Returns the Nusselt number for a fluid flowing over a pipe.

Contents

Interface Function Documentation Page Comments

Interface

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

using namespace Engineering::Heat_Transfer::Convection;

	double	Nusselt_extpipe (double Pr, double Prw, double Re)[inline] Returns the Nusselt number for a fluid flowing over a pipe.
	Real	cc_convectionNusselt_extpipe (Real Pr, Real Prw, Real Re) This function is available as a Microsoft Excel add-in.

Function Documentation

This module calculates the Nusselt number of a fluid which flows over a pipe, 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, is the Prandtl number of the fluid and is the Prandtl number of the fluid at the temperature of the pipe wall. 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 diagrams below the unit heat flow is shown in the laminar and turbulent regimes.

Example 1:

The following code calculates the Nusselt number for Water at 50 degrees Celsius flowing over a pipe at 20 degrees Celsius, considering both the laminar and turbulent cases.

#include <codecogs/engineering/heat_transfer/convection/nusselt_extpipe.h>
#include <stdio.h>
 
int main()
{
  double Pr = 0.71977, Prw = 6.5870, Re1 = 1300, Re2 = 6000;
 
  printf("\nWater at 50 deg. Celsius\n");
  printf("flowing over a pipe at 20 deg. Celsius\n\n");
 
  printf("Re = %.2lf (laminar flow)\n", Re1);
  printf("Nu = %.4lf\n\n", 
  Engineering::Heat_Transfer::Convection::Nusselt_extpipe(Pr, Prw, Re1));
 
  printf("Re = %.2lf (turbulent flow)\n", Re2);
  printf("Nu = %.4lf\n\n", 
  Engineering::Heat_Transfer::Convection::Nusselt_extpipe(Pr, Prw, Re2));
 
  return 0;
}

Output:

Water at 50 deg. Celsius
flowing over a pipe at 20 deg. Celsius
 
Re = 1300.00 (laminar flow)
Nu = 9.1475
 
Re = 6000.00 (turbulent flow)
Nu = 23.4526

References:

Dan Stefanescu, Mircea Marinescu - "Termotehnica"

Parameters:

Pr	the Prandtl number of the fluid
Prw	the Prandtl number of the fluid at the temperature of the wall
Re	the Reynolds number of the fluid

Returns:

the Nusselt number of the fluid with given parameters

Authors:

Grigore Bentea, Lucian Bentea (November 2006)