Aging Characteristics of Polyurethane Foam Insulation

  • J. Navickas
  • R. A. Madsen
Part of the Advances in Cryogenic Engineering book series (ACRE, volume 22)

Abstract

Closed-cell polyurethane foam insulation displays a time-dependent thermal conductivity characteristic commonly known as aging. Freshly made foam has a relatively low thermal conductivity, which increases with time and approaches a significantly larger value. Understanding and predicting this aging process are important in order to establish uniform conditions for comparing foam-measured thermal performance, extrapolation of data for long-term applications, and prediction of performance for service with different gases. Understanding of this foam characteristic is particularly important for cryogenic applications because the aging effects become manifested quicker at low temperatures, before they are apparent in ambient temperature data.

Keywords

Methane Convection Foam Beach Polyurethane 

Notation

C

air concentration

C0

initial air concentration

C1

external air concentration

d

molecular diameter

D

diffusion coefficient

Dfilm

solid Polyurethane film diffusion coefficient

Dfoam

foam diffusion coefficient

h

molecules/volume

k

insulation thermal conductivity

k′

monatomic thermal conductivity of mixture

k″

internal thermal conductivity of mixture

kair-Freon 11

thermal conductivity of air-Freon 11 mixture

kair

air thermal conductivity

kcontinuum

continuum thermal conductivity

kF11

Freon 11 thermal conductivity

ki, kj

monatomic thermal conductivity of i and j species

ki, kj

internal thermal conductivity of i and j species

k0

initial foam thermal conductivity

k(p)

thermal conductivity at low pressure

ksolid

solid Polyurethane film thermal conductivity

L

mean free path

l

typical dimension

Mi, Mj

molecular weight of i and j species

Na

air mole fraction

NF11

Freon 11 mole fraction

Pr

Prandtl number

t

time

Vclosed cells

insulation volume fraction occupied by closed cells

Vopen cells

insulation volume fraction occupied by open cells

Vsolid

insulation volume fraction occupied by solid material

Vtotal

total insulation volume

xi, xj

mole fraction ofi andj species

x

distance from centerline

Greek Symbols

α

thermal accommodation coefficient (considered unity)

γ

specific heat ratio

δ

foam cell diameter

ρfilm

solid Polyurethane film density

ρfoam

foam density

ϕij

coefficient for calculating internal thermal conductivity of gas mixtures

ψij

coefficient for calculating monatomic thermal conductivity of gas mixtures

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References

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Copyright information

© Springer Science+Business Media New York 1977

Authors and Affiliations

  • J. Navickas
    • 1
  • R. A. Madsen
    • 1
  1. 1.McDonnell Douglas Astronautics CompanyHuntington BeachUSA

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