Home
Back
Formula Used:
| From: | To: |
The Nusselt number represents the ratio of convective to conductive heat transfer at a boundary in a fluid. For a horizontal plate with upper surface cooled or lower surface heated, the specific correlation Nu = 0.27*(G*Pr)^0.25 is used to estimate this dimensionless number in natural convection scenarios.
The calculator uses the formula:
Where:
Explanation: This correlation specifically applies to natural convection heat transfer for horizontal plates where the upper surface is cooled or the lower surface is heated, accounting for the combined effects of buoyancy and fluid properties.
Details: Accurate Nusselt number calculation is crucial for predicting heat transfer rates in natural convection systems, designing thermal management systems, and optimizing energy efficiency in various engineering applications involving horizontal surfaces.
Tips: Enter the Grashof number and Prandtl number as positive dimensionless values. Both values must be greater than zero for accurate calculation.
Q1: When is this specific correlation applicable?
A: This correlation is specifically for natural convection over horizontal plates where the upper surface is cooled or the lower surface is heated, typically for Rayleigh numbers between 10^4 and 10^7.
Q2: What are typical values for Grashof and Prandtl numbers?
A: Grashof numbers can range from 10^4 to 10^9 for natural convection, while Prandtl numbers vary by fluid (0.7 for air, 7 for water, up to 1000 for oils).
Q3: How does surface orientation affect the Nusselt number?
A: Surface orientation significantly affects natural convection patterns. This specific correlation is optimized for horizontal plates with the described thermal conditions.
Q4: Are there limitations to this correlation?
A: This correlation is valid for laminar flow conditions and specific Rayleigh number ranges. It may not be accurate for turbulent flow or extreme temperature differences.
Q5: Can this be used for both heating and cooling scenarios?
A: Yes, this correlation applies to both cases where the upper surface is cooled or the lower surface is heated, as the buoyancy-driven flow patterns are similar in these configurations.