Thermal Performance Analysis of PCM Enhanced Insulations · modeling of the PCM-enhanced building...

© Fraunhofer USA 2009

Fraunhofer Center for Sustainable Energy Systems

Thermal Performance Analysis of PCM-Enhanced Insulations

Jan Kosny Ph.D.

August 10, 2011 Denver ,CO

Building America Meeting Aug. 08 - 11, 2011


Agenda

Introduction – A need for new thermal-design principles for modern buildings Motivation – A need for detailed thermal characteristics of new dynamic

materials to be used in Building America projects Dynamic testing with use of Heat Flow Meter Apparatus New Performance Label for PCMs Potential for development of the material database for PCM products

used in Northern America

Building America Meeting Aug. 08 - 11, 2011 2


Need for a New Thermal Design Principles for Modern Low-Energy Buildings



Today, Building Enclosures Work More as Thermal Shields

4

Interior Environment

Exterior Environment


North American Houses are Currently Built Using Igloo Principles - Developed for Large and Static Temperature Differences

Steady-state code requirements Steady-state design principles

Steady-state testing


Energy Design Paradigm Proposed for Building America

Projects


MOTIVATION (I): Conventional Insulations are not Always Efficient in High-R-value Assemblies



Energy consumption change GJ/year

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

6 to 10

10 to

14

14 to18

18 to

22

22 to26

26 to

30

30to

34

34to

38

38 to42

42

to 46

46

to 50

50 to

54

54to

58

Atlanta Bakersfield Chicago Denver Houston Knoxville Miami Minneapolis Phoenix Seattle Washington DC

X starting attic R-value

X

R-4

GJ/

year

Example #1: Conventional insulation works only effectively for low R-value assemblies



Example #2: Performance of Conventional Insulations can be Easily Improved by Usage of Modern Insulation Configurations

0.20

0.10

0.00

-0.10

6

R-100

12 18 24 30

Two summer days

36 42

R-5

R-50 -0.20

-0.30

-0.40

R-50 -0.50

time [h]

R-50 roof shingle R-100 roof shingle

R-5deck R-50 PCM R-5deck R-50

R-50

R-5 PCM 18.5 BTU per ft2

Btu

/ft2-

h


MOTIVATION (II):Several PCM-Enhanced Systems Successfully Used in Europe are Ineffective While Used in Northern America – Why?



Old Approach – PCM-Impregnated Gypsum Board

PCM charged by interior temperature swings and solar gains through glazing

Building HVAC system used to discharge PCM

Schematic of Distribution of Heating and Cooling Loads in Old PCM Applications

Energy Discharged Later

Cavity Insulation

PCM-Gypsum Board

Exterior Finish

Exterior

Interior

Peak Loads Energy Transferred Back to the Environment

by HVAC System Solar Gains Energy Transferred INTO the Building


Main Problem with Application of PCM Gypsum Boards in the U.S. Air-Conditioned Buildings

Enthalpy for commonly-used paraffinic PCM Thermostat temperature control +/-2degF

30

15

0

-15

-30

-45

16 17 18 19 20 21 22 23 24 25 26

TEMPERATURE [C]

45

[J/g

]

melting freezing


MOTIVATION (III): Traditional DSC Testing is NOT USEFUL for Many Non-Uniform and Complex PCM Products



Large Selection of Non-Uniform PCMs is in common use today which cannot be tested in DSC

PCM blend


Complex arrays of PCM containers are extremely difficult to test in conventional equipment Example of estimation of the measure area for the arrays of PCM pouches or PCM containers.

Measure area needs to contain representative geometry of the measured array of PCM containers



Complexity of H Enthalpy Data for PCM-Enhanced Insulations and blends

Initial Differential Scanning Calorimeter (DSC) tests for pure PCMs or PCM microcapsules, only

Additions to PCM-based blends make a difference; Dynamic Heat Flow MeterApparatus tests were introduced in 2006 for PCM-enhanced insulations - fire retardant effect, adhesives, not-working PCM pellets, etc….

