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Heat Transfer - Engineering

Q1:

According to Reynolds analogy, Stanton number is equal to (where, f = Fanning friction factor)

A 2f

B f

C f/2

D f/4

ANS:C - f/2

According to Reynolds analogy, the Stanton number (St) is related to the Fanning friction factor (f) and the Nusselt number (Nu) by the expression: St=Re⋅PrNu​ Where:

  • Nu is the Nusselt number,
  • Re is the Reynolds number, and
  • Pr is the Prandtl number.
For turbulent flow in the fully developed region of a pipe, the Fanning friction factor (f) is often related to the Reynolds number (Re) by the expression: =0.0790.25f=Re0.250.079​ Now, plugging this value of �f into the Stanton number expression, we get: St=Re⋅PrNu​=Prf​ Therefore, according to the Reynolds analogy, the Stanton number is equal to: St=Prf​ So, the correct answer is: Prf​