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# Nusselt flat

Returns the Nusselt number for a fluid going over a flat surface.
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## Nusselt Flat

 doubleNusselt_flat( double Pr double Re )[inline]
This module calculates the Nusselt number for a fluid which flows over a flat surface, the flow being either laminar or turbulent. The fluid must keep its state of matter during the heat transfer process.

The formulae for each case are given by

and

where is the Reynolds number and is the Prandtl number of the fluid. If the Reynolds number is less than 2000 the flow is considered laminar, while if it is greater than 4000 the flow is considered turbulent.

In the diagram below the relation between the velocity of the fluid and its corresponding Reynolds number is shown, as well as the unit heat flow in the laminar, unpredictable and turbulent cases.

### Example 1

The following code calculates the Nusselt number for Ethylene Glycol at 17 degrees Celsius, considering both the laminar and turbulent cases.
#include <codecogs/engineering/heat_transfer/convection/nusselt_flat.h>
#include <stdio.h>

int main()
{
double Pr = 233.7745380139, Re1 = 1700, Re2 = 4200;

printf("\nEthylene Glycol at 17 deg. Celsius\n\n");

printf("Re = %.2lf (laminar flow)\n", Re1);
printf("Nu = %.4lf\n\n",
Engineering::Heat_Transfer::Convection::Nusselt_flat(Pr, Re1));

printf("Re = %.2lf (turbulent flow)\n", Re2);
printf("Nu = %.4lf\n\n",
Engineering::Heat_Transfer::Convection::Nusselt_flat(Pr, Re2));

return 0;
}
Output
Ethylene Glycol at 17 deg. Celsius

Re = 1700.00 (laminar flow)
Nu = 211.1873

Re = 4200.00 (turbulent flow)
Nu = 17041.1869

### References

Dan Stefanescu, Mircea Marinescu - "Termotehnica"

### Parameters

 Pr the Prandtl number of the fluid Re the Reynolds number of the fluid

### Returns

the Nusselt number of the fluid with given parameters

### Authors

Grigore Bentea, Lucian Bentea (November 2006)
##### Source Code

Source code is available when you buy a Commercial licence.

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