Defining Physics and Conditions

The physics and conditions are specified as follows:

Modules

Click Select Modules in the Model Panel. The Physical Model Selection dialog box opens.
Fan_mrf_fan_1, Heat, Vehicle, Flow and Turbulence are automatically added to the Model Panel by the Vehicle Template Mesher.
Select Radiation under Available Modules and click add Radiation to the Simulation Module.
Click Close to close the Physical Model Selection dialog box.

Figure 17.1 - Adding Modules

Operating Parameters

Fan

Select Fan mrf_fan_1 in the Model Panel.
Select Counterclockwise from the Rotational Direction drop-down list in the Model Tab of Properties Panel.
Enter 500 rpm for Rotational Speed.

Figure 17.2 - Fan module parameters

Vehicle

Select Vehicle in the Model Panel.
Enter 25 m/s for Wind Speed.
Enter 101325 Pa for Environment Pressure.

Figure 17.3 - Vehicle module parameters

Heat Module

Select Heat in the Model Panel.
Select Extended Mode drop-down list in the Model Tab of Properties Panel.
Enter Temperature Upper Limit as 1200 K.
Enter Temperature Lower Limit as 300 K.

Figure 17.4 - Heat module parameters

Radiation

Select Radiation in the Model Panel.
Select Extended Mode drop-down list in the Model Tab of Properties Panel.
Enter 0.1 for Converge Criterion and 4 for Grain Size in the Model Tab of Properties Panel.

Figure 17.5 - Radiation module parameters

Global Expression

Click Edit Expression icon on the View Toolbar to open the Expression Editor dialog box.
Copy and paste the expressions written under Description drop-down list for Global Expressions, see Figure 17.6.

Click OK to close the Expression Editor dialog box.

Figure 17.6 - Global Expressions

Fluid (air) properties

Select exhaust_muffler_v2, fan_mrf, radiator, vehicle Volumes in the Geometric Entities Panel.
Select Ideal Gas Law from the Density drop-down list under Common in the Model Tab in the Properties Panel.
Enter muAir Pa-s for Dynamic Viscosity in Property list under Vehicle.
Select Constant Conductivity under Conductivity drop-down of Heat list.
Enter kAir W/m-K for Conductivity.
Select Cp Polynomial Function of T under Enthalpy Model drop-down list.
Enter 978.285 J/kg-K for Capacity at Reference T.
Enter 0.094 J/kg-K² for Linear Temperature Coefficient.

Figure 17.7 - Fluid (air) properties

Radiator (air) properties

Select radiator under Volumes in the Geometric Entities Panel.
Select Model Tab in the Properties Panel.
Enter the following parameters under Vehicle for Resistance Model.

Resistance Model: Pressure Loss
Material Structure: One flow direction
Flow Direction: 1, 0, 0
Linear Drag Coefficient: 100 Pa-s/m²
Quadratic Drag Coefficient: 100 1/m

Select Two Fluid Heat Exchanger from the Heat Exchanger drop-down list and select Yes for Primary Fluid under the Heat list.

Figure 17.8 - Radiator (air) properties

´	Note: For calculation of Linear Drag Coefficient and Quadratic Drag Coefficient, refer Template.

Radiator (Coolant) properties

Select radiator_linked under Volumes in the Geometric Entities Panel.
Select Model Tab in the Properties Panel.
Enter the Value = 1022 kg/m³ under Density for the Common list.
Enter the parameters for Property list under Flow as follows:

Dynamic Viscosity: 0.0007 Pa-s

Enter the following parameters under Heat as follows:

Constant Conductivity: 0.0416 W/m-K
Constant Capacity: 3600 J/kg-K

Select Two Fluid Heat Exchanger from the Heat Exchanger drop-down list under the Heat list.

Select Specified Heat Rejection from the Heat Input drop-down list under the Heat Exchanger list.

Enter the following under Heat Exchanger drop-down list of Heat module.

Specified Heat Rejection: 30 kW
NTU: rad_ntu

Figure 17.9 - Radiator (Coolant) properties

Solid Properties

Select Volumes exhaust_catalytic_converter, exhaust_muffler_v1, exhaust_pipe_1, exhaust_pipe_2, exhaust_tail_pipe_1, exhaust_tail_pipe_2 and fuel_tank in the Geometric Entities Panel.
Select Blanked for State drop-down list under Flow.
Enter the the properties for the solids as shown in Table 17.1.

