www.cryopak.com

Use of Engineered Phase Change Materials in Cold Chain Packaging Design

Presented By:Anthony Alleva

Technical Services Manager, TCP Reliable, Inc.Healthcare Packaging Conference & Workshops

May 27, 2010

Leveraging New Refrigerant Technologies

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Table of Contents

PCM Science

PCM Selection and Design

Other Considerations

Package Design Case Studies

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Temperature Controlled Packaging 101

The purpose of a temperature controlled package is to maintain an interior thermal environment sufficient to meet the product’s temperature requirements.

Refrigerant packs in combination with insulated containers make up the bulk of temperature controlled packages.

The most commonly employed refrigerant material is water often with some additives to alter its properties.

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Solid – Liquid - Gas

Phase change is when a material changes between the states of matter.

Phase changes can require large amounts of energy to occur.

Common terms:• Melting and Freezing• Evaporation• Condensation

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“Frozen” means “Solid” not “Cold”!

Anything that is in its “solid state” of matter is correctly referred to as “frozen”.

Materials generally have temperatures at which they transition from solid to liquid and liquid to gas but a small percentage of them are at temperatures that humans normally experience.

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Enthalpy of Fusion

The Enthalpy of Fusion is the amount of thermal energy which must be absorbed or released for a substance to change state from solid to liquid or liquid to solid.• Often also referred to as the

Latent Heat of Fusion

While a material is melting or freezing it stays constant at its phase change temperature.

This property is used to control the temperature inside of the package.

MaterialMelting Point

(°C)

Enthalpy of

Fusion

(kJ/kg)

Helium -269.65 5.23

Hydrogen -259.31 58.6

Nitrogen -209.97 25.5

Oxygen -218.79 13.8

Ethyl Alcohol -114 104.2

Mercury -39 11.8

Water 0 334

Sulfur 119 38.1

Lead 327.3 24.5

Antimony 630.5 165

Silver 960.8 88.3

Gold 1063 64.5

Copper 1083 134

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Why Water?

Water is a common material used in refrigerant packs as it is relatively cheap and ubiquitous.

Water undergoes its solid to liquid phase change at 0 °C / 32 °F which is useful for keeping items “cold”.

Water has a relatively high level of heat capacity as it goes through its freezing and thawing process and can be relied upon to maintain that 0 °C temperature for long periods of time.

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Phase Change Materials (PCM’s)

A PCM is a material chosen for use in an application due to its phase change properties. Normally it is the solid-liquid phase change that is utilized.

While water is correctly referred to as a Phase Change Material, the packaging industry usually excludes water from the category when discussing PCM’s.

The goal is to match the phase change temperature with the product temperature requirements as the PCM will naturally maintain that temperature while melting or freezing.

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PCM Selection

First and foremost a PCM must have a phase change temperature within the desired range and ideally centered within the range.

If the temperature range has only one limit the PCM temperature should be near the limit but still within the range.

Should have performance characteristics that allow it to be a reasonable replacement for water.

Product

Temperature

Range

PCM Temperature

2°C to 8°C 5°C

15°C to 30°C 22°C

-10°C to 10°C 0°C

Below 30°C 25°C to 28°C

Below -10°C -25°C to -15°C

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Water is the Standard of Comparison

Most current temperature control packaging applications are using water as the PCM and as a results, the industry has become used to those systems.• Water has:

• Consistent, repeatable, reliable phase change temperature. • High Enthalpy of Fusion, long time to melt.• Safe, Non-Toxic (Inhalation of large amounts is fatal though)• Easily packaged into “gel packs” or “cold pack bottles”.• Very inexpensive and easy to obtain.

• A “good” PCM will mimic these properties but change phase at a desired temperature.

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When Designing a PCM

Use a Pure Chemical• Search published tables of Phase Change

temperatures for chemicals that have natural Phase Change temperatures within the desired range.

• Cull out materials that have undesirable qualities:• Have low Enthalpies of Fusion or Human Toxicity.• Cannot be easily purchased or manufactured into a

refrigerant.• Are too expensive to be feasible in a packaging application.

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Case Study:Deuterium Oxide

D20 (Also known as Heavy Water) is water that contains a very high (99%+) concentration of the deuterium isotope. Best known for its use in nuclear fusion reactors.

Phase Change Temperature: Approximately 4°C, Repeatability expected to be high.

Enthalpy of Fusion: A small amount greater than regular water.

Toxicity: Low (drinking very large quantities results in death).

Packaging: Can be contained in any material that can contain water.

Ease of Manufacture: Exists in all water at approximately 0.03% by weight. Just needs to be distilled through electrolysis. 400 gallons of water yields 1lb of D20.

Cost: Approximately $100 per 0.25 lbs.

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Designing a PCM

Use a Mixture of Two (or more) Chemicals

Binary Phase Diagram is a graph of the phase change temperature of a mixture of two chemicals showing the relationship between the relative concentrations and the phase states.

