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Prandtl Number Formula:
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The Prandtl Number or Prandtl group is a dimensionless number, named after the German physicist Ludwig Prandtl, defined as the ratio of momentum diffusivity to thermal diffusivity. It characterizes the relative thickness of the momentum and thermal boundary layers.
The calculator uses the Prandtl Number formula:
Where:
Explanation: The Prandtl Number is calculated as the ratio of Peclet Number to Reynolds Number, representing the relationship between momentum and thermal diffusivities.
Details: The Prandtl Number is crucial in heat transfer and fluid mechanics calculations. It helps determine the relative effectiveness of momentum and thermal transport in fluid flow, which is essential in designing heat exchangers, cooling systems, and various thermal engineering applications.
Tips: Enter Peclet Number and Reynolds Number as positive dimensionless values. Both values must be greater than zero for accurate calculation.
Q1: What does a high Prandtl Number indicate?
A: A high Prandtl Number indicates that the momentum diffusivity dominates over thermal diffusivity, meaning momentum spreads more rapidly than heat in the fluid.
Q2: What does a low Prandtl Number indicate?
A: A low Prandtl Number indicates that thermal diffusivity dominates over momentum diffusivity, meaning heat spreads more rapidly than momentum in the fluid.
Q3: What are typical Prandtl Number values for common fluids?
A: For gases, Pr ≈ 0.7-1.0; for water, Pr ≈ 7; for oils, Pr ≈ 100-1000; for liquid metals, Pr ≈ 0.01-0.1.
Q4: How is Prandtl Number related to boundary layer thickness?
A: The Prandtl Number determines the relative thickness of the momentum and thermal boundary layers. For Pr > 1, the momentum boundary layer is thicker than the thermal boundary layer.
Q5: Can Prandtl Number be less than 1?
A: Yes, for fluids where thermal diffusivity is greater than momentum diffusivity, such as liquid metals, the Prandtl Number can be less than 1.