Nusselt Number and heat transfer coefficient Calculator

Nusselt Number – Definition

The Nusselt number (Nu) is a dimensionless parameter that measures the enhancement of heat transfer through a fluid layer as a result of convection relative to conduction alone. A higher Nusselt number indicates stronger convective heat transfer.

Heat Transfer Coefficient – Definition

The convective heat transfer coefficient (h) quantifies how effectively a fluid transfers heat at a solid boundary. It depends on fluid motion, thermal properties, and flow conditions.

Background Theory

For turbulent forced convection inside smooth tubes, the Dittus–Boelter correlation is widely used:

Where:

• Re = Reynolds number

• Pr = Prandtl number

• n = 0.4 for heating the fluid

• n = 0.3 for cooling the fluid

Once the Nusselt number is known, the heat transfer coefficient can be calculated using:

Where:

• k = fluid thermal conductivity (W/m·K)

• D = pipe diameter (m)

These relationships are essential for designing heat exchangers, determining cooling/heating performance, and analyzing convective processes.

How This Calculator Works

This calculator estimates both the Nusselt number and the convective heat transfer coefficient by:

1. Accepting user inputs for Re, Pr, thermal conductivity (k), and pipe diameter (D)

2. Allowing you to choose whether the fluid is being heated or cooled

3. Applying the Dittus–Boelter correlation to compute the Nusselt number

4. Using the relation h=Nu⋅k/D to compute the heat transfer coefficient

5. Displaying both results instantly

This provides a fast and reliable way to analyze internal con