The Prandtl Number ($Pr$) is a dimensionless parameter used in fluid mechanics to characterize the ratio of momentum diffusivity to thermal diffusivity in a fluid. It provides information about the relative rates of momentum and heat transfer within the fluid. The Prandtl Number is defined as the ratio of momentum diffusivity (kinematic viscosity) to thermal diffusivity of the fluid. The Prandtl Number is dimensionless.The formula for the Prandtl Number is given by:

Where:

• $Pr$ is the Prandtl Number,
• Dynamic viscosity is the measure of the fluid’s resistance to flow, 
• Thermal conductivity is the measure of the fluid’s ability to conduct heat.