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Convection

Lumped thermal element for heat convection

 

Description

Connections

Variables

Initial Conditions

See Also

Description

The Convection component models a linear heat convection between solid geometries and fluid flow over the solid by determining the convective thermal conductance, Gc, by measurements. The basic constitutive equation for convection is

Qflow=GcTsolidTfluid

If Gc is an input value, it may be calculated according to

Gc=hA

where the heat transfer coefficient, h, is calculated from properties of the fluid flowing over the solid.  

Example: Machines cooled by air

     h=7.8 v0.78  Wm2K (forced convection)

        = 12           Wm2K (free convection)

where

      v: Air velocity in m/s

Laminar flow with constant velocity of a fluid along a flat plate where the heat flow rate from the plate to the fluid (= solid.Q flow) is kept constant:

h=Νkx

Ν=0.453 ℜPr13

Connections

Symbol

Units

Description

Gc

WK

Constant thermal convection between the two materials

solid

-

Thermal input port

fluid

-

Thermal output port

Variables

Symbol

Units

Description

h

Wm2K

Heat transfer coefficient

Ν

-

hxk  (Nusselt number)

ℜ

-

vxρμ (Reynolds number)

Pr

-

 cpμk  (Prandtl number)

v

-

Absolute velocity of fluid

x

-

Distance from leading edge of flat plate

ρ

-

Density of fluid (material constant)

μ

-

Dynamic viscosity of fluid (material constant)

cp

-

Specific heat capacity of fluid (material constant)

k

-

Thermal conductivity of fluid (material constant) and the equation for h holds, provided that &real;<5105 and 0..6<Pr<50

W

-

Watts

T

-

Temperature

Initial Conditions

Symbol

Units

Description

Modelica ID

Qflow0

W

Heat flow rate from porta to portb

Q_flow

&Delta;T0

K

Initial temperature difference

dT

See Also

Heat Transfer Components

Thermal Overview

The components described in this topic are from the Modelica Standard Library. To view the original documentation, which includes author and copyright information, click here.

 

 

 

 

 


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