Kessler ESSS-Fiat.ppt - Ansys · 7/24/2009 3 Goals • Develop and implement a computational model to evaluate the main flow characteristics on the interior of a passenger car HVAC

7/24/2009

1

CFD study of a passenger car HVAC system

CFD study of a passenger car HVAC system

Marcelo KrugerVictor Arume de SouzaRegis AtaidesMartin KesslerCesareo de La Rosa Siqueira

Gustavo Maia Vinicius Leal

EASC 20094th European Automotive Simulation Conference

Munich, Germany6-7 July 2009

1

7/24/2009

2

Agenda

• IntroductionG l• Goals

• Computational model • Geometry

• Mesh• Boundary condition

• Results• Remarks

Introduction

• Following Hucho et al (“Aerodynamics of Road Vehicles”),every consideration of air conditioning of cars must befocused on its occupants In this sense thermal comfortfocused on its occupants. In this sense, thermal comfortinside a vehicle is a major concern in automotive industry.

• In tropical countries, such as Brazil, car HVAC systemshould guarantee a comfortable environment for the

4

gpassengers, and specially for the driver, his/her alertnessand ability to concentrate on traffic depends on this level ofcomfort.



2

7/24/2009

3

Goals• Develop and implement a computational model to evaluate

the main flow characteristics on the interior of a passengercar HVAC system;y

• Based on the model, study the temperature rise that airexperiments when passing through the duct system,influenced by the heat that stems from the engine, fordifferent mass flow rates;

5

• Determine how much the mass flow rate influence thetemperature at the outlet.

Computational Model - Geometry

1st RegionAir Inlet

2nd Region

6

3rd Region



3

7/24/2009

4

Computational Model - Geometry

Inlet grid

7

g

• Hybrid Mesh: tetrahedral + prisms

Computational Model - Mesh

tetrahedral + prisms

About 4,8 millions of elements 8



4

7/24/2009

5

– Steady state flow;– Incompressible;

Computational Model - Hypotheses

– Turbulent;

• Fluid properties: AirD it 1 225 [k / 3]

9

– Density: 1,225 [kg/m3]– Viscosity: 1,7894e-05 [kg/m s]

• Inlet mass flow:

Computational Model – Boundary Conditions

M d l I l t fl ( ³/h)Model Inlet mass flow (m³/h)Case 1 228Case 2 260Case 3 290Case 4 320

• Inlet temperature: 26.85°C (300 K)• Outlet with atmospheric pressure

10



5

7/24/2009

6


• Prescribed temperature (experimental) on the walls

2nd RegionPosition Temperature [ºC]

Point 31 50,9Point 32 46,5Point 33 48,5Point 34 45,3Point 35 49,3Point 36 48,8

P i t 37

2nd Region

1st Region

11

Point 37 -Point 38 53,5Point 39 47,2Point 40 42,4Point 41 50,6

3rd Region


• Prescribed temperature (experimental) on the walls

Position Temperature [ºC]Point 01 44,6Point 02 46,7Point 03 48,5Point 04 45,8Point 05 46,4Point 06 49,8Point 07 51,8Point 08 49,3Point 09 47,0Point 10 49,3

3rd Region

12

Point 10 49,3Point 11 49,6Point 12 50,4Point 13 51,0Point 14 49,6Point 15 48,1Point 16 46,9Point 17 47,0



6

7/24/2009

7

Results

• Fluid flow features evaluated:• Velocity field to identify recirculation areas zones of• Velocity field – to identify recirculation areas, zones of “death” (low velocities) volume, where the fluid could be for a long time, increasing the temperature;

• Streamlines;

• Temperature field;

13

Results – Velocity field228m3/h 260m3/h

320m3/h290m3/h

m/s



7

7/24/2009

8

Results – Velocity Vectors at outlet

4228m3/h 260m3/h

15

320m3/h290m3/h

Results – Temperature field

228m3/h 260m3/h

16

320m3/h290m3/h



8

7/24/2009

9

Results – Heat Transfer

[m3/h]

Heat transfer in the walls

Outlet Average Temperature

Mass flow

1071.3137.87290

981.0938.08260

881.4538.35228

[W][°C][m /h]

1159.3037.71320

• Inlet Temperature = 26.85°C (300K)

Results – Streamlines

4228m3/h 260m3/h

18

320m3/h290m3/h



9

7/24/2009

10

Results

[W][ 3/h]

Heat transfer variationHeat Transfer Mass flow variation

Mass flow

21.51071.3127290

11.3981.0914260

-881.45-228

%[W]%[m3/h]

31.51159.3040320

• The flux of 228 m3/h has been used as the reference.

Remarks

• The development of the numerical model allowed to betterunderstand the flow behavior inside the HVAC system;

f f f f CThe influence of mass flow on heat transfer inside the HVACsystem has been evaluated;

• The streamlines and temperature field at outlet have shownvery similar behaviour for all configurations;

• The velocity vectors and streamlines indicated somei l ti th t ld b ibl f i i f

20

recirculation areas, that could be responsible for increasing oftemperature;



10

7/24/2009

11

Remarks

• The outlet average temperature indicated an increasingof 11°C comparing with the inlet temperature;

• The temperature variation at the outlet suffered little• The temperature variation at the outlet suffered littleinfluence due to variation on mass flow rate. For all fourmass flow rates considered (40% change between thesmaller and the larger mass flow rates) the averagetemperature at the outlet stayed within one degree Celsiusrange.

Th h f h h h d h d

21

• The heat transfer, on the other hand, changedsignificantly due to mass flow rate: the heat transfersuffered an increase of around 31% between the smallerand the larger mass flow rate.

Th k !Thanks!Contact:

Marcelo Krugerkruger@esss com [email protected]



11

Documents

Kessler ESSS-Fiat.ppt - Ansys · 7/24/2009 3 Goals • Develop and implement a computational model to evaluate the main flow characteristics on the interior of a passenger car HVAC