the spoon will get hot.Due to the molecular collisions,heat is transferred from the coffee to the spoon.The spoon becomes hot since it gains heat,and the coffee gets a little cooler since it loses some heat.Similarly,when one end of an iron poker is placed in a fire,the other end will get too hot to touch,if,however,one end of a wooden rod is placed in afire the other end will be warmed hardly at all.