The Use of Finite Element Modeling in Thermal Packaging Design

www.cryopak.comwww.tcpreliablegroup.com

Presented By:Landon HalloranFinite Element Analysis [email protected] 2011

The Use of Finite Element Modeling in Thermal Packaging Design


Overview• Advantages of Thermal Modeling in the Design

Process • Introduction to Finite Element Analysis• Heat Transfer• Thermal Simulation• Simulation of Standard Designs• Simulation as Part of the Development

Process: Case Studies

2L. Halloran 12/Oct/2011


Advantages of Including Thermal Modeling in the Design Process



Why Simulate?• No prototyping required• No inventory required• Saves on chamber time• Limitless number of temperature probes• Can identify susceptible locations in the pack-out• Accelerates the design process• Multiple variations can be tested and compared• Graphic rendering for customers



Introduction to Finite Element Analysis



A Wide Variety of Applications



What is “Finite Element Analysis”?• A computational method for performing analysis

of a physical system.• A tool for simulation of the mechanical, thermal,

rheological, electronic or other response of a system.

• Involves the division of a body into smaller domains or “elements”.

• The applicable equations describing the physics of the system can then be evaluated for each of the elements.



A Simple Example in 2-D: I

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An odd-shaped sheet of HDPE is subjected to a heat input and output, as

well as constant temperatures at two places.

40°C

10°C

-10 W/m2

A CAD model of the sheet is divided into smaller components by meshing.

10 W/m2

L. Halloran 12/Oct/2011


A Simple Example in 2-D: II

40°C

10°C

-10 W/m2

Constraints such as fixed temperatures are defined in the simulation set-up.

The simulation algorithm runs with multiple iterations and calculates the resulting temperature throughout the

object.

10 W/m2



Heat Transfer



Heat Transfer: I• There are three methods of heat transfer between

two objects:– Conduction

• Transfer of thermal energy through direct contact• Fourier’s Law: q = kAΔT/Δx

– Convection• Transfer of thermal energy through a fluid• Can be free or forced• q = hcAΔT

– Radiation• Transfer of energy through electromagnetic radiation emitted by all objects

with temperature > 0°K (-273°C) • Hotter objects emit more power: P = σT4



Heat Transfer: II• In thermal packaging, the primary method of

heat transfer is conduction• Free convection by air cells in a packaging

configuration also have a significant effect• To properly treat both mechanisms of heat

transfer, a hybrid thermal-fluid solver is required



Thermal Simulation



Thermal Simulation: I• In order for thermal simulation to be an

integral part of the design process, simulation results must be validated.

• In thermal/flow simulation, there are multiple user parameters and options that govern the thermodynamics of the modelled system.

• Many of these can be measured directly, however many must be determined through simulated experiment



Thermal Simulation: II• Finding the correct simulation parameters and

making the appropriate geometric approximations present the biggest challenges in obtaining simulation results that accurately replicate test results.

• A standard set of processes, options and parameters has been developed leading to acceptable simulation results for existing and new thermal packaging designs.



Models of Individual Components

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• Database of part drawings • Can be used as

components in assembly models and simulations.

• Geometry is generally simplified for simulation


Simulation Parameters and Options

• Density, specific heat capacity, and thermal conductivity

• Convective heat transfer multiplier• Radiative and convective thermal coupling to ambient

environment• Conductive contact between tangent faces• Solver parameters• Others



Parameterization Simulation

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0 12 24 36 482

3

4

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9

10

11

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Effect of Convective Heat Transfer Multiplier (TS-48 Large Canadian with ATP Summer 48H Profile)

Test - Probe 7Test - Probe 10Simulation - CHTM=1Simulation - CHTM=0.5Simulation - CHTM=0.25Simulation - CHTM=0.125

Time (h)

Tem

pera

ture

(C)

The extent to which the convective heat transfer multiplier affects results can be readily seen here.



Materials: I• For valid simulation results, accurate values of several

physical properties of each material are required:– Density (ρ)– Specific heat capacity (cp)– Thermal conductivity (k)

• For PCMs, values for these properties are required both above and below the phase-change temperature, as well as:– Latent heat capacity (L)– Phase change temperature (TPC)

• Some of these material properties exhibit a significant variation over the temperature range of interest and must be programmed as temperature-dependent tables.



