heat transfer, and fatigue in product design uk/staticassets... · response and fatigue in...
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© 2010 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary© 2010 ANSYS, Inc. All rights reserved. 1 ANSYS, Inc. Proprietary
Assessing & Optimising
Heat Transfer,
Structural Response
and Fatigue in
Mechanical Engineering
Product Design
Nigel Atkinson
ANSYS UK Ltd
Introduction
© 2010 ANSYS, Inc. All rights reserved. 2 ANSYS, Inc. Proprietary
Invitation
There are many challenges facing mechanical engineers as they strive to
maximise the performance of heat exchanging equipment and to meet
more demanding thermal management objectives. Typical requirements
are to:
• Improve heat exchange
• Optimise cooling
• Reduce peak-temperatures
• Increase product efficiency
The seminar will introduce the unique capabilities of the ANSYS product
suite to perform integrated flow, thermal, stress and fatigue analysis,
giving mechanical engineers the simulation tools they need to deliver
better performing designs, in shortened development times with
reduced development costs.
Many industrial situations
• Reduce power consumption
• Ensure structural integrity
• Minimise material costs
• Reduce equipment dimensions
© 2010 ANSYS, Inc. All rights reserved. 3 ANSYS, Inc. Proprietary
Today’s Agenda
14.00 – 14.05Introduction and WelcomeNigel Atkinson, ANSYS UK
14.05 – 14.20
Overview of the ANSYS Engineering Simulation Software Suite:- ANSYS CFD to calculate flow distributions, pressure drops and conjugate heat transfer
including convection, conduction and thermal radiation
- ANSYS Mechanical to calculate both thermal stressing and structural fatigue
- The Workbench environment to facilitate integrated multidisciplinary simulation
Mark Leddin & Paul Everitt, ANSYS UK
14.20 – 14.30
Improving CFD Predictions of Heat Transfer- Near-wall mesh refinement
- Advanced turbulence modelling methods
Paul Everitt, ANSYS UK,
14.30 – 15.15
Case Studies- Heat exchangers and boilers
- Cooling jacket
- Radiators
- Waste heat recovery unit
- Thermal battery
- Electronics thermal management
- Other miscellaneous applications
Mark Leddin & Paul Everitt, ANSYS UK
15.15 – 15.30 Coffee Break
15.30 – 16.15Software Demonstration of Integrated Fluid Flow, Thermal Stressing and Fatigue Analysis
on Heat Exchanging DeviceMark Leddin & Paul Everitt, ANSYS UK
16.15 Summary and Q&A
© 2010 ANSYS, Inc. All rights reserved. 4 ANSYS, Inc. Proprietary
ANSYS, The Company
• ANSYS are the world’s largest CAE
Company
• We design, develop, market
and globally support a
wide range of Engineering
simulation software
• Over 1600 people worldwide,
Over 150 in the UK
• A suite of multi-purpose
software technologies for
– Structural Mechanics
– Fluid Dynamics
– Heat Transfer
– Electronics
– Electromagnetics
– Multiphysics
© 2010 ANSYS, Inc. All rights reserved. 5 ANSYS, Inc. Proprietary
Simulation Driven Product Development
Customer needs
Business drivers
Technology trends10X–100X
Productivity
Gain
• Instead of just using
engineering simulation for
verification or trouble-shooting,
many companies are turning to
Simulation Driven Product
Development (SDPD)
– Design, simulate, optimize
– Physically test only the
best candidates
• The benefits of SDPD
– Better performing products
– Shorter development times
– Reduced development
costs
© 2010 ANSYS, Inc. All rights reserved. 6 ANSYS, Inc. Proprietary
ANSYS Portfolio
• ANSYS offer a
full suite of
single-physics
applications
• They are integrated
using the
Workbench
Environment
• The Workbench
environment
enables consistent
model setup, direct
