Embed Size (px)
Citation preview
SHOTEAM: Superalloy Heat Exchangers Optimized for
Temperature Extremes and Advanced Manufacturability
PI: Timothy Fisher, UCLA
We are solving a series of coupled optimization problems involving metal heat exchanger
materials, manufacturing, heat transfer, and reliability for new high-efficiency advanced
recuperated power cycles targeting aviation applications
Project Vision
Brief Project Overview
Context/history of the project
The UCLA PI and Honeywell Aerospace have a long history of collaboration, principally through
the Center for Integrated Thermal Management of Aerospace Vehicles (CITMAV). They have
worked on heat exchanger design for high-power opto-electronics and a variety of unsteady
thermal systems applications.
Fed. funding: $2.52M
Length 36 mo.
Team member Location Role in project
UCLA Los Angeles, CA Thermo-mechanical optimization, additive manufacturing
Honeywell Aerospace Torrance, CA Heat exchanger design and fabrication, T2M
University of Miami Miami, FL Creep and fatigue modeling
1
Outline
Task 2. Preliminary Heat Exchanger Design
Task 3. Preliminary Manufacturing Feasibility and Sub-scale Testing
Task 4. Thermomechanical Behavior
Task 5. Fabrication and Prototype
Task 6. Technology to Market
Summary
2
Task 2. Preliminary Heat Exchanger (HX) Design
3
Design Flow Path
4
Requirements
HX Effectiveness > 0.8
Internal Pressure Drop < 5 bar
Extremal Pressure Drop < 1.6 bar
Constraints
Optimization by
searching 50,000+
designs
Performance Requirements
Thermomechanics
Manufacturing Technologies Optimization Function
OF = Recurring Cost + Non-Recurrent
Cost + A x Weight + B x Volume + C X
Specific Fuel Consumption + D X MTBF
Optimization Model Optimal Design
CFD Models Sub-scale Tests
Refined
Correlations
Performance Model
Validation
Front View
Top View
Performance Model for Shell and Tube Heat Exchanger (STHX)
5
▸ Objective– Determine the thermal and hydrodynamic
performance of STHXs with high accuracy
and low computational time
▸Methodology– Use volume averaging to abstract the ‘unit
cell’ geometry in STHX
– Serially link the ‘unit cells’ to predict system
performance
– Develop correlations to estimate Colburn and
friction factors for external flow over tube
banks
– Apply established correction factors to
quantify the pressure and heat transfer losses
due to entrance, exit, turning and bypass
effects
Unit Cell
Optimization using Particle Swarm Optimization (PSO)
6
▸ Objective function: minimization of HX core
weight or HX cost
– HX core weight = mheader + mshell + mtubes + mbaffles
– HX cost = function of weight and manufacturability of
components
▸ Constraints
– Power = 50 kWth (Effectiveness, 𝜀 ≈ 0.81)
– Internal pressure drop, Δ𝑃𝑖 < 5 bar
– External pressure drop, Δ𝑃𝑜 < 1.6 bar
▸ Operating conditions
External Flow
(800 oC, 80 Bar)
External fluid Internal fluid
Inlet temperature [oC] 800 300
Inlet pressure [bar] 80 250
Mass flow rate [kg/s] 0.103 0.103
Example Optimization Study
Front view of HX Cross-section
‣ FLUENT model for ideal flow over
tube bundle