Materials: II• PCMs

– Water-based Cryogels– Phase-5– Phase-22– Phase-27– 20-Below Gel– Dry Ice

• Containers – Corrugated Cardboard– HDPE/LDPE

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• Insulators– Expanded Polystyrene

(EPS)– Low, medium and high

density– Polyurethane (PUR)– Polyisocyanurate (PIR)– Vacuum Insulated Panels

• Others



Simulation of Standard Designs



Simulations of Standard Designs• TimeSaver 24 Small (US)• TimeSaver 48 Premium Medium (US)• TimeSaver 48 Large (Canada)• TimeSaver 96 PUR Small (US)



TimeSaver-24 Small



Design Details

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• 12 CG1181 gel packs.• Was simulated both with and

without a convective heat transfer coefficient multiplier to effectively model the configuration with and without bubble wrap.

• Gel packs were modeled with a simplified geometry and with an averaged conductive heat transfer coefficient.



Summer Simulation Results

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“w/ bubble-wrap” “w/o bubble-wrap”

0 6 12 18 240

5

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20

25

30

35

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Test #1 Test #2 Test #3Solution 1 SIM (with HTCM=1/8) Solution 3 SIM ISTA Summer 24H

Time (h)

Tem

pera

ture

(°C)



Winter Simulation Results

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0 6 12 18 24

-15

-10

-5

0

5

10

15

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Test #1 Test #2 Test #3Solution 2 SIM (with HTCM=1/8) Solution 4 SIM ISTA Winter 24H

Time (h)

Tem

pera

ture

(°C)

“w/ bubble-wrap” “w/o bubble-wrap”



TimeSaver-48 Medium Premium



Model Details

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• Presence of two different PCMs, Phase-5 and water-based gels, presents additional challenges in obtaining accurate simulation results.

• To account for attenuated convective heat transfer due to blockage from bubble-wrap , a convective heat transfer coefficient multiplier was used.

• Conduction assumed perfect between EPS layers

• Effective conductive transfer coefficient used for other surface-to-surface contact

Cut-away view of 48H Winter Simulation



Simulation Results - Winter

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0.61°C

0 12 24 36 48

-15

-10

-5

0

5

10

15

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TimeSaver 48 Medium Premium - Winter Minimum Load

Qualification Test #1 Qualification Test #2 Qualification Test #3Simulation Payload T ISTA Winter 48H

Time (h)

Tem

pera

ture

(C)



TimeSaver-48 Large Canadian



Model Details

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• Customer expressed interest in using the design but as concerned about the performance against their own temperature profile.

• In order to facilitate the conversation the shipper was modeled and tested against the profile in question.

• Gel packs are the sole PCMs. Modeled geometry was idealized.

• Effective conductive heat transfer coefficient used

• Effect of convective heat transfer multiplier was extensively investigated with this model.

Final Temperature - Winter

Final Temperature - Summer



Simulation Results - Summer

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0 12 24 36 480

5

10

15

20

25

30

35

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Timesaver-48 Large Canadian Assembly 001 – Summer – SIM 001: Solution 10 - ATP Canadian Summer 48H

Payload Test TemperaturePayload Simulation TemperatureTemperature Profile

Time (h)

Tem

pera

ture

(C)




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0 6 12 18 24 30 36 42 48

-25

-20

-15

-10

-5

0

5

10

15

20

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Timesaver-48 Large Canadian Assembly 001 - SIM 001: Solution 2 - ATP Canadian Winter 48H

Temp Probe 1 (C) Temp Probe 2 (C) Payload Simulation (C) External Profile Temperature

Time (h)

Tem

pera

ture

(C)



Simulation Results – Winter (Customer-supplied profile)

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0 12 24 36 480

1

2

3

4

5

6

7

8

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Timesaver-48 Large Canadian Assembly 001 - SIM 001: Solution 3 - Lynden Winter 51H

External Temperature Profile Payload Center Temperature

Time (h)

Tem

pera

ture

(C)



TimeSaver-96 Small PUR



Model Details

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• PCMs are Phase-5 bottles and gel bottles.

• Again, effective conductive heat transfer coefficient used to model imperfect conduction between surfaces



Simulation Results

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Convection Heat Transfer Multiplier : 1/8 (sol’n 1) & 1/16 (sol’n 3)

0 12 24 36 48 60 72 84 96

-15

-10

-5

0

5

10

15

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TimeSaver-96 Small PUR - Winter

Qualification Test #1 Qualification Test #2 Qualification Test #3Payload (Sol'n 1) Payload (Sol'n 3) ISTA Winter 96H

Time (h)

Tem

pera

ture

(C)



Simulation as Part of the Development Process: Case Studies



Modifications to Existing Pallet Shipper Design



Model Details• In order make the REPAK 120

design more robust, the performance of new bottle configurations was examined.

