ANS:C - forced convection

Forced convection is a mode of heat transfer that occurs when a fluid, such as air or water, is forced to flow over a surface by an external agent, such as a pump or a fan. In forced convection, the fluid movement is primarily driven by mechanical means rather than by density differences or buoyancy forces. Here's how forced convection works:

1. External Force: In forced convection, an external force, such as a fan or a pump, is used to induce fluid motion. This force overcomes the inherent resistance of the fluid to flow and creates a velocity field within the fluid.
2. Fluid Motion: As the fluid moves over the surface, it carries thermal energy with it. This fluid motion enhances heat transfer between the surface and the fluid through convection.
3. Enhanced Heat Transfer: The fluid motion increases the rate of heat transfer compared to natural convection, where fluid motion is driven by buoyancy forces. Forced convection is particularly effective in situations where natural convection alone may not provide sufficient heat transfer rates, such as in applications with low temperature differences or in situations where rapid heat removal is required.
4. Applications: Forced convection is commonly encountered in various engineering applications, including cooling systems for electronics, heat exchangers, HVAC (heating, ventilation, and air conditioning) systems, and industrial processes such as drying, curing, and chemical reactions.

In summary, forced convection is a mode of heat transfer where fluid motion is induced by external forces, leading to enhanced heat transfer rates compared to natural convection. It plays a crucial role in many engineering applications where efficient heat transfer is essential.