– Objective: predict turbulent forced convection
over tube bundle with bare and finned tubes
– SST 𝑘−𝜔 model in ANSYS FLUENT 20.2
– Fluid type: CO2 (from NIST1 database)
CFD Models for Heat Transfer and Hydraulic Performance
7
Velocity Inlet𝑢𝑖 , 𝑇𝑖 = 550℃
Outlet𝑇𝑜, 𝑃𝐺,𝑜 = 0
Inner Wall 𝑇𝑤𝑖
= 20℃
mesh
Symmetric walls
‣ FLUENT model for flow bypass and
maldistribution
– Objective: quantify effects of flow non-idealities
(bypass and maldistribution) in real STHX geometries
Shell-side (SS) Inlet
𝑚 = 0.1026𝑘𝑔
𝑠𝑇𝑠𝑠,𝑖𝑛 = 800℃
𝑃𝑠𝑠,𝑖𝑛 = 80 𝑏𝑎𝑟
Shell-side Outlet
𝑚 = 0.1026𝑘𝑔
𝑠
Tube-side Outlet
𝑚 = 0.1026𝑘𝑔
𝑠
Tube-side (TS) Inlet
𝑚 = 0.1026𝑘𝑔
𝑠𝑇𝑡𝑠,𝑖𝑛 = 550℃
𝑃𝑡𝑠,𝑖𝑛 = 250 𝑏𝑎𝑟
Adiabatic Walls
Velocity and temperature fields obtained
for representative geometries
Results for bare tube bundle match
the developed correlations in the
performance model
Task 3. Manufacturing Feasibility and Sub-scale Testing
8
Left top: disc fins
Left bottom: cylindrical pin fins
Right: helical fins
Prototypes measure 2” in length and 3 mm in OD
Prices are for prototype fabrication on Haynes
Feature Price
Disc fin $390
Pin fin $1176
Helical pin fin $1165
‣ Fabrication of augmented tubes
Prototype tube quotations: 2’’ long, 3 mm OD augmented
tubes ($390/tube) cost over 3 times higher than 24’’ long,
1 mm OD bare tubes ($125/tube) or
> 30 times higher cost/tube length
Sub-scale Tube Bundle Testing
‣ Objective: measure turbulent forced convection in a HX unit cell and obtain heat transfer
coefficient and friction factor data for correlation development and validation
‣ Fabricate test rigs with a bare and finned tube bundle in one ‘unit cell’
9
Air Heater
Air Exhaust
𝑇 = 100℃
𝑚
𝑃
𝑃
Compressed Air
𝑚
𝑃
𝑇 = 20℃
Tube Bundle Test
Section
𝑃
TCs
TCs
TCs Air Exhaust
Internal flow (Cold Air)Instrumentation
tubes
Fig. 3D Schematic of Tube Bundle Test Section
External flow (Hot Air)
Fig. 2D Schematic of Whole Test Rig
Fig. Picture of Whole Test Rig
We have fabricated the system and multiple tests are being conducted
Air Heater
Heater Controller
Air Supply Internal Inlet
External Flow Meter Tube Bundle Test Section Cooling HX
Data Acquisition System PC with LabVIEW
Data Preprocessing
Internal Flow Meter
External Inlet
External Outlet
ThermocouplesPressure Gauges
Sub-scale HX Test
‣ Objective: Obtain HX performance data to quantify flow maldistribution and validate our CFD and
performance models
‣ Fabricate a HX protype with multiple ‘unit cells’
10
Water
@20 oC
7.HX Test
Section
6.Cooling
HX01
4.CO2 Heater3.CO2
Compressor
1.CO2 Cylinder
Water
Return
𝑻 = 𝟐𝟎𝟎℃
𝑇 = 20℃
𝒎𝒎𝒂𝒙 = 𝟏. 𝟓 kg/min𝑷 = 𝟏𝟎𝟎 𝐛𝐚𝐫
CO2 Exhaust
2.Relief Valve
8.Air Heater
Compressed Air
𝑚𝑚𝑎𝑥~3.6 kg/min𝑃𝑚𝑎𝑥~5 bar
Air Exhaust
𝑇 = 300 ℃
5. Recuperator
Water@
20 oC
9.Cooling
HX 02
Water
Return
𝑃
𝑃
𝑚
𝑃
𝑃
𝑃
𝑃
𝑚
Internal flow
(sCO2@200℃and 100 bar)
Will have 39 3mm-OD tubes (13
tube rows and 6 tube columns)
Will have sealing strips to
eliminate bypass effect
External flow
(Hot Air @300℃and 5 bar)
Fig. 2D Schematic of Whole Test Rig
Fig. 3D Schematic of HX Test Section
We have designed the system and are currently fabricating CO2 loop