• We wanted to examine the effect of adding an extra bottle to each sleeve.

• By simulating this new configuration, significant prototyping labour and chamber time were avoided.

• Other options may be further explored by modifying the model.



New Panels3-Bottle Panel 4-Bottle Panel



Simulation Results - Summer

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• Simulation results from new designs compared with test results from old design

0 24 48 72 96 1200

5

10

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REPAK 12- Bottom Corner REPAK 13-Bottom Center REPAK 14-Top Corner3-Bottle SIM - Payload Center REPAK 15-Top Center 4-Bottle SIM - Payload CenterREPAK Summer 120H

Time (h)

Tem

pera

ture

(°

C)




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• Simulation results from new designs compared with test results from old design.

• Notably, the initial payload temperature in the test run was less than 5°C.

0 24 48 72 96 120

-30

-25

-20

-15

-10

-5

0

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3-Bottle SIM - Payload Center 4-Bottle SIM - Payload Center REPAK 8-Top CornerREPAK 6-Bottom Corner REPAK 7-Bottom Center REPAK 9-Top CenterREPAK Winter 120H

Time (h)

Tem

pera

ture

(°C)



Pallet Shipper Concept



• A large distributor of medical products expressed interest in a custom pallet shipper capable of transporting a wide variety of temperature-sensitive products for at least 48 hours.

• Customer was very concerned with volume optimization and reusability.

• To help the customer make a more informed decision, the effect of varying PIR wall thickness was modelled.

• Results were obtained within 2 weeks with no prototyping cost.

• Prototype construction and testing would be very costly and take long to complete. Simulation allows us to rapidly evaluate the feasibility of various designs. The results can then be used to help us improve the design.

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¼ view used to exploit symmetry and decrease calculation time

Overview of Project



Simulation Parameters• Wall layers:

• 1/4" HDPE • different thicknesses of PIR were tested (40, 60, and 80 mm)• 1/2" Phase-5• 1/4" HDPE

• Simulated payload: idealized non-fluid material with thermal properties of a bulk air/water blend.

• Temperature profile is a constant 20°C (68°F) for 3 days• Worst-case (top corner) and best-case (center of XY face)

points chosen from the payload surface for post-simulation analysis



Simulation Example


80mm PIR walls, Temperature after 72 hours


0.00 8.00 16.00 24.00 32.00 40.00 48.00 56.00 64.00 72.005.00

6.00

7.00

8.00

9.00

10.00

11.00

12.00

Temperature Response of Pay-load in 20°C (68°F) Flat-line Simu-

lation

40mm Top Corner 40mm Middle of XZ Face 60mm Top Corner 60mm Middle of XZ Face

80mm Top Corner 80mm Middle of XZ Face

Time (hour)

Tem

pera

ture

(C)



Effect of PIR Wall Thickness on PerformancePIR

Thickness (mm)

Wall Thickness (inches)

x ID (in)

y ID (in)

z ID (in)

Volume (in3)

Volume (L)

Payload Top Corner Failure

time (h)

Payload Center of Face Failure Time

(h)

40 2.57 35.85 43.85 72.85 114524 1876 30 47

60 3.36 34.28 42.28 71.28 103279 1692 34 55

80 4.15 32.70 40.70 69.70 92768 1520 62 72+

• Increased PIR thickness has the expected effect of prolonging the period that the payload can be transferred at its safe temperature range of 2 – 8°C.

• The trade-off for longer effectiveness is a decreased payload volume.• By shipping products with lower initial temperatures, the period of effectiveness

can be prolonged.• Many factors, especially the dimensions and the composition of the payload, can

affect these times.



Conclusions• The results of finite element analysis have been

demonstrated and verified with existing designs.• The use of finite element thermal analysis in the

design process presents multiple advantages to our customers: – Comparison of multiple design variations– Rapid analysis of changes to designs– Identification of susceptible locations in the pack-out– Robust design and simulation of large or complex pack-

outs that would entail large cost or time to prototype – Graphical output of models and results



Thank-you for your attention!

Any questions?

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Landon Halloran [email protected]


Technology

The Use of Finite Element Modeling in Thermal Packaging Design