Additive Manufacturing of Compact Heat Exchangers - …hexag.org/news/34/ahmed_hussein.pdf · Ultrasonic shaker table –Varying frequencies are applied while the unit is contently

© HiETA Technologies Ltd 2016 - The information in this presentation contains confidential and/or privileged material. You are hereby notified that any disclosure, copying, distribution or use of the information contained herein or in any attachment is strictly prohibited.

Additive Manufacturing of Compact Heat Exchangers

Dr. Ahmed Hussein [email protected]

34TH HEXAG MEETING

20 June 2017

THE BUTTERY & L101, MERZ COURT, NEWCASTLE UNIVERSITY

mailto:[email protected]

© HiETA Technologies Ltd 2016

About HiETA

• Founded in 2011 with 25 employees.

• Based in Bristol and Bath Science Park (BBSP)

• Specialists in Thermal Management & Lightweight systems using Additive Manufacturing

• Thermal and energy Management:

• Ultra-compact heat exchangers: both single and two phase for microturbine, waste heat recovery unit, and electronics cooling.

• Waste Heat recovery systems

• Combustors & Injectors

• Turbo Machinery (turbine wheels for Temp. ~1000C)

• Lightweighting & topology Optimisation:

• Hybrid Truss structures

• Sporting goods

• High strength-to-weight ratio lattice structures

• Product design Services:

• Product design solution for both existing and new products using our expertise in Engineering analysis and Additive Manufacturing.


Product Portfolio

Customer requirements converted into innovative solutions using AM

Micro Power

Generation

Waste Heat

Recovery

Highly

Efficient ICE

Lightweighting and

Optimisation

Micro Gas Turbine Inverted brayton cycle

system

Plasma-assisted catalyst

support

Turbo machinery

Reciprocating engine

Cooled turbine

wheels (CM247)

Cooled

compressor

Hollow head

valveCooled exhaust

Lattice architecturesThrust nozzleTurbine nozzle

Hybrid Truss Structures

Novel composite-to-metal joints

Cuboid

Recuperator

Annular radial

Recuperator


HiETA AM value chain

HiETA is developing an integrated and validated value chain approach to deliver:

Maximum performance

Minimum volume and weight

Minimum cost

Quality assurance

Operations

Maintainence Overhall Repair


HX 1D sizing

LMTD, NTU methods

Multi-criteria optimisation

HX sizing, performance prediction

Correlation with analysis & test

Heat transfer surface selection

Correlation with test achieved

Niall

Harmonised 1-D sizing

tools (MathCAD,

SciLab)

HiETA AM value chain: Heat Exchanger


Novel HX core and manifold concepts

Performance enhancement of AM HXs are contributed to,

CAD design: The ability to make complex shapes and sizes that were difficult to make using conventional manufacturing techniques.

AM roughness: The inherent surface roughness and irregularities associated with the process allows flow separation and mixing at boundary layer. This effect is pronounced in channels with small hydraulic diameters.

Ability to optimise the core geometry size and shape of each fluid side of the HX for the best heat transfer and pressure drop.

Ability to make optimised complex manifold shapes that minimise the maldistributions in the HX.

Primary/secondary surfaces

HX coreFull HX with manifolds



Unit-cell CFD Optimisation

Altair Hypermesh

Altair AcuSolve

Correlation with 1-D

sizing & test

Altair Hypermorph

Altair Hyperstudy

OpenFOAM customised

solvers

© HiETA Technologies Ltd 2013 - www.hieta.biz - +44(0) 117 370 7733 - [email protected] - Bristol & Bath Science Park,Dirac Crescent, Emersons Green, Bristol, BS167FR

Hypermesh Acusolve AcuFieldView

Meshing/Preprocessing Solver Visualization

Optimization/DOE

Morphing

(HyperMorph)

HyperStudy

CFD Optimization

Design variables- shapes- parameters

Responses




Optimization/DOE

Morphing

(HyperMorph)

HyperStudy

CFD Optimization


Responses

Morphing Solver




Optimization/DOE

Morphing

(HyperMorph)

HyperStudy

CFD Optimization


Responses

Optimisation/design of

experiments




Optimization/DOE

Morphing

(HyperMorph)

HyperStudy

CFD Optimization


Responses

Complex flow i.e. 3D mixing,

multi-phase


Results

Friction factor (fF) Colburn factor (j)

Area goodness factor (j/f)

- Response surfaces plotted

versus corrugation ratio and

spacing ratio for fixed Re (200)

and aspect ratio (0.25)

Correlation with test achieved



Small-scale performance validation

CFD optimisationsCore performance analysis

Manifold optimisation (isothermal runs based on simplified porous core)

Experimental tests (single-phase and phase-change):

Single cell thermal and pressure tests

Applied heat flux or fixed wall temp.

