flow

Calculates the convective heat flow per unit area of a fluid.

Controller: CodeCogs

Contents

Interface
Flow
Page Comments

Interface

C++

Excel

Flow

doubleflow(	double	`lambda`
	double	`L`
	double	`dT`
	double	`Nu`	)

This module computes the convective heat flow per unit area of a fluid either going over a flat surface, over the exterior surface of a pipe or going through a pipe. It is recommended that one uses this module in combination with either one of the following components: Engineering/Heat_Transfer/Convection/Nusselt_flat, Engineering/Heat_Transfer/Convection/Nusselt_extpipe or Engineering/Heat_Transfer/Convection/Nusselt_intpipe.

Generally speaking the convective heat flow per unit area is given by the formula

$q = \frac{\lambda}{L}{\rm Nu} \Delta T \qquad \left[\frac{W}{m^2}\right]$

(2)

where $\inline {\rm Nu}$ is the Nusselt number of the fluid, $\inline \lambda$ is its thermal conductivity, $\inline L$ is the characteristic length and $\inline \Delta T$ is the temperature difference between the fluid and the wall.

Example 1

The following example calculates the convective unit heat flow for air at 25 degrees Celsius going through a pipe at 15 degrees Celsius with a diameter of 0.1 meters. First the Nusselt number is calculated using the Engineering/Heat_Transfer/Convection/Nusselt_intpipe module, then the heat flow is determined based on this value.

#include <codecogs/engineering/heat_transfer/convection/nusselt_intpipe.h>
#include <codecogs/engineering/heat_transfer/convection/flow.h>
#include <stdio.h>
 
int main()
{
  // constants of the problem
  double Pr = 0.71465, Gr = 1356596.6005, 
  lambda = 0.025969, L = 0.1, dT = 10;
 
  printf("\nAir at 25 deg. Celsius\n");
  printf("flowing through a pipe at 15 deg. Celsius\n\n");
 
  double Re1 = 800;
  printf("  Re = %.2lf (laminar flow)\n", Re1);
 
  // compute Nusselt number in the case Re = 800
  double Nu1 = 
  Engineering::Heat_Transfer::Convection::Nusselt_intpipe(Pr, Gr, Re1);
  printf("  Nu = %.4lf\n", Nu1);
 
  // display the unit heat flow
  printf("Flow = %.4lf (W/sq. meters)\n\n",
  Engineering::Heat_Transfer::Convection::flow(lambda, L, dT, Nu1));
 
  double Re2 = 5100;
  printf("  Re = %.2lf (turbulent flow)\n", Re2);
 
  // compute Nusselt number in the case Re = 5100
  double Nu2 =
  Engineering::Heat_Transfer::Convection::Nusselt_intpipe(Pr, Gr, Re2);
  printf("  Nu = %.4lf\n", Nu2);
 
  // display the unit heat flow
  printf("Flow = %.4lf (W/sq. meters)\n\n",
  Engineering::Heat_Transfer::Convection::flow(lambda, L, dT, Nu2));
 
  return 0;
}

Output

Air at 25 deg. Celsius
going through a pipe at 15 deg. Celsius
 
  Re = 800.00 (laminar flow)
  Nu = 4.8374
Flow = 12.5624 (W/sq. meters)
 
  Re = 5100.00 (turbulent flow)
  Nu = 16.8088
Flow = 43.6507 (W/sq. meters)

References

Dan Stefanescu, Mircea Marinescu - "Termotehnica"

Parameters

lambda	the thermal conductivity of the fluid (Watt per meters Kelvin)
L	the characteristic length (meters)
dT	the temperature difference (Kelvin)
Nu	the Nusselt number of the fluid

Returns

the convective heat flow per unit area of a fluid with given parameters (Watt per square meters)

Authors

Grigore Bentea, Lucian Bentea (November 2006)

Source Code

Source code is available when you agree to a GP Licence or buy a Commercial Licence.

Not a member, then Register with CodeCogs. Already a Member, then Login.