What Is Convective Heat Transfer?

Convective heat transfer is a phenomenon of heat transfer that occurs during fluid flow. ^[1] Mainly due to the movement of the particle position, the temperature tends to be uniform. Although the main mode of heat transfer in liquids and gases is convective heat transfer, it is often accompanied by heat conduction. Usually due to different reasons, there are two types of natural convection and forced convection. According to the flow state, it can be divided into laminar heat transfer and turbulent heat transfer. Convective heat transfer often encountered in the chemical industry is the transfer of heat from a fluid to a solid wall surface (such as the wall of a container or a duct near the side of the hot fluid), or from the solid wall to the surrounding fluid (such as near a cold fluid). Side of the duct wall, etc.). This process of transferring fluid from the wall to the fluid or vice versa is often referred to as heat supply.

Convection only occurs in fluids, and it refers to the heat transfer caused by the relative displacement between various parts of the fluid due to the macroscopic motion of the fluid.

When the fluid flows turbulently along the wall, a stagnant inner layer always exists near the wall. There is a transition layer between the stagnant inner layer and the turbulent body. right

Convective heat transfer refers to the heat transfer of fluid particles at different temperatures in motion. Due to the different causes of fluid movement, convection is divided into natural convection

The heat transfer process is an important research topic in the field of engineering thermophysics and chemical engineering. Strengthening the heat transfer process is one of the main research directions. The traditional method of enhanced heat transfer is to strengthen the forced convective heat transfer of the fluid in the tube by means of artificial rough walls, mechanical stirring, vibration, and fluid rotation. The use of mutual coupling between different physical fields to achieve enhanced heat transfer is a new enhanced heat transfer technology developed in recent years, which has the advantages of high efficiency and wide application. The use of external fields to enhance the transfer process is the current research hotspot. Among them, the use of electric fields to enhance heat transfer is an important technical method. The current research and applications are mainly focused on electric fields to enhance boiling and nucleation. ^[4]

The physical meaning of the system's enthalpy under the action of the electric field is: when the electric field is constant, the increase of the system's enthalpy equals the heat absorbed by the system from the outside, or the decrease of the enthalpy equals the heat emitted by the system. The thermodynamic mechanism of the electric field enhanced convective heat transfer process can be explained by the change of the system's enthalpy and temperature with the applied electric field. In the isothermal process, the system's enthalpy decreases with the increase of the electric field. During the adiabatic process, the system temperature increases with the electric field increase. If there is an electric field at the heat exchange site of the system, this electric field will effectively strengthen the heat transfer process by changing both the temperature of the system and the enthalpy of the system. ^[4]