Heat exchange systems typically exchange heat through both conduction and convection. Thermal conduction is a common form of heat transfer in which there is no relative displacement between different parts of the fluid during the process; Heat exchanger convection is the process of heat transfer caused by relative displacement of particles in different parts of a fluid. Heat exchanger convection can be divided into forced convection and natural convection. Forced convection uses mechanical energy (such as stirring) to induce fluid convection and transfer heat.