geometry access,
scripting,
parametric design
optimisation and
automated updates
© 2010 ANSYS, Inc. All rights reserved. 7 ANSYS, Inc. Proprietary
Workbench
• Workbench is a project environment that
offers process chaining, management and
scripting
© 2010 ANSYS, Inc. All rights reserved. 8 ANSYS, Inc. Proprietary
Workbench Efficiencies
• Use one instance of the geometry
• Carry out analyses in parallel
• Chain Processes
• Geometry Update
ripples through all
Analysis instances
• No intermediate
file transfers
to manage Electric Steady-State Thermal Static Structural
© 2010 ANSYS, Inc. All rights reserved. 9 ANSYS, Inc. Proprietary
Parametric By Design
Input parameter created from an
expression in ANSYS CFX
Output parameters created from an
expression in ANSYS CFD-Post
Parameter definition in Mechanical
Simulation (implicit, explicit, MBD)
Parameter definition
based on ANSYS
Mechanical APDL
input files
Input parameter created from an
expression in ANSYS FLUENT
Parameter definition
based on linked
Microsoft Excel cells
© 2010 ANSYS, Inc. All rights reserved. 10 ANSYS, Inc. Proprietary
Six-Sigma & Optimisation
• ANSYS DesignXplorer is a tool
that provides all necessary tools
for Design exploration:
– Response surfaces
– Six-Sigma analysis
– Optimization techniques
• ANSYS DesignXplorer is fully
embedded in ANSYS Workbench
and works from the parameter
set definition, regardless of the
complexity of the simulation
© 2010 ANSYS, Inc. All rights reserved. 11 ANSYS, Inc. Proprietary
Today’s Agenda
14.00 – 14.05Introduction and WelcomeNigel Atkinson, ANSYS UK
14.05 – 14.20
Overview of the ANSYS Engineering Simulation Software Suite:
- ANSYS CFD to calculate flow distributions, pressure drops and conjugate heat transfer
including convection, conduction and thermal radiation
- ANSYS Mechanical to calculate both thermal stressing and structural fatigue
- The Workbench environment to facilitate integrated multidisciplinary simulationMark Leddin & Paul Everitt, ANSYS UK
14.20 – 14.30
Improving CFD Predictions of Heat Transfer
- Near-wall mesh refinement
- Advanced turbulence modelling methodsPaul Everitt, ANSYS UK,
14.30 – 15.15
Case Studies
- Heat exchangers and boilers
- Cooling jacket
- Radiators
- Waste heat recovery unit
- Thermal battery
- Electronics thermal management
- Other miscellaneous applicationsMark Leddin & Paul Everitt, ANSYS UK
15.15 – 15.30 Coffee Break
15.30 – 16.15Software Demonstration of Integrated Fluid Flow, Thermal Stressing and
Fatigue Analysis on Heat Exchanging DeviceMark Leddin & Paul Everitt, ANSYS UK
16.15 Summary and Q&A
© 2010 ANSYS, Inc. All rights reserved. 12 ANSYS, Inc. Proprietary© 2010 ANSYS, Inc. All rights reserved. 12 ANSYS, Inc. Proprietary
Assessing and
Optimising Heat
Transfer, Structural
Response and Fatigue
in Mechanical
Engineering Product
Design
14th
June 2011
Paul Everitt
Mark Leddin
ANSYS UK Ltd
© 2010 ANSYS, Inc. All rights reserved. 14 ANSYS, Inc. Proprietary
Overview of the ANSYS Engineering
Simulation Software Suite
ANSYS Mechanical ANSYS CFD
Conduction Yes Yes
Thermal radiation Yes Yes
Convective losses at surfaces Yes Yes
Convection No Yes
Simultaneous flow, conduction, radiation No Yes
Thermal (and mechanical) stressing Yes No
ANSYS CFD
Solid
Fluid
ANSYS MechanicalConvective heat flux or heat
transfer coefficient
Solid
Advantage is that CFD
software calculates heat
flux from fluid to solid
No need to specify htc
or heat flux from fluid to
solid
CFD also provides
insight into fluid flow
© 2010 ANSYS, Inc. All rights reserved. 15 ANSYS, Inc. Proprietary
Heat Transfer Classification
• Three types of convection.