Good insulation to minimise heat losses

Small component thermal and pressure tests

Dual fluid tests (air-to-air, water-to-water, air-to-water) - this is suitable for some of the geometries and provides more accurate result.

Boiling and condensation test rigs - In-house

Thermal performance test rig (single phase)

Core analysisManifold analysis

Performance correlations are used in 1D full HX sizing



HX Materials (Metals)

Material selection is a function of HX operating temperature, powder availability, and cost.

Nickel based alloys – INC625, INC718, CM247

Aluminium alloys – AlSi10, (6 series, 7 series, Scalmalloy).

Titanium alloys – Ti64

Steel alloys – 316 SS, 304 SS

Copper (purity ~ 99.9%) – Recent progress in various applications

Powder physical properties:Particle sphericity - (depends on the atomisation process) AM Powders are mostly spherical with some asymmetric particles and satellites present. A satellite is when a smaller particle sticks to a larger one during solidification.

Particle distribution - (10 - 60 µm - depends on material) – maximum size defines the minimum feature achievable and removability of the un-used powder)

Flowability - Methods such as Atomic layer deposition (ALD) are found to enhance flowability of some materials. Example, coating Nano-layer copper on Aluminium is currently developed in a collaborative project (IUK FLAC) with the Univ. of Liverpool.

Material property tests: Yield, tensile, and fatigue strength – usually small test coupons are tested at elevated temp. ranges for both as built and heat treated stage.

Creep strength

Thermal conductivity – affected by the microstructure changes in post-processing heat treatment stages – few studies conducted show improvement after heat treatment.



AM Process

Once the detailed CAD is ready, the next step is machine file preparation

Large HX units could take time to slice into 30-60 µm layers Small layer thickness produces finer quality but increases build time and cost

Slicing time is a function of the HX cross-sectional data

Main HX core may consist of many internal fins > 10,000 - huge data to process.

Its necessary to develop optimised set of process parameters for specific material and wall thickness

Key parameters include laser power, laser speed, hatch distance, contour or no contour etc.

Laser energy density is considered a key factor that affects the properties of as-built parts fabricated by AM process,

𝑬 =𝑷

𝒗.𝒉. 𝜹

𝑱

𝒎𝒎𝟑

𝑃- laser power, 𝑣 – laser speed, h – hatch spacing, 𝛿 – layer thickness

Production oriented machines are now being developed,Higher productivity – increased built rate

Automatic on-board powder sieving system

Higher laser powers and multiple lasers (~ 4 lasers working simultaneously)

Advanced monitoring systems

AM processing - SLM


HX unit manufactured and still attached to base-plate


Post-processing steps

Powder removalCan take few minutes or days depending on the complexity and hole size of the internal geometry.

Ultrasonic shaker table – Varying frequencies are applied while the unit is contently rotated. This is found to be very effective way of removing loose powder.

Air blowing

Stress relieving heat treatment This step is crucial due to high residual stresses present in the part from the process rapid melting and solidification.

Parts are place in furnace at ~ 30-50% of melting temperature of the material for 2-3 hours

Removing the part from base-plate Can be manual or Wire_EDM

Parts with large foot-print (HXs) usually need to be wire-EDM’ed

Leak testingPressurise one side of the HX

If the HX leaks, measure the leak-rate.

Some materials are solution heat-treated or aged to improve mechanical strength No specific heat-treatment guidelines exist for AM parts

Relies on the casting cycles which sometimes prove to be unsuitable for AM parts.

Hot isostatic pressing (Hipping) Effective in closing internal porosity of some parts while in others its found to be ineffective

Sometimes difficult to get uniform pressure across parts where internal channels exit.



QA : Non-destructive testing

There are always key AM HX challenges that require the used of a number of techniques,

Is the powder fully removed from the HX? Uncertainty in complex cores with tiny channels > 10,000.

Require sufficient time allocated for powder removal

Is there internal/external defect/s in the HX that will cause leakage or structural failure?

The dimensional accuracy of the core geometry?

CT analysis: is an expensive procedure and only used in understanding complex new concepts

Beneficial in revealing the pore size, wall thickness, and mainly part defects.

Difficult to get high resolution in large HX components

Acceptable defects in bulk parts can be treated as failure in thin wall HX components.

