NEW PHYSICAL QUANTITIES IN HEAT

Some new concepts, such as potential, potential energy, velocity, kinetic energy of heat, are introduced into heat based on analogy with mechanics and electrics. As a result conservation equations for motion of heat can be established. In the irreversible process of heat transfer, what dissipated is the "energy" of heat. Taking the least dissipation of the energy of heat (thermal resistance) as an objective function, heat transfer can be optimized. Fourier's law is the simplified momentum equation of heat when the variation of momentum can be ignored, and it breaks down under extreme conditions (i.e. ultra low temperature, supertransient, nanoscale). Introducing such new quantities can also explain the abnormal phenomena, e.g., thermal wave and size effect of thermal conductivity.