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

Contents

Interface Function Documentation Page Comments

Interface

#include <codecogs/engineering/heat_transfer/convection/nusselt_flat.h>

using namespace Engineering::Heat_Transfer::Convection;

	double	Nusselt_flat (double Pr, double Re)[inline] Returns the Nusselt number for a fluid going over a flat surface.
	Real	cc_convectionNusselt_flat (Real Pr, Real Re) This function is available as a Microsoft Excel add-in.

Function Documentation

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)