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Forced Heat Transfer Check

Accessory component to check the heat transfer coefficient of forced convection

 

Description

Equations

Variables

Connections

Parameters

Initial Conditions

See Also

Description

The Forced Heat Transfer Check component models the heat transfer coefficient calculation of forced convection.

Before using HeatConvection component, you can check how to calculate the heat transfer coefficient internally.

Equations

Average temperature is:

T=Tin1Tin22

 

Heat transfer coefficient of forced convection is calculated with:

h=`HeatTransfer.Properties.Fluid.AirForcedlHeatTransferpin, Tin1,Tin2, Vin,Convection Type, true, 1,1,1,1

( h=NukX )

Output is:

out=h

 

And, Nusselt number Nu is calculated with the following equation which is selected by the option.

 

• 

Default : Use references for Forced = false

If you select this option, the generalized equation is valid.

Nu=CforcedRemforcedoffsetforcedPrnforced

( Re and Pr and k is calculated from pin and T )

 

The default value of the experimental parameters are for the flat plate with the laminar flow.

Nu=0.664Re12Pr13

• 

Reference "Tube and Duct" : Use references for Forced = true and Forced Convection type = Tube and Duct

For laminar flow, the constant Nusselt number is used in this option, and for turbulent, Dittus-Boetter's equation [1] is used.

Nu&equals;&lcub;3.66Re<2300&lcub;0.023Re0.8Pr0.4T1<T20.023Re0.8Pr0.3otherwiseotherwise

( Re and Pr and k is calculated from pin and T )

 

• 

Reference "Over flat plates (Laminar)" : Use references for Forced = true and Forced Convection type = Over flat plates

Nu&equals;0.664Re12Pr13

( Re and Pr and k is calculated from pin and T )

 

• 

Reference "Over a cylinder" : Use references for Forced = true and Forced Convection type = Over a cylinder

This equation is given by Churchill and Bernstein [2], which is valid for the range 102<Re<107, RePr&gt;0.2.

Nu&equals;0.3&plus;0.62Re12Pr131&plus;0.4Pr23141&plus;Re2820005845

( Re and Pr and k is calculated from pin and T )

• 

Reference "Over a sphere" : Use references for Forced = true and Forced Convection type = Over a sphere

This equation is developed by Whitaker [3], which is valid for the range 3.5<Re<8104, 0.7<Pr<380.

Nu&equals;2&plus;0.4Re12&plus;0.06Re23Pr0.4&eta;__f&eta;__s14

&eta;__f&equals;`HeatTransfer.Properties.Fluid.AirViscosity_pT`p&comma; T__f

&eta;__s&equals;`HeatTransfer.Properties.Fluid.AirViscosity_pT`p&comma; T__s

( Re and Pr and k is calculated from pin and T )

 

For information on the calculation of Fluid properties, see Fluid Properties Check.

 

References

[1] : Dittus, F. W. and L. M. K. Boelter, Univ. Calif. (Berkeley) Pub. Eng. vol. 2, p.443, 1930.

[2] : Churchill, S. W., and M. Bernstein. "A Correlating Equation for Forced Convection from Gases and Liquids to a Circular Cylinder in Crossflow", J. Heat Transfer, vol.99, pp.300-306, 1977.

[3] : Whitake, S. "Forced Convection Heat-Transfer Correlations for Flow in Pipes, Past Flat Plates, Single Cylinders, Single Spheres, and Flow in Packed Bids and Tube Bundles", AIChE J., vol.18 p361, 1972.

 

 

Variables

Symbol

Units

Description

Modelica ID

T__

K

Averaged temperature between Tin[1] and Tin[2]

 

h

Wm2K

Heat transfer coefficient

h

Nu

Nusselt number

 

Re

Reynolds number

 

Pr

Prandtl number

 

k

WmK

Thermal conductivity

 

&eta;__s

Pas

Viscosity calculated with temperature of solid port

 

&eta;__f

Pas

Viscosity calculated with temperature of fluid port

 

 

Connections

Name

Units

Condition

Description

Modelica ID

pin

Pa

-

Pressure input

pin

Tin2

K

-

Temperature inputs

Tin[2]

Vin

ms

-

Wind speed

Vin

out

WmK

-

Heat transfer coefficient of Forced convection

out

Parameters

Symbol

Default

Units

Description

Modelica ID

Use reference for Forced

false

If true, all parameters are defined by references.

use_reference_forced

Forced Convection Type

Tube and Duct

Geometry type of forced convection as references

ForcedConvecType

X

1.0

m

Streamwise length

X

Cforced 

0.664

Gain parameter for Reynolds number in the generalized experimental equation of Forced convection generalized equation.

C_forced

mforced

12

Exponent parameter for Reynolds number in the generalized experimental equation of Forced convection generalized equation.

m_forced

offsetforced

0

Offset parameter for Reynolds number in the generalized experimental equation of Forced convection generalized equation.

offset_forced

nforced

13

Exponent parameter for Prandtl number in the generalized experimental equation of Forced convection generalized equation.

n_forced

Initial Conditions

Symbol

Units

Description

Modelica ID

T__0 

K

Initial condition of the averaged temperature

T(0)

See Also

Heat Transfer Library Overview

Properties Overview