Heat Transfer, and Fatigue in Product Design UK/staticassets... · Response and Fatigue in...

© 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


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


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


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


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


Workbench

• Workbench is a project environment that

offers process chaining, management and

scripting


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


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


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


Today’s Agenda


14.05 – 14.20

Overview of the ANSYS Engineering Simulation Software Suite:

- ANSYS CFD to calculate flow distributions, pressure drops and conjugate heat transfer



- 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


- Thermal battery


- Other miscellaneous applicationsMark Leddin & Paul Everitt, ANSYS UK


15.30 – 16.15Software Demonstration of Integrated Fluid Flow, Thermal Stressing and

Fatigue Analysis on Heat Exchanging DeviceMark Leddin & Paul Everitt, ANSYS UK



Assessing and

Optimising Heat

Transfer, Structural

Response and Fatigue

in Mechanical

Engineering Product

Design

14th

June 2011

Paul Everitt

Mark Leddin

ANSYS UK Ltd


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


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


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


• 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




• 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




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


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.


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]



• 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



• Solid temperatures passed to ANSYS Mechanical and

FE analysis performed to calculate deformation and

stress

Thermal stressDeformation


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.


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


yoomi

CFD Behind the Product

Dr. Andrej Horvat

Intelligent Fluid Solutions Ltd.


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.

http://www.yoomi.com/







• 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.



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:



• 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



• Text

The result of the design optimisation exercise

was a zig-zag channel of the specific width w

and height h



• 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



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



• 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

mailto:[email protected]

http://www.intelligentfluidsolutions.co.uk/


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]



• Geometry and CFD mesh



• Results

Quantitative data



• Results

Gas temperature• Results

Tube temperatures



• Results

Gas temperatures and

velocity vectors

Definite scope for optimisation


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



• Geometry of water

passage cut out of

solid bearing made of

aluminium



• CFD Mesh in water passage

• CFD Mesh in

jacket and

water passage



• Water streamlines coloured with

temperature on journey through water

passage

• Passage inside surface

temperatures



• Aluminium temperatures with water

passage visible• Aluminium temperatures


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


Case Study – Plate Heat Exchanger

• Geometry

• Mesh

• Results


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


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


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



ANSYS

CFD


Deformations

Stresses



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


Temperature Dependent Properties

• Structural Properties defined in Engineering Materials

– Property tables entered as functions of temperature


Case study: Typical results.


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



• 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


To software demonstration

• At the seminar, a live software demonstration

was performed

• This pdf contains slides to summarise the

demonstration



• Results – Streamlines of gas trajectories coloured by velocity

16 Tubes 24Tubes



• Results – Gas flow is more orderly when there are more tubes,

lower outlet gas temperature.

16 Tubes 24 Tubes



• Results – Improved temperature distribution with 24 tubes

16 Tubes 24 Tubes



• Results – Gas velocity on centre-plane more uniform with 24 tubes

16 Tubes 24Tubes



• Result – Gas temperatures in heat exchanger on centre-plane

16 Tubes 24 Tubes



• 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


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


Response to thermal loadings

Contours of deformation

displayed on the

Deformed shape (exaggerated)

Equivalent Alternating Stress

in the component due to

thermal straining


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


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.


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


Today’s Agenda


14.05 – 14.20

Overview of the ANSYS Engineering Simulation Software Suite:

- ANSYS CFD to calculate flow distributions, pressure drops and conjugate heat transfer



- 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


- Thermal battery


- Other miscellaneous applicationsMark Leddin & Paul Everitt, ANSYS UK


15.30 – 16.15Software Demonstration of Integrated Fluid Flow, Thermal Stressing and

Fatigue Analysis on Heat Exchanging DeviceMark Leddin & Paul Everitt, ANSYS UK



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


Assessing & Optimising

Heat Transfer,

Structural Response

and Fatigue in

Mechanical Engineering

Product Design

Nigel Atkinson

ANSYS UK Ltd

Q&A

Date post:	06-Feb-2018
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Heat Transfer, and Fatigue in Product Design UK/staticassets... · Response and Fatigue in...

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