The Eutectic Point is the temperature and concentration that the mixture crystallizes simultaneously.

(Diagram from http://www.uwgb.edu/dutchs/petrolgy/BEUTECT.HTM)

Eutectic Point

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Case Study:Water / Ethylene Glycol Mixture

Water mixed with Ethylene Glycol is commonly referred to as “antifreeze” and is used in cars as the engine coolant.

Phase Change Temperature: Eutectic Point is approximately -50°C at just under 60% Ethylene Glycol concentration.

Enthalpy of Fusion: Ethylene Glycol is 160 kJ/kg and water is 334 kJ/Kg (mixture will be between those values).

Toxicity: Moderate to Low (drinking Ethylene Glycol can in death but is mitigated by water). (Diagram from

http://www.uwgb.edu/dutchs/petrolgy/BEUTECT.HTM)

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Case Study:Water / Ethylene Glycol Mixture

Packaging: Can be contained in any material that can contain water.

Ease of Manufacture: Antifreeze is very commonly available.

Cost: Approximately $0.50 per pound. (Diagram from

http://www.uwgb.edu/dutchs/petrolgy/BEUTECT.HTM)

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The T Problem: Time to Freeze/Melt

This equation can be used to calculate heat absorption:

The amount of heat absorbed is proportional to the difference (delta) in temperature between the phase change and the environment.

Higher offsets in temperature will result in faster energy flow resulting in faster phase changes.

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Experimental Example: The T Problem

Compare the Phase Change of Three PCM’s Materials chosen:

• Water Gel: Phase Change at 0°C• Phase 5: Phase Change at 5°C• Phase 22: Phase Change at 22°C

Test Set-Up• Cube of PCM encased in Cube of Polystyrene• Freeze/Thaw all three samples and monitor the

temperatures of each

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Photo of Cube Test Set-Up

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Result for Freezing

Comparison of Freezing of Three PCM's

-40

-30

-20

-10

0

10

20

30

40

0 6 12 18 24 30 36 42 48

Time(h)

Te

mp

era

ture

(°C

)

Ambient Phase 5 Water Gel Phase 22

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Result for Melting

Comparison of Melting of Three PCM's

-40

-30

-20

-10

0

10

20

30

40

48 54 60 66 72 78 84 90 96

Time(h)

Te

mp

era

ture

(°C

)

Ambient Phase 5 Water Gel Phase 22

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Conclusions from Experiment : The T Problem

The ambient temperature is a large factor in time to freeze or melt of a PCM.

The closer the ambient temperature is to the PCM’s melting point the longer it will last.

Once a PCM completes its phase change it has little ability to absorb energy.

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Dry Ice: A Special Case

Dry Ice is Carbon Dioxide in its Frozen State

The phase change it undergoes is called “Sublimation” which means it changes phase directly from solid to gas, skipping the liquid phase.

Dry Ice is made by cooling and pressurizing CO2

Phase Change Temperature is -78.5°C

Cost is around $1 to $2 a pound.

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Dry Ice: Breaking the Law

Very difficult to store• To prevent it from sublimating it would need to be kept in a freezer

maintaining below -78.5°C or kept under pressure.• As it sublimates it turns into gas which is difficult to capture and reuse.

Dry Ice is considered a shipping hazard• CO2 replaces oxygen in the human body as it is inhaled causing

unconsciousness.• There are regulations on how much can be shipped on an airplane.

Sublimation of the Dry Ice inside of a package cause empty space.• The package must be designed to survive the loss of its contents from a

shock and vibration perspective.

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Dry Ice: Mitigating Factors

Dry Ice has a very high Enthalpy of Sublimation at 571 kJ/kg. (Water’s Enthalpy of Fusion is 334 kJ/kg)

The high heat capacity makes up somewhat for the high T of the -78.5°C phase change temperature.• Compare to water:

• 517/334 = 1.7x• (20- - 78.5)/(20-0) = 4.9

• Ratio of weights = 2.9 lbs of Dry Ice vs. 1 lb of water.

Dry Ice is inexpensive and common ($1-$2 per lb).

From an environmental waste perspective, Dry Ice is a wonderful material as it naturally turns into “air” as opposed to “garbage”.

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Dry Ice Performance Example

Example Dry Ice Temperature Profile

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

0 6 12 18 24 30 36 42 48 54 60

Time(h)

Te

mp

era

ture

(°C

)

18 lbs of Dry Ice Ambient

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Other Considerations: Insulation

Passive temperature control can only be achieved if something in the packaging system naturally controls its temperature.

The PCM’s role in the temperature controlled package is to provide the energy for the system and act as the temperature regulator.

The performance of the PCM cannot be uncoupled from the packaging system.

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Experiment: Insulation Quality and Freeze Time

Test Set-Up• All Containers included one (1) 8” x 8” Bag, 2 lb Gel

Pack with the Thermocouple placed inside the bag at the center of the gel.