– Natural Convection – Fluid moves
due to buoyancy effects
– Forced Convection – Flow is
induced by some external means.
– Boiling Convection – Body is hot
enough to cause fluid phase change
• Difficult to accurately specify valid htc or
heat flux for complex geometry/flow
– So let CFD calculate the heat flux
3/14/1 , ThTh
)( Tfh
2Th
Typical
values of h
(W/m2·K)
4 – 4,000
80 – 75,000
300 – 900,000
hotT
hotTcoldT
hotT
coldT
coldT
© 2010 ANSYS, Inc. All rights reserved. 16 ANSYS, Inc. Proprietary
Improving CFD Predictions of Heat Transfer -
Thermal Boundary Layer Flow
• Analogous to the viscous boundary layer that develops, there is also a
thermal boundary layer.
• In most industrial applications, free and forced convection occur
simultaneously. The relative magnitude of these effects can be determined
by using a modified Froude number, Fr.
<< 1 Forced convection dominates
≈ 1 Natural and Forced convection are important
>> 1 Natural convection dominates
22Re
GrFr
U
TLg
y
UT ,
T)(yT
)(yU
Viscous
Boundary
Layer
Thermal
Boundary
Layer
wT
© 2010 ANSYS, Inc. All rights reserved. 17 ANSYS, Inc. Proprietary
• Require special approach to capture thermal as well as
viscous boundary layers
– Meshing• Automated Boundary Layer Inflation
methods built-in to ANSYS Meshing
• Can control:
– Number of layers
– First cell height (y+ setting)
– Total Height
– Aspect ratio
– Smooth Transition
– Surface it “inflates” from
• Compatible with all methods and element shapes
Improving CFD Predictions of Heat Transfer -
Thermal Boundary Layer Flow
© 2010 ANSYS, Inc. All rights reserved. 18 ANSYS, Inc. Proprietary
• Require special approach to capture thermal as well as
viscous boundary layers
– Turbulent Models
• Omega based Low Reynolds number turbulence
models
– suitable for near wall
• Can including turbulent transition effects
– Automatic Wall function
• Fine near wall mesh use k-omega
• Coarse near wall use wall functions
• Automatic switch
– Can model conduction through „thin‟ walls
as well
• Includes films/coatings and thermal contact
Improving CFD Predictions of Heat Transfer -
Thermal Boundary Layer Flow
© 2010 ANSYS, Inc. All rights reserved. 19 ANSYS, Inc. Proprietary
Feeding temperature (and pressure) results from
ANSYS CFD as a load into ANSYS Mechanical
• In many situations, it is advantageous to use ANSYS
CFD in tandem with ANSYS Mechanical
– Typically flow and conduction in ANSYS CFD followed
by thermal and mechanical stressing in ANSYS
Mechanical
• There are multiple options for exchanging results
between ANSYS CFD and Mechanical software
– One-way transfer
• Unidirectional interaction between fields in fluids and solid domains
– Two-way transfer
• Bidirectional interaction between fields in fluids and solid domains
© 2010 ANSYS, Inc. All rights reserved. 21 ANSYS, Inc. Proprietary
Example 1: Hot and cold water T-
junction
• ANSYS CFD is used to calculate the mixing of hot and cold
water in a T-junction as well as to assess temperature in solid.
• The 3D temperatures in the solids are passed to ANSYS
Mechanical
• ANSYS Mechanical is then used to assess structural stresses
and deformation under thermal loads.
