Forced convection is a type of heat transfer that occurs when a fluid, such as air or water, is forced to move over a surface by an external source such as a fan or pump. This results in a higher rate of heat transfer compared to natural convection, where the fluid movement is caused by density differences due to temperature variations.
Forced convection requires an external force, such as a fan or pump, to move the fluid while natural convection relies on density differences due to temperature variations. This means that forced convection can be controlled and manipulated more easily, whereas natural convection is dependent on the surrounding conditions.
The rate of heat transfer in forced convection is influenced by several factors, including the velocity of the fluid, the temperature difference between the fluid and the surface, the properties of the fluid, and the geometry and surface characteristics of the surface. Additionally, the type of flow (laminar or turbulent) and the presence of obstacles in the flow path can also affect the heat transfer rate.
The heat transfer rate in forced convection can be calculated using the following equation: Q = hA(Ts - Tf), where Q is the heat transfer rate, h is the convective heat transfer coefficient, A is the surface area, Ts is the surface temperature, and Tf is the fluid temperature. The convective heat transfer coefficient is dependent on the fluid properties, flow velocity, and surface characteristics.
Forced convection is commonly used in various industries for cooling or heating purposes, such as in HVAC systems, refrigeration units, and heat exchangers. It is also utilized in processes that require precise temperature control, such as in chemical and food processing industries. Additionally, forced convection is important in the design of aircraft and automobiles for efficient cooling of engines and other components.