determination method of thermalconductivity of building parts in situthrough ir imaging by...

8/6/2019 DETERMINATION METHOD OF THERMALCONDUCTIVITY OF BUILDING PARTS IN SITUTHROUGH IR IMAGING BY MINIMIZING THEINFLUENCE OF ENVIRONMENTAL PARAMETERS G. FIV

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DETERMINATION METHOD OF THERMAL

CONDUCTIVITY OF BUILDING PARTS IN SITU

THROUGH IR IMAGING BY MINIMIZING THE

INFLUENCE OF ENVIRONMENTAL PARAMETERS

G. FIVOS SARGENTIS, A. CHATZIMPIROS and N. SYMEONIDIS

11th International Conference on Environmental Science and TechnologyChania, Crete, Greece, 3 5 September 2009


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INTRODUCTION


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INTRODUCTION


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INTRODUCTION


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INTRODUCTION


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INTRODUCTION


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INTRODUCTION


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INSIDE

TEMPERATURE

2

Q1

Q

t La

1x

2 3Q

dx

OUTSIDE

2t

Lit

1t

aaC ia

t2

x'1

xd

2

Q

Lat

Q1

Q32

C a a a i

t1

tLi

C

t2

x1

x2

d

Lat

Q1

Q3

Q2

a a a i

t1

tLi

Qs

Qs1

Qs2

Qs3

I N S I D E

TEMPERATURE

OUTSIDE INSIDE

TEMPERATURE

OUTSIDE

The variation of the surface temperatures in three cases: (a) theoretical, (b) in

case of win (blue arrows) and (c) in case of solar radiation (red arrows)

INTRODUCTION


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4.0C

19.0C

5

10

15

13,3C

31,0C

15

20

25

30

AR01

AR02

METHOD DESCRIPTION Test example


10/18

5

0

tL

d

10

152

t

C

20

t1

Lit

0

5

15

10

dd

2t

Lt

1t

tL

0

5

10

15

C

20

Lit

2t

C

20t

1

Lit

+ ~~

Qs

TEMPERATURE

t

5

0

tL

d

10

15

20

tt 1

2

C

Li

TEMPERATURE

TEMPERATURE

TEMPERATURE

Environmental aspects of infrared imaging testing

METHOD DESCRIPTION


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In this method of analysis, the parameters used are:

tLa: outside temperature

tLi: inside temperature

t1 : surface temperature (interior)

t2 : surface temperature (exterior)

ax

: surface conductivity

K: thermal conductivity of part of the buildings envelope

R: thermal resistance of part of the buildings envelope =1/K

: thermal resistance of the material

K

Calculations

L1

METHOD DESCRIPTION

?


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aFAN

CalculationsMETHOD DESCRIPTION


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1/

aFAN

ai

K



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1/

aa

ai

K in situ



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K in situ KAbsence of solar influence

94% 74%

efficiency factor:

1,00

2,00

3,00

4,00

5,00

6,00

7,00

1,00 2,00 3,00 4,00 5,00 6,00 7,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

1,00 2,00 3,00 4,00 5,00 6,00 7,00



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K in situ KPresence of solar influence

70% 67%

efficiency factor:

1,00

2,00

3,00

4,00

5,00

6,00

7,00

1,00 2,00 3,00 4,00 5,00 6,00 7,00

1,00

2,00

3,00

4,00

5,00

6,00

7,00

1,00 2,00 3,00 4,00 5,00 6,00 7,00



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Difficulties in applying the method in specific type of materials with high thermal

storage capacity, such as stone.

Experimental data show that for the application of the method for the calculation of the

thermal conductivity in this type of materials, the following conditions should apply:

Elimination of environmental interruption (solar energy, wind)

Maximization of the temperature difference (indoor outdoor)

Stable thermal flow for more than three hours

Therefore, the optimal measurement is taken during cold winter nights, and at the

same time when inside temperature of the building is the highest possible.

So the method is defined to provide results for the thermal behaviour of different parts

of a building with precision of more than 80% if the following conditions apply:

Stable thermal flow between indoor and outdoor system for more than 1

hour

Minimum variation of the outdoor temperature

Difference between indoor and outdoor temperatures superior to 15C

No measurements are taken while there is solar radiation on the building.

DISCUSSION


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CONCLUSIONS

Through this method, infrared imaging, mostly used as an

approach for qualitative analysis in buildings, becomes aquantitative analysis tool for improving the accuracy of the

in situ determination of the thermal conductivity of

buildings materials.

Based on this method, existing buildings parts can beevaluated quantitatively with regard to their thermal

conductivity, which is related to the buildings energy

requirements. In addition, failures in buildings envelopes,

such as thermal bridges, can be detected and analysed

quantitatively, while also measures for improving theinsulation of buildings can be evaluated through

quantitative and accurate data.

determination method of thermalconductivity of building parts in situthrough ir imaging by...

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