© 2010 ANSYS, Inc. All rights reserved. 22 ANSYS, Inc. Proprietary
Hot and cold water T-junction
• Hot water from bottom and cold water from side pipe
• Conduction as well as flow included in CFD analysis
110 [bar]
10 [m/s]
20 [C]
10 [m/s]
80 [C]
© 2010 ANSYS, Inc. All rights reserved. 23 ANSYS, Inc. Proprietary
Hot and cold water T-junction
• Hot water from bottom and cold water from side pipe
• Conduction as well as flow included in CFD analysis
Mixing of hot and
cold water StreamlinesMetal
temperatures
© 2010 ANSYS, Inc. All rights reserved. 24 ANSYS, Inc. Proprietary
Hot and cold water T-junction
• Solid temperatures passed to ANSYS Mechanical and
FE analysis performed to calculate deformation and
stress
Thermal stressDeformation
© 2010 ANSYS, Inc. All rights reserved. 25 ANSYS, Inc. Proprietary
Example 2: Air Brake Valve
Flow calculation performed in ANSYS CFD
Pressure on valve passed to ANSYS Mechanical
ANSYS Mechanical calculates valve deflection
• Another typical one-way transfer from ANSYS CFD to ANSYS
Mechanical are pressure loadings
• Airbrake example where ANSYS CFD used to simulate flow
through airbrake to calculate flow distribution and to assess
pressure loading on valve. ANSYS Mechanical then used to
assess structural deformation due to aerodynamic loading.
© 2010 ANSYS, Inc. All rights reserved. 26 ANSYS, Inc. Proprietary
Case studies and software
demonstration
• For the rest of the session, we’d like to present
– Case-studies where ANSYS CFD has been used standalone or in
tandem with ANSYS Mechanical to analyse heat transfer
• Waste heat recovery unit
• Water jacket
• Plate heat exchanger
• Electronics thermal management
• Exhaust system
• I-beam integrity
• Customer project “yoomi”, Intelligent Fluid Solutions Ltd
• Software demonstration of flow, heat transfer, thermal stressing and
fatigue modelling in ANSYS 13.0
© 2010 ANSYS, Inc. All rights reserved. 27 ANSYS, Inc. Proprietary© 2010 ANSYS, Inc. All rights reserved. 27 ANSYS, Inc. Proprietary
yoomi
CFD Behind the Product
Dr. Andrej Horvat
Intelligent Fluid Solutions Ltd.
© 2010 ANSYS, Inc. All rights reserved. 28 ANSYS, Inc. Proprietary
yoomi - CFD Behind the Product
yoomi is a rechargeable, BPA-free, self-
warming baby bottle that warms baby's feed
to the natural temperature of breast milk at
the touch of a button (www.yoomi.com)
• The yoomi bottle design was developed by
Intelligent Fluid Solutions Ltd. between
2007 and 2009.
• Yoomi is being manufactured by Feed Me
Bottles Ltd. in China, South Africa and
UK.
• The yoomi bottle entered the UK market in
Nov. 2009 through John Lewis and is now
also available in Mothercare & Boots.
• Yoomi is expanding internationally and is
available in Scandinavia, Ireland and
continental Europe.
© 2010 ANSYS, Inc. All rights reserved. 29 ANSYS, Inc. Proprietary
yoomi - CFD Behind the Product
• The bottle exploits the subcooled nature
of sodium acetate mixture, which remains
liquid below its solidification temperature
• The mixture is contained inside a warming
unit with channels for the milk flow
• When the solidification process is triggered,
latent heat is released
• As the milk flows along the channels, it is
heated to the correct temperature - above
32oC
• The warmer is recharged by placing it in
boiling water or a steam sterilizer.
