First, expression

1, Clausius stated that heat can be spontaneously transferred from a hot object to a cold object, but it is impossible to spontaneously transfer from a cold object to a hot object.

2. Kelvin Planck pointed out that it is impossible to absorb heat from a single heat source and convert it into work without other influences.

Second, the introduction of the second law of thermodynamics

The principle of entropy increase means that the entropy of an isolated thermodynamic system does not decrease, but always increases or remains unchanged. Used to give the evolution direction of an isolated system. It shows that an isolated system cannot develop to a low entropy state, that is, it will not become orderly.

The law of entropy increase is the most scientific law, which is Einstein's view. Like matter and information, energy is one of the three basic elements of the material world. Among the laws of physics, the law of conservation of energy is the most important law, which shows that all forms of energy are always in equilibrium when they are transformed into each other.

The concept of entropy originated from physics and is used to measure the disorder degree of a thermodynamic system. The second law of thermodynamics, also known as the law of entropy increase, shows that the total chaos degree of an isolated system (that is, "entropy") will not decrease in the natural process.

Application of the second law of heat

In the field of engineering

The second law of thermodynamics can be used to design and analyze mechanical systems, heat exchangers and cooling systems. It can also be used to calculate the efficiency of thermal system and the energy flow in thermal system.

In the field of physics

The second law of thermodynamics can be used to explain and predict the thermodynamic properties of substances and the interaction between substances. It can also be used to calculate the entropy and heat capacity of matter and the thermodynamic changes of matter.

In the field of chemistry

The second law of thermodynamics can be used to explain and predict the thermodynamic properties and possible results of chemical reactions. It can also be used to calculate the entropy and heat capacity of chemical reactions and the thermodynamic changes of chemical reactions.

In the field of biology

The second law of thermodynamics can be used to explain and predict the thermodynamic properties of organisms and the interaction between organisms. It can also be used to calculate the entropy and heat capacity of organisms, as well as the thermodynamic changes of organisms.