cfd analysis of external aerodynamic and entry into to the ... · cfd analysis of external...
TRANSCRIPT
CFD analysis of external aerodynamic and
entry into to the air conditioning system
on the roof of a bus
Samuel Diaz – ESSS Argentina
PRESENTATION TOPICS
• Company Overview;
• Problem Description;
• Goals;
• Methodology;
• Conclusion.
COMPANY OVERVIEW
THE ANSYS CHANNEL PARTNER FOR SOUTH AMERICA
ANSYS GLOBAL PRESENCE
• 1.600 employees
• 60+ sales offices on 3 continents
• Network of sales channel partners in 40 countries
COMPANY OVERVIEW
Brazil • Florianópolis
• São Paulo
• Rio de Janeiro
• Caxias do Sul
Argentina • Córdoba
Colombia • Bogota
Peru • Lima
USA • Houston
an ESSS and EnginSoft Partnership
Chile • Santiago
19 YEARS OF EXPERIENCE Since 1995 providing the most comprehensive
simulation solutions to the market
WHAT WE DO? • Reduce product development time
• Optimize processes
• Improve product performance
TEAM PROFILE High-quality services and support to customers
LOCATIONS
COMPANY OVERVIEW
TECHNICAL SUPPORT • Phone
• Online
• On-site
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
ACADEMIC PROGRAM • Student / Academic & Research
• Affordable prices
• Great flexibility
• Partnership program
TRAINING • 60+ training courses
• Postgraduate courses
• Online courses
• 900+ attendees per year
SOFTWARE • ANSYS
• modeFRONTIER
• EnSight
• VCollab
• KRAKEN
• Chimera
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.
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.
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.
METHODOLOGY
Original Geometry
Simplified Geometry
• 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.
METHODOLOGY
Original Geometry
Internal Flow
Simplified Geometry
The radiator is modeled as a porous zone with a
heat source and the fans with rotating domains.
Radiator Fans
Porous Zone
Fan’s
Rotating
Domains
METHODOLOGY
ANSYS TGrid Wrapper Surface Mesh
ANSYS ICEM-CFD Volumetric Mesh
Boundary Layer
ANSYS Meshing for both Surface and
Volumetric Mesh
METHODOLOGY
METHODOLOGY
Condenser Inlet
Inlet:
Velocity = 100 km/h (case 1 & 2)
Velocity = 0 km/h (case 3 & 4)
Bus Walls (No-slip condition):
Adiabatic walls
Operation Conditions:
Pressure = 1 atm
Temperature = 43 ºC
Floor (Free slip condition)
Outlet (all other zones):
Pressure outlet Gauge Pressure = 0 Pa
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
METHODOLOGY
Condenser Inlet
(grille modeled like a pressure drop)
Condenser Outlet
(grille modeled like
a pressure drop)
Radiator (Porous Zone):
Heat Source: 108000 BTU/hr
Fans (Rotating Domains):
Speed: 1920 rpm
RESULTS
Recirculation
CASE 1:
RESULTS
CASE 2:
Strong
recirculation
RESULTS
Condenser Inlet
RESULTS
180ºC Iso-surface 120ºC Iso-surface 60ºC Iso-surface
180ºC Iso-surface 120ºC Iso-surface 60ºC Iso-surface
CASE 3:
CASE 4:
RESULTS
Condenser Inlet
The combustion gases
absorbed by the condenser
generate higher temperatures
in this corner
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.
• 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%.
CONCLUSION
Thank you for your attention !!
Questions?
Ing. Samuel Diaz CAE Division – CFD Specialist