Q1: At what value of Prandtl number, conduction is negligible in the turbulent core of a fluid flowing through a heated pipe ?

ANS:C - > 0.6

In the turbulent core of a fluid flowing through a heated pipe, conduction becomes negligible when the Prandtl number (Pr) is less than 0.1. Explanation:

• The Prandtl number (Pr) is a dimensionless number that represents the ratio of momentum diffusivity (kinematic viscosity) to thermal diffusivity. It quantifies the relative importance of momentum and thermal diffusivities in a fluid.
• For most common fluids, such as water and air, with Prandtl numbers greater than 0.1, conduction is typically significant and contributes to heat transfer.
• However, in the turbulent core of a fluid flow, where convective heat transfer dominates, the fluid mixes rapidly, reducing the significance of thermal boundary layers and enhancing heat transfer rates.