Question

Stanton diagram is a plot of -

1. Friction factor against Reynolds number
2. Friction factor against log of Reynolds number
3. Log of friction factor against Reynolds number
4. Log of friction factor against log of Reynolds number

Answer 1

Correct Answer - Option 4 : Log of friction factor against log of Reynolds number

Explanation:

• Stanton Number defines the ratio of heat transferred through the fluid to the thermal capacity of the same fluid.
• Mathematically, it is the ratio of Nusselts Number to the product of Reynolds Number and Prandtl Number.
• The Reynolds analogy can be used to give information about the scaling of various effects as well as initial estimates for heat transfer.
• It is emphasized that it is a useful tool based on a hypothesis about the mechanism of heat transfer and shear stress and not a physical law.

\(St=\frac{Nu}{Re\times Pr}\)

For Prandtl number = 1

\(St=\frac{C_f}{2}\)

where C_f is the skin friction coefficient.

For other cases, it is called Reynolds Colburn Analogy. According to this,

\(St\times Pr^{2/3}=\frac{C_f}{2}\)

Stanton Diagram is the plot of the airflow friction coefficient against the Reynolds number. It is a plot of Log of friction factor against the log of Reynolds number more accurately.