Figure 17.10 - Solid properties - Exhaust

Volumes	Density (kg/m³)	Conductivity (W/m-K)	Capacity (J/kg-K)
exhaust_catalytic_converter, exhaust_muffler_v1, exhaust_pipe_1, exhaust_pipe_2, exhaust_tail_pipe_1, exhaust_tail_pipe_2	7610	16.5	503
fuel_tank	1600	0.25	1200

Volumes

Density (kg/m³)

Conductivity (W/m-K)

Capacity (J/kg-K)

exhaust_catalytic_converter,

exhaust_muffler_v1,

exhaust_pipe_1,

exhaust_pipe_2,

exhaust_tail_pipe_1,

exhaust_tail_pipe_2

7610

16.5

503

fuel_tank

1600

0.25

1200

Table 17.1 - Solid properties

Boundary conditions

Some boundary conditions for the simulation are automatically set by the Vehicle template:

Figure 17.11 - Vehicle Inlet

Figure 17.12 - Vehicle Outlet

Remaining boundary conditions are specified as follows:

Vehicle Boundaries

Select engine from the Boundaries list under Volumes in the Geometric Entities Panel.
Select Specified Temperature from the Heat drop-down list and enter 95 C for Temperature in the Model Tab in the Properties Panel.
Figure 17.13 - Engine Surface Temperature

Figure 17.14 - Exhaust Surface Temperature
Select engine_exhaust from the Boundaries list under Volumes in the Geometric Entities Panel.
Select Specified Temperature from the Heat drop-down list and enter 600 C for Temperature in the Model Tab in the Properties Panel.
Select engine_transmission from the Boundaries list under Volumes in the Geometric Entities Panel.
Select Specified Temperature from the Heat drop-down list and enter 50 C for Temperature in the Model Tab in the Properties Panel.
Select all Boundaries, except vehicle_floor, vehicle_inlet, vehicle_outlet, vehicle_roof, vehicle_side1 and vehicle_side2 from the Boundaries list under Vehicle Volumes in the Geometric Entities Panel.
Enter 0.9 for Emissivity under the Options drop-down list.
Select Interfaces exhaust_catalytic_converter, exhaust_muffler, exhaust_pipe_1, exhaust_pipe_2, exhaust_tail_pipe_1 and exhaust_tail_pipe_2 from the Interfaces list under Vehicle Volumes in the Geometric Entities Panel.
Enter 0.7 for Emissivity under the Options drop-down list.
Select Interfaces fuel_tank from the Interfaces list under Vehicle Volumes in the Geometric Entities Panel.
Enter 0.9 for Emissivity under the Options drop-down list.

Figure 17.15 - Example for assigning Emissivity

Exhaust Inlet

Select exhaust_inlet from the Interface list under Volumes in the Geometric Entities Panel.
Select Specified Interface option under Operation list in Split/Combine Geometry or Grid in the Mesh Panel. Click Seperate Interface. It generates two boundaries (exhaust_inlet_i1 and exhaust_inlet_i2) under exhaust_muffler_v2 and vehicle Volumes separately.
Select exhaust_inlet_i1 from the Boundaries list under Volumes in the Geometric Entities Panel.
Select Specified Mass Flux from the Flow drop-down list and enter 0.04 kg/s for Mass Flux in the Model Tab in the Properties Panel.
Select Specified Temperature from the Heat drop-down list and enter 700 C for Temperature in the Model Tab in the Properties Panel.

Figure 17.16 - Exhaust Inlet Boundary condition

Radiator (Coolant) Boundaries

Select radiator_dir1_min_linked from the Boundaries list under Volumes in the Geometric Entities Panel.
Select Specified Volumetric Flux option from the Flow drop-down list and enter 60 L/min for Volumetric Flux in the Model Tab in the Properties Panel.
Select Yes for Temperature, Total Flux under the Output for Heat drop-down list.
Figure 17.17 - Coolant Inlet Boundary condition
Select radiator_dir1_max_linked from the Boundaries list under Volumes in the Geometric Entities Panel.
Select Specified Pressure Outlet from the Flow drop-down list and enter 101325 Pa for Pressure in the Model Tab in the Properties Panel.
Select Yes for Temperature, Total Flux under the Output for Heat drop-down list.

Figure 17.18 - Coolant Outlet Boundary condition

´	Note: Select Yes for Temperature and Min/Max Temperature under Output list for Heat list of all Volumes. Select Yes for Total flux Output under Heat list for radiator Volume interfaces (MGI01 and MGI02).