Forced convection is primarily characterised by:

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RRB JE CBT 2 (Mechanical Engineering) ReExam Official Paper (Held On: 04 Jun, 2025)

Answer 1

Explanation:

Forced Convection

Forced convection is a mechanism of heat transfer in which a fluid (such as air, water, or any other liquid or gas) is forced to flow over a surface or through a channel by an external device, such as a fan, pump, or blower. The external device generates motion in the fluid, facilitating the transfer of heat between the surface and the fluid. Forced convection is widely employed in various industrial and engineering applications due to its efficiency in transferring heat over large surfaces or volumes.
In forced convection, the rate of heat transfer is significantly higher compared to natural convection. This is because the external force increases the velocity of the fluid, reducing the thermal boundary layer thickness and enhancing the heat transfer coefficient.
In forced convection, an external device (such as a fan, pump, or blower) is used to induce motion in the fluid, enhancing the heat transfer process. The external force overcomes the resistance of the fluid, ensuring a controlled and efficient heat transfer mechanism. This distinguishes forced convection from natural convection, where the fluid motion is driven by natural buoyancy forces. The heat transfer in forced convection follows Newton's law of cooling, which states:

Q = h × A × ΔT

Where:

Examples of Forced Convection:

Air Conditioning Systems: Fans are used to circulate air, improving the transfer of heat between the air and the cooling/heating coils.
Car Radiators: A pump circulates coolant through the engine and radiator, while a fan helps dissipate heat from the radiator to the surrounding air.
Heat Exchangers: Pumps and blowers are employed to move fluids through the heat exchanger, enhancing the transfer of heat between the fluids.
Electronics Cooling: Fans are used to cool electronic components by forcing air over heat sinks or circuit boards.