Understanding ducts and area definition

The way you define a duct cross section in Simcenter 3D Thermal/Flow, Simcenter 3D Electronic Systems Cooling, or Simcenter 3D Space Systems Thermal, varies according to the 1D mesh collector type that you use.

• The Duct type of 1D mesh collector lets you select any cross section area types from the Section Manager.

• The Duct Axisymmetric type of 1D mesh collector needs a thickness that you define using the Duct physical property.

• The Duct with Thick Walls type of 1D mesh collector lets you select only hollow cross section types from the Section Manager.

• The Duct with Mass Flow and Duct with Mass Flow Axisymmetric types of 1D mesh collectors do not need a cross section definition.

The thermal solver interprets the cross section that is defined in the Section Manager differently depending on the mesh collector that you use. For example:

Area definitionDuct typeDuct with Thick Walls typeNot Allowable	Area definition	Duct type	Duct with Thick Walls type			Not Allowable
Area definition	Duct type	Duct with Thick Walls type
		Not Allowable
Fluid area, Aduct	Wall area, Awall

Cross section solver definition for ducts, ducts with thick walls, and beams

The options available in the Beam Section dialog box allow for almost any type of area cross section.

You can define any Beam Section type to model a duct shape. When you solve the model, the solver reduces all sections to the following values:

• Fluid cross section area, Aduct

• Wetted perimeter of fluid cross section area, Pduct

• Hydraulic diameter, DH = 4Aduct/Pduct

• Thickness of the wall, twall

• External perimeter of the wall cross section area, Pwall

• Wall cross section area, Awall = (Pwall+Pduct)/2twall

However, when you define a beam section using the User Defined Properties type, no calculation is done and the values you type are used directly.

• Solid Area = Awall

• Fluid Area = Aduct

• External Perimeter = Pwall

• Wetted Perimeter = Pduct

These values are used in the calculation of either duct fluid flow or convection and radiation from the walls of the duct to the environment. You must define these values congruently with the physics of the model.

Note:

When you use Face of Solid and General Geometry section properties, only the section area is exported as the solid area property. External perimeter, fluid area, and wetted perimeter are zero. Therefore, do not use Face of Solid and General Geometry types.

Cross section solver definition for axisymmetric ducts

The axisymmetric duct elements simulate annular flow.

For the Duct Axisymmetric type of 1D mesh collectors, you define the radius of the duct, r, by specifying the revolve axis, and the thickness of the duct, t, by defining the Duct physical property.

The solver calculates the section values as follows:Fluid cross section area, Aduct = 2πr**tPerimeter of fluid cross section area, Pduct = 4πrHydraulic diameter,DH = 4Aduct/ Pduct = 2t

How do I

Create a duct flow network

Create a thick wall duct flow network

Create a pressureless duct network

Create a duct flow network and model heat transfer using 2D shells

Create a duct flow network and model heat transfer using 3D solid elements

Connect the duct network to the 3D flow domain

Learn more

1D duct flow networks

Duct analysis workflow

Duct Flow Boundary Conditions

1D meshing

Ensuring consistent 1D element orientation during mesh creation

Creating beam cross sections

Specifying cross sections for 1D elements (Simcenter 3D Thermal/Flow, Electronic Systems Cooling, and Space Systems Thermal)

Look up more details

Modeling ducts with 1D elements

Modeling ducts and their walls with 1D elements

Modeling ducts with 1D elements and their walls with 2D elements

Modeling the interface between ducts and 3D fluid elements

Modeling ducts inside 3D solid elements

Solver calculation for duct elements

Solver calculation for duct with mass flow elements

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Understanding ducts and area definition, Simcenter 3D 2021.1 Series

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