© 2010 ANSYS, Inc. All rights reserved. 30 ANSYS, Inc. Proprietary
yoomi - CFD Behind the Product
0.5l2
l1 w
• In order to improve the heat transfer from the
warmer to the milk flow, the milk travelling
time or the channel distance were maximized
• CFD was used to analyse a number of
channel designs in order to obtain a heat
transfer coefficient correlation h (x) and a
friction factor correlation f (x)
• These correlations (h and f) were then used to
build a parametric model of the warmer
channels
Heat transfer and pressure drop in the warmer
channels were studied in details:
© 2010 ANSYS, Inc. All rights reserved. 31 ANSYS, Inc. Proprietary
yoomi - CFD Behind the Product
• Parametric space of the warmer design was explored in terms of the
channel width w and height h
• A number of contour maps of the pressure drop and the temperature
increase were produced to help determine the optimum channel design
a)
b)
h
[mm]
h
[mm]
w [mm] w [mm] a)
b)
h
[mm]
h
[mm]
w [mm] w [mm]
pressure
drop temperature
increase
© 2010 ANSYS, Inc. All rights reserved. 32 ANSYS, Inc. Proprietary
yoomi - CFD Behind the Product
• Text
The result of the design optimisation exercise
was a zig-zag channel of the specific width w
and height h
© 2010 ANSYS, Inc. All rights reserved. 33 ANSYS, Inc. Proprietary
yoomi - CFD Behind the Product
• milk temperature at steady
drinking speed
• sensitivity to the material
properties
• sensitivity to the milk flow rate
and thermal boundary conditions
10
15
20
25
30
35
40
45
50
55
0 100 200 300 400 500 600
time [s]
Tm
ilk
[C
]
Prototype 1
Prototype 3
Prototype 3, Al
Prototype 3, enh. k.
Prototype 3, Al and enh. k
These initial CFD simulations did
provide valuable information on the
warmer thermal characteristics:
but were significantly over-
predicting the milk first drop
temperature due to the single-
phase flow representation
© 2010 ANSYS, Inc. All rights reserved. 34 ANSYS, Inc. Proprietary
yoomi - CFD Behind the Product
An accurate prediction of the first drop
temperature and the pressure variations
inside the channel required
• multiphase CFD analysis
• modelling of conjugate heat transfer
through solid parts
• solidification reaction of the mixture
Using such multiphase CFD analysis, we were able to predict the first drop
temperature with accuracy of 2-3oC in comparison to the experimental
measurements
© 2010 ANSYS, Inc. All rights reserved. 35 ANSYS, Inc. Proprietary
yoomi - CFD Behind the Product
• Use of CFD simulation techniques saved a large amount of time and
development costs
• The product was developed in just 2.5 years and most of the time was spent
on the problems related to production, marketing and distribution
• Four physical prototype were ever built, only 2 of them to test thermo-hydraulic
performance of the bottle
• The simulation driven product development not only helped to meet the design
objectives, but also enable us to better understand the physical processes and,
therefore, to improve the performance of the product
For more information on this work and Intelligent Fluid Solutions,
please contact [email protected] or visit
www.intelligentfluidsolutions.co.uk
© 2010 ANSYS, Inc. All rights reserved. 36 ANSYS, Inc. Proprietary
Case Study – Waste Heat Recovery
• This example shows the use of ANSYS CFD to simulate the flow of
waste-heat exhaust gas to pre-heat water upstream of the water
being passed over the primary heat.
– ANSYS CFD used to calculate flow/conduction analysis to calculate
overall thermal performance and provide insight into fluid flow
– Set-Up
• Exhaust Gas - Air
• Flow Rate – 630 l/s
• Exhaust Gas Temp – 350 [C]
• Water Flow Rate – 15 [l/s]
• Water Temp – 15 [C]
• Tubes – Copper
• All Outside Boundaries
– HTC = 10 [W m^-2 K^-1]
– Outside Temp = 15 [C]
© 2010 ANSYS, Inc. All rights reserved. 37 ANSYS, Inc. Proprietary
Case Study – Waste Heat Recovery
• Geometry and CFD mesh
© 2010 ANSYS, Inc. All rights reserved. 38 ANSYS, Inc. Proprietary
Case Study – Waste Heat Recovery
• Results
Quantitative data
© 2010 ANSYS, Inc. All rights reserved. 39 ANSYS, Inc. Proprietary
Case Study – Waste Heat Recovery
• Results
Gas temperature• Results
Tube temperatures
© 2010 ANSYS, Inc. All rights reserved. 40 ANSYS, Inc. Proprietary
Case Study – Waste Heat Recovery
• Results
Gas temperatures and
velocity vectors
Definite scope for optimisation
© 2010 ANSYS, Inc. All rights reserved. 41 ANSYS, Inc. Proprietary
Case Study – Water jacket
• Bearings can produce a considerable
amount of heat during operation and
requires cooling.
