modelHANaturalCylinder

Calculates an hA value for natural convection around a cylinder
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Extends from Modelica.Blocks.Icons.Block (Basic graphical layout of input/output block).

Information

This model calculates the convection coefficient h for natural convection from a cylinder submerged in fluid. h is calcualted using Eq 9.34 from Incropera and DeWitt (1996). Output of the block is the hA value.

The Nusselt number is computed as

NuD = (0.6 + (0.387 RaD(1/6))/(1+(0.559 Pr) (9/16))(8/27))2);

where NuD is the Nusselt number, RaD is the Rayleigh number and Pr is the Prandtl number.
This correclation is accurate for RaD less than 1012.

h is then calculated from the Nusselt number. The equation is

h = NuD k/D

where k is the thermal conductivity of the fluid and D is the diameter of the submerged cylinder.

References

Fundamentals of Heat and Mass Transfer (Fourth Edition), Frank Incropera and David DeWitt, John Wiley and Sons, 1996

Parameters

TypeNameDefaultDescription
Modelica.Units.SI.DiameterChaLenCharacteristic length of the cylinder
General › Nominal condition
Modelica.Units.SI.ThermalConductancehA_nominalConvective heat transfer coefficient
Modelica.Units.SI.TemperatureTFlu_nominalFluid temperature at hA_nominal
Modelica.Units.SI.TemperatureTSur_nominalSurface temperature at hA_nominal

Connectors

TypeNameDefaultDescription
Modelica.Blocks.Interfaces.RealInputTSurTemperature of the external surface of the heat exchanger
Modelica.Blocks.Interfaces.RealInputTFluTemperature of the fluid in the heat exchanger
Modelica.Blocks.Interfaces.RealOutputhAhA-value of the heat exchanger

Components

TypeNameDefaultDescription
RealhConvection coefficient

Contents

NameDescription
MediumMedium inside the tank
nusseltprotected

Revisions

  • August 29, 2014 by Michael Wetter:
    Refactored function calls for medium properties.
  • May 10, 2013 by Michael Wetter:
    Revised implementation to use hA_nominal as a parameter, and compute the associated surface area A. This revision was required to have a consistent computation of the hA values inside and outside of the coil in the heat exchanger model of the water tank.
  • February 26, 2013 by Peter Grant:
    First implementation.