If heat transfer is dominated by forced convection, increasing the fluid velocity will cause the heat transfer coefficient to:

If heat transfer is dominated by forced convection, increasing the fluid velocity will cause the heat transfer coefficient to:

• A. Increase
• B. Decrease
• C. Remain unchanged
• D. Depend on the medium only

Answer: (A)

In forced convection, the heat transfer coefficient h reflects how effectively the moving fluid can carry heat away from or to a surface. When you raise the fluid velocity, the thermal boundary layer near the surface becomes thinner and fresh fluid continually replaces the fluid at the surface. This enhances the temperature gradient at the surface and increases the rate of heat transfer per unit area. In practice, h is related to the Nusselt number, Nu, by h = Nu·k/L. For forced convection, Nu typically increases with the Reynolds number, Re = ρVL/μ, which means higher velocity leads to a higher Nu, and thus a higher h. So, as velocity increases, the heat transfer coefficient increases, making convection more effective at transferring heat. This aligns with the idea that when heat transfer is dominated by forced convection, faster flow improves the convective heat transfer performance, rather than decreasing it or leaving it unchanged.

In forced convection, the heat transfer coefficient h reflects how effectively the moving fluid can carry heat away from or to a surface. When you raise the fluid velocity, the thermal boundary layer near the surface becomes thinner and fresh fluid continually replaces the fluid at the surface. This enhances the temperature gradient at the surface and increases the rate of heat transfer per unit area.

In practice, h is related to the Nusselt number, Nu, by h = Nu·k/L. For forced convection, Nu typically increases with the Reynolds number, Re = ρVL/μ, which means higher velocity leads to a higher Nu, and thus a higher h. So, as velocity increases, the heat transfer coefficient increases, making convection more effective at transferring heat.

This aligns with the idea that when heat transfer is dominated by forced convection, faster flow improves the convective heat transfer performance, rather than decreasing it or leaving it unchanged.