• This example shows an ANSYS CFD
calculation on a water jacket to calculate the
temperature distribution in the metal work as
well as water flow.
– Concern about temperature distribution in
metalwork
– Set-Up
• Fluid – Water
– Flow Rate – 135 l/h
– Temp In – 5 [C]
• Solid - Aluminium
• Inside temperature – 150 [C] (Heat generated by the
bearing) Prescibed on inner wall of annulus
• Outside Boundary – Fully insulated
© 2010 ANSYS, Inc. All rights reserved. 42 ANSYS, Inc. Proprietary
Case Study – Water jacket
• Geometry of water
passage cut out of
solid bearing made of
aluminium
© 2010 ANSYS, Inc. All rights reserved. 43 ANSYS, Inc. Proprietary
Case Study – Water jacket
• CFD Mesh in water passage
• CFD Mesh in
jacket and
water passage
© 2010 ANSYS, Inc. All rights reserved. 44 ANSYS, Inc. Proprietary
Case Study – Water jacket
• Water streamlines coloured with
temperature on journey through water
passage
• Passage inside surface
temperatures
© 2010 ANSYS, Inc. All rights reserved. 45 ANSYS, Inc. Proprietary
Case Study – Water jacket
• Aluminium temperatures with water
passage visible• Aluminium temperatures
© 2010 ANSYS, Inc. All rights reserved. 46 ANSYS, Inc. Proprietary
Case Study – Plate Heat Exchanger
• Plate heat exchangers offer large surface areas for heat exchange.
Using the latest CFD meshing methods, it is now possible to rapidly
use ANSYS CFD to investigate the flow/conduction performance of
plate heat exchangers
• Set-Up
• Fluid - Water
• Flow Rate – 7.2 l/s
• Cold Temp In – 15 [C]
• Hot Temp In – 85 [C]
• Solid – Copper
• All Outside Boundaries – Fully Insulated
© 2010 ANSYS, Inc. All rights reserved. 47 ANSYS, Inc. Proprietary
Case Study – Plate Heat Exchanger
• Geometry
• Mesh
• Results
© 2010 ANSYS, Inc. All rights reserved. 48 ANSYS, Inc. Proprietary
Case Study – Electronics Thermal Management
• Mechanical engineers are often tasked with ensuring that the
electronic components within assemblies don’t overheat. This
example shows ANSYS CFD being used to calculate the flow of
coolant air and conduction in a typical scenario where the peak-
temperatures had to be kept below a certain temperature.
– Set-Up
• Cooling Fluid - Air
• Flow Rate – 1 m/s at Inlet
• Temp In – 20 [C]
• All Outside Boundaries
– Fully Insulated
• ICs heat source
– 1.5 Watts + 6.7 Watts
ICs
© 2010 ANSYS, Inc. All rights reserved. 49 ANSYS, Inc. Proprietary
Case Study – Electronics Thermal Management
• Geometry
Air enclosure
Single air inlet
Two outlets
• Mesh
• Results
Air and solid temperatures
Component temperatures
Structural displacementTemperatures transferred to
ANSYS Mechanical for
thermal stressing analysis
© 2010 ANSYS, Inc. All rights reserved. 50 ANSYS, Inc. Proprietary
Case Study – Exhaust System
• An excellent example of ANSYS CFD
and ANSYS Mechanical being used in
tandem is in exhaust system design
• Fluid mechanics
• Thermal and structural loads
• Fatigue
• Time dependent one-way transfer of
ANSYS CFD results to ANSYS
Mechanical at multiple instances
• Assumption that the displacement
of geometry due to thermal
stressing doesn’t have an impact on
the flow
• One-way transfer of metalwork
temperatures from CFD calculation
to ANSYS Mechanical
CFD
geometry
FE geometry
© 2010 ANSYS, Inc. All rights reserved. 51 ANSYS, Inc. Proprietary
Case Study – Exhaust System
ANSYS
CFD
© 2010 ANSYS, Inc. All rights reserved. 52 ANSYS, Inc. Proprietary
Deformations
Stresses
Case Study – Exhaust System
© 2010 ANSYS, Inc. All rights reserved. 53 ANSYS, Inc. Proprietary
Case study: Fire Simulation.
