In turbulent pipe flow, the heat transfer coefficient h is generally proportional to Reynolds number raised to which power?

In turbulent pipe flow, the heat transfer coefficient h is generally proportional to Reynolds number raised to which power?

• A. 0.8
• B. 0.2
• C. 1.0
• D. 0.5

Answer: (A)

In turbulent pipe flow, the heat-transfer process is dominated by vigorous mixing from turbulence, which enhances convective heat transfer compared with laminar flow. Empirical correlations for fully developed turbulent convection, such as Nu ≈ 0.023 Re^0.8 Pr^n (with roughly n ≈ 0.4 for heating), show that the Nusselt number increases with Reynolds number to about the 0.8 power. Since the heat-transfer coefficient h relates to Nu by h = Nu·k/D, this leads to h ∝ Re^0.8 (assuming k and D and the Pr regime remain similar). The 0.8 exponent is an experimentally observed scaling in typical turbulent pipe flow, reflecting how stronger inertial effects at higher Re raise turbulence and mixing, but not in a one-to-one linear way.

In turbulent pipe flow, the heat-transfer process is dominated by vigorous mixing from turbulence, which enhances convective heat transfer compared with laminar flow. Empirical correlations for fully developed turbulent convection, such as Nu ≈ 0.023 Re^0.8 Pr^n (with roughly n ≈ 0.4 for heating), show that the Nusselt number increases with Reynolds number to about the 0.8 power. Since the heat-transfer coefficient h relates to Nu by h = Nu·k/D, this leads to h ∝ Re^0.8 (assuming k and D and the Pr regime remain similar). The 0.8 exponent is an experimentally observed scaling in typical turbulent pipe flow, reflecting how stronger inertial effects at higher Re raise turbulence and mixing, but not in a one-to-one linear way.