CFD analysis of external aerodynamic and entry into to the air conditioning system on the roof of a bus

Transcription

1 CFD analysis of external aerodynamic and entry into to the air conditioning system on the roof of a bus Samuel Diaz ESSS Argentina Samuel.diaz@esss.com.ar

2 PRESENTATION TOPICS Company Overview; Problem Description; Goals; Methodology; Conclusion.

3 COMPANY OVERVIEW THE ANSYS CHANNEL PARTNER FOR SOUTH AMERICA ANSYS GLOBAL PRESENCE employees 60+ sales offices on 3 continents Network of sales channel partners in 40 countries

4 COMPANY OVERVIEW 19 YEARS OF EXPERIENCE Since 1995 providing the most comprehensive simulation solutions to the market LOCATIONS WHAT WE DO? Reduce product development time Optimize processes Improve product performance USA Houston an ESSS and EnginSoft Partnership Colombia Bogota TEAM PROFILE High-quality services and support to customers Peru Lima Chile Santiago Brazil Florianópolis São Paulo Rio de Janeiro Caxias do Sul Argentina Córdoba

5 COMPANY OVERVIEW SOFTWARE ANSYS modefrontier EnSight VCollab KRAKEN Chimera CONSULTING SERVICES Modeling activities (R&D) Troubleshooting Integration of technologies Value-added services CUSTOM DEVELOPMENT Design of new applications Multiplatform GUI Numerical methods Parallel processing Scientific visualization TRAINING 60+ training courses Postgraduate courses Online courses 900+ attendees per year TECHNICAL SUPPORT Phone Online On-site ACADEMIC PROGRAM Student / Academic & Research Affordable prices Great flexibility Partnership program

6 PROBLEM DESCRIPTION In order to get a good air conditioning condenser performance is very important to have a proper flow pattern and a slow air in the condenser inlet region. Furthermore, the hot gases from exhaust system don t have to be absorbed by the air conditioner. CFD analyses have been done in order to compare the air flow over the region near the air conditioning condenser for two different configurations of the roof and for two different bus velocities.

7 GOALS Air flow analysis over the roof of the Bus; Investigate the air flow over the region near the air conditioning condenser; Compare two different configurations of the roof near the opening on the rear; Study the behavior of the exhaust gases near the condenser.

8 CASES 4 (four) steady state simulations: Case 1: The original geometry of the bus into a stream of air of 100 km/h. Case 2: The same conditions of the Case 1 but with a geometry of the roof modified. Case 3 & 4: Simulation of the rear of the roof with exhaust gases and bus stopped for both geometries.

9 METHODOLOGY The geometry has been simplified in any parts where the shape will not affect the results of the analysis. The shape of the roof has remained exactly the same geometry. Simplified Geometry Original Geometry

10 METHODOLOGY Radiator Fans Simplified Geometry Porous Zone Original Geometry The radiator is modeled as a porous zone with a heat source and the fans with rotating domains. Fan s Rotating Domains Internal Flow

11 METHODOLOGY ANSYS TGrid Wrapper Surface Mesh ANSYS ICEM-CFD Volumetric Mesh Boundary Layer

12 METHODOLOGY ANSYS Meshing for both Surface and Volumetric Mesh

13 METHODOLOGY Operation Conditions: Pressure = 1 atm Temperature = 43 ºC Inlet: Velocity = 100 km/h (case 1 & 2) Velocity = 0 km/h (case 3 & 4) Bus Walls (No-slip condition): Adiabatic walls Outlet (all other zones): Pressure outlet Gauge Pressure = 0 Pa Condenser Inlet Exhaust (Hot Air): Case 1 & 2: Flow: 12,8 kg/min Temp.: 600 ºC Case 3 & 4: Flow: 3,8 kg/min Temp.: 350 ºC Floor (Free slip condition)

14 METHODOLOGY Condenser Inlet (grille modeled like a pressure drop) Radiator (Porous Zone): Heat Source: BTU/hr Condenser Outlet (grille modeled like a pressure drop) Fans (Rotating Domains): Speed: 1920 rpm

15 RESULTS CASE 1: Recirculation

16 RESULTS CASE 2: Strong recirculation

17 RESULTS Condenser Inlet

18 RESULTS CASE 3: 180ºC Iso-surface 120ºC Iso-surface 60ºC Iso-surface CASE 4: 180ºC Iso-surface 120ºC Iso-surface 60ºC Iso-surface

19 RESULTS Condenser Inlet The combustion gases absorbed by the condenser generate higher temperatures in this corner

20 CONCLUSION Case 1 & 2 (both 100 kph) Air flow at the rear of the bus roof was resolved in detail. Significant flow pattern differences were observed as the roof fairing defined the velocity field near the condenser inlet. Condenser volumetric flow for Case 1 (with fairing) is 52% higher in comparison with Case 2 (without fairing). The roof fairing in Case 1 reduces the air speed in the condenser inlet region, creating a favorable stagnation region allowing the condenser fans to work properly.

21 CONCLUSION Case 3 & 4 (both bus stopped) In the roof without fairing, the condenser absorbs part of the hot combustion gases, increasing the temperature in condenser inlet and decreasing its performance. This problem is not observed in the roof fairing because the plume generated by exhaust does not interact with the condenser. Condenser volumetric flow for both cases are similar, the difference between them is less than 5%.

22 Thank you for your attention!! Questions? Ing. Samuel Diaz CAE Division CFD Specialist