• All containers had an outer dimension of 12”x12”x12”• Empty Corrugated RSC Box• Expanded Polystyrene Lined RSC • Vacuum Insulated Panel Lined RSC

Question• What relationship does package insulation have to the

time it takes a gel pack to freeze?

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Insulation Quality vs. Time

Comparison of Freezing within 3 Insulations

-30

-20

-10

0

10

20

30

0 12 24 36 48 60 72 84 96

Time(h)

Te

mp

era

ture

(°C

)

Empty Box EPS Box VIP Box Ambient

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Other Considerations: Combining PCM’s

PCM’s with different phase change temperatures can be used together to result in performance that neither would have alone.

Example: Temperature Range of 0°C to 30°C• Use a liquid state 5°C PCM in combination with a solid state 25°C PCM.• One PCM protects from “cold”, the other from “heat”.

Example: Temperature Range of 2°C to 8°C• Use a liquid state 5°C PCM in combination with a solid state 0°C PCM.• The solid PCM melts transferring its energy to the liquid PCM which

freezes and transfers the 5°C temperatures to the payload.

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Experiment: Combination of 5°C PCM and 0°C PCM

Test Set-Up• EPS Insulated package with a water bottle as the payload.

• Payload surrounded with liquid state 5°C PCM (Phase 5) conditioned to 7°C.

• 5°C PCM surrounded by solid state 0°C PCM (Water Gel) conditioned to -20°C.

• Thermocouple recorded payload temperature.

Questions• Is the payload maintained between 2°C and 8°C?

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Results for Combination Experiment

Combination of 5°C PCM and 0°C PCM

0

5

10

15

20

25

30

35

40

0 6 12 18 24 30 36 42 48

Time(h)

Tem

per

atu

re(°

C)

Ambient Payload

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Package Design Case Studies

The examples that follow showcase the various uses of PCM’s discussed in the previous slides.• Dry Ice packages• Combination PCM packages• Packages designed for various temperature control

ranges and products.

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Temperature Range: Below –20°C (Dry Ice)

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

0 5 10 15 20 25 30 35 40 45 50

Time (h)

Tem

per

atu

re (

°C)

T/C 101 T/C 102 T/C 103 T/C 104 T/C 105 Ambient1 Ambient2

EPS Lid

EPS Collar with cut out for monitor

EPS Product Housing

Outer EPS Trough Housing

Lower EPS Collar

EPS Bottom

Outer shipper with EPS

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Temperature Range: –40°C to –20°CEPS Lid

Corrugate Divider

-20°C PCM

Dry Ice

-20°C PCM

Outer shipper with EPS

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Temperature Range: 2°C to 8°CEPS Lid

Refrigerated Water Gels

Frozen Water Gels

Payload Carton

Outer shipper with EPS

Frozen Water Gels

0

5

10

15

20

25

30

35

40

45

0 8 16 24 32 40 48

Time(h)

Tem

pera

ture

(°C

)

Dtmp-1-Ambient Dtmp-4-Product Dtmp-8-Product

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Temperature Range: 2°C to 8°C

EPS Lid

Water Gels

5°C PCM

Outer shipper with dual chamber EPS walls

0

5

10

15

20

25

30

35

40

0 6 12 18 24 30 36 42 48

Time (h)

Tem

per

atu

re (

°C)

T/C 6 10 T/C 6 11 T/C 6 12 T/C 6 18 Ambient T/C 6 19 Ambient High Low

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Temperature Range: 15°C to 30°C

EPS Lid

22°C PCM

Outer shipper with EPS

22°C PCM

Payload

-15

-10

-5

0

5

10

15

20

25

30

0 6 12 18 24 30 36 42 48

TIME(H)

TE

MP

ER

AT

UR

E(C

)

Dtmp-1-Ambient Dtmp-2-BOX 1 Dtmp-4-BOX 2 Dtmp-5-BOX 3

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Temperature Range: Below 37°C

EPS Lid

Thermos Lid

27°C PCM Vial Holder

Thermos

Outer shipper with EPS

0

5

10

15

20

25

30

35

40

45

50

0 4 8 12 16 20 24 28 32 36 40 44 48

Time(H)

Te

mp

era

ture

(C)

Chamber Ambient Data Logger High Limit

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Questions?

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Thank you!Anthony Alleva

Technical Services Manager

TCP Reliable, Inc.551 Raritan Center Parkway

Edison, NJ 08837

Tel: 732-346-9200 x 107

Email: aalleva@tcpreliable.com

Credit to: Jason HeberleProject Manager

DDL, West

www.cryopak.com

Use of Engineered Phase Change Materials in Cold Chain Packaging Design

Presented By:Anthony Alleva

Technical Services Manager, TCP Reliable, Inc.

Leveraging New Refrigerant Technologies