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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 in fluid flow.
The calculator uses the Prandtl Number formula:
Where:
Explanation: The Prandtl number represents the ratio of momentum diffusivity to thermal diffusivity, indicating how quickly momentum diffuses compared to heat in a fluid.
Details: The Prandtl number is crucial in convective heat transfer calculations as it helps determine the relative growth of velocity and thermal boundary layers. It's essential for predicting heat transfer rates in various engineering applications.
Tips: Enter molecular diffusivity of momentum and molecular diffusivity of heat in m²/s. Both values must be positive numbers greater than zero.
Q1: What does a high Prandtl number indicate?
A: A high Prandtl number (Pr >> 1) indicates that momentum diffuses more rapidly than heat, meaning thermal boundary layers are thinner than velocity boundary layers.
Q2: What does a low Prandtl number indicate?
A: A low Prandtl number (Pr << 1) indicates that heat diffuses more rapidly than momentum, meaning thermal boundary layers are thicker than velocity boundary layers.
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 does Prandtl number affect heat transfer?
A: Prandtl number influences the relationship between fluid flow and heat transfer, affecting the Nusselt number and overall heat transfer coefficients.
Q5: Is Prandtl number temperature-dependent?
A: Yes, Prandtl number varies with temperature as both momentum and thermal diffusivities are temperature-dependent properties of fluids.