Heat Transfer in External and Internal Flow

In external flow, the fluid is in contact with a solid surface, such as a wall or a heat exchanger. The heat transfer coefficient, h, is used to express the heat transfer from the fluid to the solid surface. This coefficient is dependent on the properties of the fluid, the velocity of the fluid, and the temperature difference between the fluid and the solid surface. Engineers use correlations and empirical data to determine the heat transfer coefficient for a given system.

Internal flow refers to the heat transfer within a fluid as it flows through a pipe or duct. The heat transfer coefficient, h, is used to express the heat transfer from the fluid to the wall of the pipe or duct. This coefficient is dependent on the properties of the fluid, the velocity of the fluid, and the temperature difference between the fluid and the wall. Engineers use correlations and empirical data to determine the heat transfer coefficient for a given system.

It's important to note that heat transfer in both external and internal flow can be enhanced by using devices such as fins, turbulators, and heat exchangers. The design of these devices requires a good understanding of heat transfer principles and the use of appropriate tools such as computational fluid dynamics (CFD) simulations.