0.00

2.00

4.00

6.00

8.00

10.00

12.00

16.00 18.00 20.00 22.00 24.00 26.00 28.00

Temp [deg C]

J/g

DSC 80% 67%


New Dynamic Test Method for PCM-Enhanced Products Developed by Fraunhofer CSE



Dynamic Test Methods Considered Currently for Analysis of PCM-Enhanced Products

DSC – only for uniform PCMs T-history method Dynamic Heat Flow Apparatus Method

• Symmetrical process • Non-symmetrical process

Dynamic Guarded Hot-Plate Method – only speculations so far Dynamic Hot-Box Method



Testing Temperature Profile Used by Fraunhofer CSE -Symmetrical Testing on Both Plates of the HFMA

Temp.

Time

Melting Temp.

Initial Temp.



Limit Limit

16 17 18 19 20 21 22 23 24 25 26

Temperature Range of Phase Change Process

Key Temperatures of the PCM Transition Process

Temperature 45

30

15

0

-15

-30

-45

TEMPERATURE [C]

Enthalpy for commonly-used paraffinic PCM Lower Upper

Temperature

[J/g

]

melting freezing


Enthalpy change profile developed during Dynamic Heat Flow Meter Apparatus Testing

7.0E+06

6.0E+06

5.0E+06

4.0E+06

3.0E+06

2.0E+06

1.0E+06

0.0E+00 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40

Volu

met

ric H

Pro

file,

J/(m

3 )

Volumetric H (A) Volumetric H (B) Volumetric H (C)

Temperature, C



MOTIVATION (IV): Results from Traditional DSC Testing Can be Misused



Rate of Temperature Change Effects Enthalpy Profiles

Estimation of upper and lower temperature limits for sample of the PCM-enhanced material or composites using original DSC test data for PCM (paraffinic PCM data shown).


© Fraunhofer USA 2009 24ITCC - June 26 - 30, 2011

Enthalpy for commonly-used paraffinic PCM

Potential area for misuse of the experimental data on PCM-enhanced products for most-likely marketing purposes

For what temperature range PCM enthalpy should be calculated if cp-related effects are included together with phase transition–related effects?

45

30

15

0

-15

-30

-45

TEMPERATURE [C]

This one?

16 17 18 19 20 21 22 23 Or, this one ???

24 25 26[J/g

]

melting freezing


M-value – New Energy Performance Label for PCM-Enhanced Products Expressing only phase transition-related enthalpy change



Understanding of Enthalpy Profile in estimation of M-value

H

Temp.

It is possible to analytically estimate and later subtract cp-related enthalpy changes for both frozen and melted stages of the testing.



Basic Heat Transport Equations: The one-dimensional heat transport equation for such a case is as follows:

where; ρ and λ are the material density and thermal conductivity, T and h are temperature and enthalpy per unit mass. Heat flux q is given by:

The enthalpy derivative over the temperature (with consideration of constant pressure) represents the effective heat capacity, with phase change energy being one of the components:

Effective heat capacity, ceff, for a material which is a blend of insulation and PCM may be expressed as

where α denotes the percentage of PCM, cins the specific heat of insulationwithout PCM and ceffPCM is effective heat capacity of PCM.

Th t x x

, ,

T x t q x t

x

eff h c T T

1eff ins effPCM c c c



Practical determination of M-value based on the DHFMA data


0.0E+00

2.0E+05

4.0E+05

6.0E+05

8.0E+05

1.0E+06

1.2E+06

1.4E+06

1.6E+06

1.8E+06

2.0E+06

2.2E+06

2.4E+06

2.6E+06

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40

Volu

met

ric s

peci

fic h

eat,

J/(m

^3 K

)

Temperature, C

Volumetric Heat Capacity A

Volumetric Heat Capacity B

Volumetric Heat Capacity C

cp related change for cp related change frozen PCM for melted PCM

Phase transition

range

Subtract cprelated

change for melted PCM

Subtract cprelated

change for frozen PCM

>5% enthalpy

change per temperature

step

28


New energy performance label for PCM-enhanced products



ITCC - June 26 - 30, 2011

Future Work within Building America Program

Dynamic testing of PCM-enhanced materials used in the U.S. Development of Energy Plus and BEopt modules enabling

modeling of the PCM-enhanced building assemblies Comparisons of DHFMA data against DSC or T-history test data Modeling leading to optimization of the temperature range and

PCM load – as a function of application thermal conductivity, location, and thickness Development of configuration recommendations for PCM

applications in basic U.S. climates


© Fraunhofer USA 2009 Building America Meeting Aug. 08 - 11, 2011

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