• We have a recently completed transient
two-way coupled ANSYS CFD and
ANSYS Mechanical example
• I-beam subjected to hot gases and
thermal radiation from a fire
• Weaken under thermal load
© 2010 ANSYS, Inc. All rights reserved. 54 ANSYS, Inc. Proprietary
Temperature Dependent Properties
• Structural Properties defined in Engineering Materials
– Property tables entered as functions of temperature
© 2010 ANSYS, Inc. All rights reserved. 55 ANSYS, Inc. Proprietary
Case study: Typical results.
© 2010 ANSYS, Inc. All rights reserved. 56 ANSYS, Inc. Proprietary
Software demonstration
• To showcase ANSYS CFD and ANSYS Mechanical, we’ve prepared a
software demonstration on a gas – liquid heat exchanger
– Attendees will see these tools through the ANSYS Workbench environment
• ANSYS CFD used to simulate flow and conduction
• We’ll show the workflow in performing an ANSYS CFD calculation
– Geometry (from CAD or ANSYS DesignModeler)
– CFD Meshing
– CFD Physics Set-up
– CFD Solving
– CFD Post-processing
• Then we’ll transfer the data to ANSYS Mechanical and calculate
– Thermal stressing ,deformation and fatigue
© 2010 ANSYS, Inc. All rights reserved. 57 ANSYS, Inc. Proprietary
Software demonstration
• Heat exchanger (gas/liquid)
• Confirm performance with CFD for 24
tube arrangement
• Assess performance with 16 tubes
using ANSYS CFD software
– Need gas temperature change >250 K
• Fluid Set-Up
• Water enters at 10C, 9 m3 per hour
• Hot gas enters at 933K, 0.4 kg/s, 10 bara
• Copper tubes
• Steel baffles and casing
• Flow results passed to structural
analysis to obtain structural response
under thermal load.
• Induced stress used to make fatigue
prediction and calculate factor of safety
Hot gas
© 2010 ANSYS, Inc. All rights reserved. 58 ANSYS, Inc. Proprietary
To software demonstration
• At the seminar, a live software demonstration
was performed
• This pdf contains slides to summarise the
demonstration
© 2010 ANSYS, Inc. All rights reserved. 59 ANSYS, Inc. Proprietary
Software demonstration
• Results – Streamlines of gas trajectories coloured by velocity
16 Tubes 24Tubes
© 2010 ANSYS, Inc. All rights reserved. 60 ANSYS, Inc. Proprietary
Software demonstration
• Results – Gas flow is more orderly when there are more tubes,
lower outlet gas temperature.
16 Tubes 24 Tubes
© 2010 ANSYS, Inc. All rights reserved. 61 ANSYS, Inc. Proprietary
Software demonstration
• Results – Improved temperature distribution with 24 tubes
16 Tubes 24 Tubes
© 2010 ANSYS, Inc. All rights reserved. 62 ANSYS, Inc. Proprietary
Software demonstration
• Results – Gas velocity on centre-plane more uniform with 24 tubes
16 Tubes 24Tubes
© 2010 ANSYS, Inc. All rights reserved. 63 ANSYS, Inc. Proprietary
Software demonstration
• Result – Gas temperatures in heat exchanger on centre-plane
16 Tubes 24 Tubes
© 2010 ANSYS, Inc. All rights reserved. 64 ANSYS, Inc. Proprietary
Software demonstration
• Quantitative Results from CFD simulations
– 16 tube configuration yields acceptable gas temperature reduction
16 Tubes 24 Tubes
Change in water
temperature [K]
6.3 K 7.7 K
Change in gas
temperature [K]
330.1 K 407.2 K
Change in water pressure
[Pa]
390 Pa 390 Pa
Change in gas pressure
[Pa]
1492 Pa 2159 Pa
© 2010 ANSYS, Inc. All rights reserved. 65 ANSYS, Inc. Proprietary
Structural problem definition
Boundary Conditions for a
symmetrical model
Temperatures applied
automatically
from CFD model
• ANSYS Mechanical software used to assess structural integrity of
16 tube design under thermal loading
© 2010 ANSYS, Inc. All rights reserved. 66 ANSYS, Inc. Proprietary
Response to thermal loadings
Contours of deformation
displayed on the
Deformed shape (exaggerated)
Equivalent Alternating Stress
in the component due to
thermal straining
© 2010 ANSYS, Inc. All rights reserved. 67 ANSYS, Inc. Proprietary
Fatigue Analysis
An S-N curve is applied in the
material properties.
