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

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Interface

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

using namespace Engineering::Thermodynamics::Convection;

inline double Nusselt_flat(double Pr, double Re)

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

${\rm Nu} = 0.335 {\rm Re}^{0.5} {\rm Pr}^{0.5} \qquad \mbox{(laminar case)}$

(1)

and

${\rm Nu} = 0.36 {\rm Re}^{0.8} {\rm Pr}^{0.75} \qquad \mbox{(turbulent case)}$

(2)

where ${\rm Re}$ is the Reynolds number and ${\rm Pr}$ 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.

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

Parameters

the Prandtl number of the fluid

the Reynolds number of the fluid

Returns

the Nusselt number of the fluid with given parameters

References

Dan Stefanescu, Mircea Marinescu - "Termotehnica"

Interactive Calculator

Result –