(with Accudyne System) and test section (with UCLA Machine Shop)
Task 4. Thermomechanical Behavior
11
‣ Linear thermomechanical model in ANSYS FLUENT
‣ Pressure and thermal loading
– Single header optimized to contain pressure but flexible to mitigate
thermal strain
– U-tube design eliminates tube buckling issue due to combined pressure
and transient thermal loading
‣ Creep
– Header flexibility and temperature gradient provides long creep life
– Microtube design has flexibility between the header and baffle during
steady state
‣ Thermal Low Cycle Fatigue (LCF)
– U-tube design provides flexibility during transient operation to enhance
LCF life
– Microtube design has flexibility between the header and baffle during
transient operation
– Header has long useful LCF life
Non-linear Microstructure-based Creep Model for Haynes 282
12
Climb: 𝐿𝑜𝑔𝜀𝑜𝐾𝑇
𝐷𝐿𝐺𝑏= 𝑎𝑐𝑙𝑖𝑚𝑏 𝐿𝑜𝑔
𝜎−𝜎𝑡ℎ
𝐺+ 𝑏𝑐𝑙𝑖𝑚𝑏
Nabarro-Herring: 𝐿𝑜𝑔𝜀𝑜𝐾𝑇
𝐷𝐿𝐺𝑏= 𝑎𝑁𝑎𝑏𝑎𝑟𝑟 𝐿𝑜𝑔
𝜎
𝐺+ 𝑏𝑁𝑎𝑏𝑎𝑟𝑟𝑜
elastic
Plastic (dislocation glide)
Creep (dislocation climb)Diffusion creep (Nabarro-Herring)
Raw data for secondary creep rates
Secondary creep rate fit to dislocation climb and diffusion creep
Dislocation-diffusion continuum creep model
Micro-mechanics of dislocation glide & interaction with precipitates
Task 5. Fabrication and Prototype
13
Fabrication and Assembly Process is Similar to Those Employed by Honeywell for Numerous Aerospace Tubular HXs
Configuration
Overall Configuration
Established
• Shell and tube HX
• “U” bent micro tubes
Fabrication Plan
Detail Parts and
Assembly Plan Well
Understood
• All detail parts to be procured
• Machined or 3D printed
headers and baffles
• Core stacked and brazed at
Honeywell
• Outer HX assembly to be
welded at Honeywell
Key Detail Parts
Samples of Key Detail
Parts Obtained
• Different radius tubes
fabricated
• Headers printed
Go-Forward Plan
Develop Critical Special
Process
• Brazing
• Heat treatment
Identify Suppliers
• Machined details
• 3D printed details
• Obtain quotes
Refine Hdw Estimates
• Quotes from suppliers
• Supply chain and
assembly
Braze Trials for Header Joining
14
Tube
material
Header
material
Tube thickness
(OD, in.)# of tubes
Braze
metal
Braze temp.
(°F)
Haynes 282 AM Haynes 282 0.04020 AMS 4778
198520 AMS 4777
Haynes 282 tubes
Evaluation of braze trials
• Quality of fillets and indications of wetting
• Evidence of flow – full penetration
• Indications of erosion
Methods
• Visual inspection
• Cross-section observation
• Microscopy
• Metallography
• Photo documentation
Lessons learned from preliminary CRES 304 trial
• Good wetting of braze metal and tubes
• Tube tolerance variation
• Potential need for additional braze cycles
• Length of tube protrusion
• Potential solutions for plugging tubes during stacking
Current Investigation
Alternative Joining Methods
15
Laser welding is also being studied for potential tube-to-header joining
Increasing weld depth more difficult as number of tubes increases and tube spacing decreases
Transient Liquid Phase (TLP) bonding can produce sound joints, as shown in figure1 and experimental micrograph