Knowing the defect location may facilitate the inspection on whether the defect is

AM Process or post-processing stages

CAD related

Optical Microscopy:

Used to check the dimensional accuracy

Can be used for defect inspection of polished surfaces

CT image Re-construction

Microscope image of thin walls



© HiETA Technologies Ltd 2015 - The information in this presentation contains confidential and/or privileged material. You are hereby notified that any disclosure, copying, distribution or use of the information contained herein or in any attachments is strictly prohibited.

Initial external camera setup

Nikon D200 camera placed in front of view window

Captures live images of the key process points

During AM powder deposition and laser scanning

Arduino monitoring AM machine parameters

Software work-flow developed for video creation

Identification of build failure modes


On-going machine mounted camera system


Surface roughness analysisOptical measurements completed by

Orientation = 90 degree Ra = 15.82 µm (Z-axis)Sa = 20.15 µm

Orientation = 45 degree Ra = 32 µm (Z-axis)Sa = 43.22 µm

• Inherent anisotropic surface roughness

in AM:

• X-Y, Z dependency

• Build orientation angle

• Geometric dependency

• Due to post-processing

• Topographic differences may exit even

after

• Post-processing technique (Shot peening,

laser polishing etc)

• Single Ra value will give an ambiguous

or incomplete description of the real

surface.

• Recommended the combined use of several surface texture parameters (Ra, Sa, Rz, Sz, skewness (Rsk or Ssk), kurtosis (Rku or Sku) etc) for full AM surface characterisation

• Requires understanding of surface parameters which are functionally relevant.

Ra = 8.35 µm (1000 lines) Ra = 5.28 µm (1000 lines)

AM

Bu

ild d

irec

tio

n

Visible layer boundaries



Full-scale performance testing

Determine if the HX meets the design specificationEffectiveness, Pressure drop

Sometimes apply thermal shock cycles

Characterise the unit performance in terms of pressure drop and heat transfer rate

Across a range of mass flowrates and temperatures

Validate the 1D sizing tool


HX performance testing @ Bath universityTemp. ~ 750C


AM Potential for volume and weight reduction

4L vs 15LAutomotiveAluminium

8L vs 54LEnergyInconel 625

7L vs 51LAutomotiveInconel 625


Unique position in terms of volume/weight reduction and lead time.

Rapid technology advancement in build-rate and material cost will allow to bring the cost down

Comparison of size reduction with customer conventional units:


Additive Manufacturing for Future Powertrains

Innovation & integration are key to unlock cost & efficiency potential –change of mindset required!

AM industry moving towards production

AM cuboid recuperatorSmaller size vs conventional

manufacturing method

Annular form recuperator

Decreased system package size

“Combustorator”Cost reduction, efficiency gain,

package reduction

Fully integrated turbine housing, combustor,

recuperatorLow cost, low space,

high efficiency


Delta Motorsport's range extended electric car at the LCV2016 event, 14 September 2016.

https://www.gov.uk/government/news/delta-motorsport-reveals-new-low-cost-micro-turbine-technology

HiETA are working with Delta Motorsport to develop a low cost, lightweight, small range extender (RE) for electric vehicles (EVs).

Recuperator spec.Effectiveness = 82%

Volume = 3 L

Mass = 7 Kg

Operating temp. =750C

Material = INC625

The tested Recuperator unit is 33% smaller in volume and 9.4% more effective against the conventional competition for the same spec.

Application: Range-Extender Microturbine Compact Recuperator


https://www.gov.uk/government/news/delta-motorsport-reveals-new-low-cost-micro-turbine-technology


Developed in collaboration with Axes Design and Bath univ. under iUK Project – Ibranch

Works on the principle of inverted Brayton cycle

System successfully bench tested.

Generates ~2K(basic system) and ~12KW (with condensation and steam generation/expansion)

HiETA developed compact condenser and boiler units (see Fig.)

Interest from JLR, Nissan and Isuzu.

Application: Exhaust energy recovery system (2L Petrol engine)


POST TURBINE HOT GAS

BOILER

CONDENSING HEAT

EXCHANGER

CONDENSATE SEPARATOR

WATER SUPPLY AND DRAIN

Bench test of the inverted Brayton cycle system with condenser and boiler units.

System overall weight = 9 kg


Thank you

Any Questions!

Documents

Additive Manufacturing of Compact Heat Exchangers - …hexag.org/news/34/ahmed_hussein.pdf · Ultrasonic shaker table –Varying frequencies are applied while the unit is contently