Hence the part‟s life (repeats to
failure) can be calculated due to
the stress cycling
Contours of
Factor Of Safety
versus the specified
required design life
© 2010 ANSYS, Inc. All rights reserved. 68 ANSYS, Inc. Proprietary
Submodel for detailed analysis
To refine the results a
submodel may be
desireable with a locally refined mesh.
This delivers more accurate stress
results for the fatigue calculation.
© 2010 ANSYS, Inc. All rights reserved. 69 ANSYS, Inc. Proprietary
Heat exchanger summary
• ANSYS CFD software
used to assess
thermal/flow
performance of 24
and16 tube designs
• Acceptable
performance
achieved with 16
tube design
• ANSYS Mechanical
software used to
assess structural
integrity of 16 tube
design
• Life expectancy
and safety factor
quantified
© 2010 ANSYS, Inc. All rights reserved. 70 ANSYS, Inc. Proprietary
Today’s Agenda
14.00 – 14.05Introduction and WelcomeNigel Atkinson, ANSYS UK
14.05 – 14.20
Overview of the ANSYS Engineering Simulation Software Suite:
- ANSYS CFD to calculate flow distributions, pressure drops and conjugate heat transfer
including convection, conduction and thermal radiation
- ANSYS Mechanical to calculate both thermal stressing and structural fatigue
- The Workbench environment to facilitate integrated multidisciplinary simulationMark Leddin & Paul Everitt, ANSYS UK
14.20 – 14.30
Improving CFD Predictions of Heat Transfer
- Near-wall mesh refinement
- Advanced turbulence modelling methodsPaul Everitt, ANSYS UK,
14.30 – 15.15
Case Studies
- Heat exchangers and boilers
- Cooling jacket
- Radiators
- Waste heat recovery unit
- Thermal battery
- Electronics thermal management
- Other miscellaneous applicationsMark Leddin & Paul Everitt, ANSYS UK
15.15 – 15.30 Coffee Break
15.30 – 16.15Software Demonstration of Integrated Fluid Flow, Thermal Stressing and
Fatigue Analysis on Heat Exchanging DeviceMark Leddin & Paul Everitt, ANSYS UK
16.15 Summary and Q&A
© 2010 ANSYS, Inc. All rights reserved. 71 ANSYS, Inc. Proprietary
Invitation
There are many challenges facing mechanical engineers as they strive to
maximise the performance of heat exchanging equipment and to meet
more demanding thermal management objectives. Typical requirements
are to:
• Improve heat exchange
• Optimise cooling
• Reduce peak-temperatures
• Increase product efficiency
We hope that this seminar has introduced the unique capabilities of the
ANSYS product suite to perform integrated flow, thermal, stress and
fatigue analysis, giving mechanical engineers the simulation tools they
need to deliver better performing designs, in shortened development
times with reduced development costs.
• Reduce power consumption
• Ensure structural integrity
• Minimise material costs
• Reduce equipment dimensions
© 2010 ANSYS, Inc. All rights reserved. 72 ANSYS, Inc. Proprietary© 2010 ANSYS, Inc. All rights reserved. 72 ANSYS, Inc. Proprietary
Assessing & Optimising
Heat Transfer,
Structural Response
and Fatigue in
Mechanical Engineering
Product Design
Nigel Atkinson
ANSYS UK Ltd
Q&A