1. Paulonis, D. F.; Duvall, D. S.; Owczarski, W. A. Diffusion Bonding Utilizing Transient Liquid Phase, 1972.
Optical images of preliminary TLP bonding experiments
Cross section of a 1/16”-thick Haynes 282 sheet with
different laser welding speed (scale bar is 1 mm)
Task 6. Technology to Market
16
• Identified product application for Aerospace marketplace
- Aircraft gas turbines produce thrust for aircraft and must be fuel efficient
- Thrust is produced by burning fuel and expanding it through high temperature turbines
- The turbines must be actively cooled with air
- For next generation engines, a cooling air heat exchanger will extend turbine blade life
• Established a working set of requirements for the future cooling air heat exchanger
- Design will be scaled from 50kW of present program to enable
T2M development (heat exchanger will be much larger)
• Evaluated potential market for cooling air heat exchangers
based on current trends
- Aerospace turbine engine market is estimated to exceed $90
Billion within ten years
- A segment of the market will require cooling air heat exchangers
Typical Aircraft Gas Turbine
Like
liho
od
Almost Certain
Likely
Moderate
Unlikely
Rare
Insignificant Minor Moderate Major Catastrophic
Consequences
Risk Update
Risk
1. Material incompatibility between
metal and fluid components at/near
operating conditions
2. Material reliability compromised
at/near operating conditions
3. Modest/no enhancement from
topologically optimized inserts within
manufacturing constraints
4. New header joining methods under
development
5. Excessive projected cost of
manufacturing for commercial-scale HX
43
21
X
X
Now
Start of project
17
5
3
1 2
45
Progress Against Tasks – Timetable
‣ Remaining work (high level)
– Preliminary design and manufacturing reviews for 50 kWth HX
– Complete sub-scale tests
– Critical design review for 50 kWth HX
– Gen 2 500 kWth conceptual design
‣ Main challenges
– Development of predictive models for creep-fatigue behavior under extreme conditions
– Integration of potential new manufacturing processes to improve industry standard practice
– Inclusion of realistic/practical margin factors on total thermohydraulic performance
18
Task Name Start End Status
Task 1 Refine tasks and milestones for the work plan 9/29/2019 12/29/2019
Task 2Heat exchanger design and optimization
Current status: preliminary design of 50 kWth completed9/29/2019 9/29/2022
Task 3Preliminary manufacturing feasibility and sub-scale testing
Current status: fabricating the second test rig9/29/2019 12/29/2020
Task 4Thermomechanical model
Current status:12/29/2019 9/29/2021
Task 5Fabrication and Prototype
Current status:3/29/2020 6/29/2022
Task 6Technology to Market
Current status:6/29/2020 9/29/2022
Task Name Start End Status
Task 1 Refine tasks and milestones for the work plan 9/29/2019 12/29/2019
Task 2
Preliminary heat exchanger design and optimization
Current status: preliminary design of 50 kWth completed by
12/29/20
9/29/2019 12/29/2020
Task 3Manufacturing feasibility and sub-scale testing
Current status: fabricating the second test rig9/29/2019 12/29/2020
Task 4
Thermomechanical model
Current status: connecting creep-fatigue industry models with
deeper theory
12/29/2019 9/29/2021
Task 5Fabrication and prototype
Current status: deep analysis of all materials and processes3/29/2020 6/29/2022
Task 6Technology to market
Current status: evaluating air HX market for similar conditions6/29/2020 9/29/2022
Potential Partnerships
‣ Resources and expertise needed
– Efficient sub-scale prototyping
– Scaling up of new joining processes
– Long-term thermomechanical testing resources
‣ Anticipated needs following the completion of the award
– Support for development of 10x larger heat exchanger beyond conceptual design
‣ What do we need to successfully commercialize the technology?
– Intermediate air-air HX applications
– Integration with sCO2 aviation platforms as they emerge
19
