engineeringheat_transferconvection

Nusselt extpipe

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#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.
Click for details on using CodeCogs in ExcelReal cc_convectionNusselt_extpipe (Real Pr, Real Prw, Real Re)
This function is available as a Microsoft Excel add-in.

Function Documentation

Nusselt Extpipe Calculator

  

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doubleNusselt_extpipedoublePr
doublePrw
doubleRe )[inline]
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

(1)
\displaystyle {\rm Nu} = 0.5 {\rm Re}^{0.5} {\rm Pr}^{0.38}
\left(\frac{\rm Pr}{\rm Pr_w}\right)\right)^{0.25} \qquad
\mbox{(laminar case)}

and

(2)
\displaystyle {\rm Nu} = 0.25 {\rm Re}^{0.6} {\rm Pr}^{0.38}
\left(\frac{\rm Pr}{\rm Pr_w}\right)\right)^{0.25} \qquad
\mbox{(turbulent case)}

where {\rm Re} is the Reynolds number, {\rm Pr} is the Prandtl number of the fluid and {\rm Pr_w} 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.

1/extpipe-378.png
Example:
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
Parameters:
Prthe Prandtl number of the fluid
Prwthe Prandtl number of the fluid at the temperature of the wall
Rethe Reynolds number of the fluid
Returns:
the Nusselt number of the fluid with given parameters
References:
Dan Stefanescu, Mircea Marinescu - "Termotehnica"
Authors:
Grigore Bentea, Lucian Bentea (November 2006)
Source Code:
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Last Modified: 18 Oct 07 @ 17:07     Page Rendered: 2008-05-08 06:48:17

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