1. The analysis of thermal properties of modern facade systems based on metal sheets
Author: Vedishcheva Iuliia
Research advisor: Maltseva I.N., PhD

2. The task of energy saving is the most priority for all industries, which includes a construction engineering sector too.
It is known that a building loss most quantity of heat energy throw windows and a ventilation system, however, the building loss heat energy through a blank wall and a roof more then it is often taken in a thermotechnical calculation.
Generally, the cause of heat loss is heat conducting inclusions that are inevitable in some types of wall envelopes.

3. Sandwich panels are one of a kind of enclosing structures.

4. A sandwich panel is a three-layers system, including a mineral wood core or a polyurethane foam core or a polystyrol core between two metal sheets

5. We researched the thermal field of a sandwich panel taking into account thermally conductive elements.
The goal of research is an estimation of influence of the thermal uniformity by the thermotechnical properties of enclosure structures (sandwich panel).

6. For achieve the purpose, following analyses were made:
Preliminary analysis of the effect of thermal conductive inclusions on the thermotechnical properties of sandwich panels
The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with horizontal sandwich panels
The comparative analysis of the thermotechnical properties of the vertical and horizontal sandwich panels

7. For this analysis we calculated the sandwich panel model by the fine elements method by use of a CAE-software
We carried out the numerical experiments by the complete multivariable analysis method
For analysis the sandwich panel with following geometry was chosen:
the panel width is 1000 mm;
the panel length is 6000 mm;
the thickness of the flat metal sheets with is 0,5 mm;
the core thickness is 150 mm.

8. The analytical model was defined such the section of a blank wall at the joint of four panels.
The section width is 1000 mm, the section length is 6000 mm.

9. For the numerical experiment we took following materials parameters of the thread forming screws and bolts:
the diameter was taken from 5 mm to 8 mm,
the heat conduction coefficient was taken 44,5 W/(m∙K),
the specific heat was 482 J/(kg∙K),
the density was 7871 kg/m3.
For purpose to mesh simplification and computer assembly resource saving the thread forming screws were simulated with the rectangular cross-section and the thread of the thread forming screws was not simulated.

10. The sheets material had the following characteristics:
the heat conduction coefficient was taken 58 W/(m∙K),
the specific heat was taken 482 J/(kg∙K),
the density was taken 7871 kg/m3.
The panels core was considered as the isotropic material with the variable heat conduction coefficient and with the specific heat and the density were taken for a rook wood – 0,84 J/(kg∙K) and 110 kg/m3.

11. The boundary condition was convection on areas.
Following parameters were adopted for external sheet:
the film coefficient was 23 W/(m3∙K);
the bulk temperature was 238 K (-35 °C).
Following parameters were adopted for internal sheet:
the film coefficient was 8,7 W/(m3∙K);
the bulk temperature was 293 K (20 °C).

12. 1. Preliminary analysis of the effect of thermal conductive inclusions on the thermotechnical properties of sandwich panels
The goals:
Mesh verification
The improvement of the analytical model

13. 1. Preliminary analysis of the effect of thermal conductive inclusions on the thermotechnical properties of sandwich panels
The results:
The preliminary regression equation for calculation of the reduced total thermal resistance of an enclosure structure based on metal sheets for a section of a blank wall was obtained in according to the experiment results:
Rrext = – 0, , ·d + 12, ·10-3·B1 + 1, ·10-3·B , ·λc – 0, ·10-3·d·B1 – 97,9823·10-6·d·B2 – 5,49075·d·λc –
– 2,286·10-6·B1·B2 –194,920977·10-3·B1·λc – 24, ·10-3·B2·λc + 320,8·10-9·d·B1·B , ·10-3·d·B1·λc + +1,561422·10-3·d·B2·λc + 35,079·10-6·B1·B2·λc –
– 5,25155·10-6·d·B1·B2·λc

14. 1. Preliminary analysis of the effect of thermal conductive inclusions on the thermotechnical properties of sandwich panels
The results:
The differences between the thermal resistance of the light-weight enclosure structure based on metal sheets for different step of thermal conductive connections is reduced with increasing of the size of thermal conductive connections

15. 1. Preliminary analysis of the effect of thermal conductive inclusions on the thermotechnical properties of sandwich panels

16. 1. Preliminary analysis of the effect of thermal conductive inclusions on the thermotechnical properties of sandwich panels

17. Size and type of the mesh Δ1= (Rrext- Rrint) Rrext
1. Preliminary analysis of the effect of thermal conductive inclusions on the thermotechnical properties of sandwich panels
The results:
The dependence between the mesh size and the thermal resistance of an enclosure structure based on metal sheets was obtained:
The influence of the meshes size by results accuracy
Size and type of the mesh
Rrext, (m2·К)/W
Rrint, (m2·К)/W
Δ1= (Rrext- Rrint) Rrext
0,008 м Hex+Sweep
2,494981
2,477032
0,7%
0,01 м Hex+Sweep
3,344606
2,29727
2,1%

18. 1. Preliminary analysis of the effect of thermal conductive inclusions on the thermotechnical properties of sandwich panels
The results:
The values of the heat transfer performance uniformity factor with a consideration of influence of thread forming screws are varied into the diapason from to that it is an important factor and it requests corresponding consideration.

19. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The goals:
the solution of the regression equation for the reduced total thermal resistance of an enclosure structure;
the check of sweating possibility at the internal surface of an enclosure structure;
the check of correspondence of the temperature gradient between the internal surfaces of an enclosure structures and the indoor temperature to the government standards.

20. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
According to the results of importance estimation of the influence factors like variation parameters of multivariable analysis planning following factors were accepted:
the diameter of thread forming screws (d);
the transverse spacing between screws (B1);
the longitudinal spacing between screws (B2);
the heat transfer coefficient of core (λc).

21. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The experiment planning matrix у = 24 -1 +1 λ
X1 = d
5,0
6,5
8,0
1,5
X2 = B1
300
400
500
100
X3 = B2
1500
3750
6000
2250
X4 = λc
0,03
0,04
0,05
0,01

22. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The results:
Based on the numerical analyses results, the regression equation for calculation of the reduced total thermal resistance of an enclosure structure based on metal sheets for a section of a blank wall was obtained.
According to the obtained data the diagrams of the dependence Rr = f (d), Rr = f (B1), Rr = f (B2), Rr = f (λc) were formed

23. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The results:
The diagram of dependence of the reduced total thermal resistance of an enclosure structure based on metal sheets for a section of a blank wall to the diameter of thermally conductive elements (Rr = f (d))

24. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The results:
The diagram of dependence of the reduced total thermal resistance of an enclosure structure based on metal sheets for a section of a blank wall on the heat transfer coefficient of a sandwich panel core (Rr = f (λc))

25. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The results:
The diagram of dependence of the reduced total thermal resistance of an enclosure structure based on metal sheets for a section of a blank wall on the longitudinal spacing between screws (Rr = f (B2))

26. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The results:
The diagrams show that dependences between the reduced total thermal resistances of an enclosure structure based on metal sheets for a section of a blank wall and the varied parameters are near liner or liner.
So, the reduced total thermal resistance for a section of a blank wall for vertical sandwich panels:
Rr = 5,9 – 32·10-3d B1 + 0,07·10-3B2 – 72,563·λc

27. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The results:
Based on the research finding the diagrams of dependence of the temperature of internal surfaces of an enclosure structure on the longitudinally and transversely coordinate of the sandwich panel were drawn

28. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The results:
The results are presented for the sandwich panel with following parameters:
λc = 0,05 W/(m·К),
d = 8,0 mm,
B1 = 300 mm,
B2 = 1500 mm

29. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The results:
The results are presented for the sandwich panel with following parameters:
λc = 0,05 W/(m·К), d = 5,0 mm,
B1 = 300 mm,
B2 = 1500 mm

30. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The results:
The standard temperature gradient of the Russian Government Standard between an internal surface of an enclosure structure and indoor temperature are exceeded on an internal surface of an enclosure structure.

31. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The results:
If the indoor temperature is tint = +20°С and the relative room humidity is φ=50%, φ=55% or φ=60% than the temperature on in internal surface of an enclosure structure on fitting locations of sandwich panels to a frame is less than the dewpoint temperature.

32. 2. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with vertical sandwich panels
The results:
So, sweating is possible on fitting elements and it can be the cause of corrosion formation at fitting elements, at a surface of an internal sheet and a panel core in a fixing location of a sandwich panel to a frame and a frame itself.

33. 3. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with horizontal sandwich panels
The goals:
the solution of the regression equation for the reduced total thermal resistance of an enclosure structure;
the check of sweating possibility at the internal surface of an enclosure structure;
the check of correspondence of the temperature gradient between the internal surfaces of an enclosure structures and the indoor temperature to the government standards.

34. 3. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with horizontal sandwich panels
According to the results of importance estimation of the influence factors like variation parameters of multivariable analysis planning following factors were accepted:
the diameter of thread forming screws (d);
the transverse spacing between screws (B1);
the heat transfer coefficient of core (λc).

35. 3. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with horizontal sandwich panels
The experiment planning matrix у = 23 -1 +1 λ
X1 = d
5,0
6,5
8,0
1,5
X2 = B1
300
375
450 75
X3 = λc
0,03
0,04
0,05
0,01

36. 3. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with horizontal sandwich panels
The results:
According the numerical experiment results the regression equation for calculation of the reduced total thermal resistance for horizontal sandwich panels was obtained:
Rr = 6,6 – 10-3d B1 – 80,7·λc

37. 3. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with horizontal sandwich panels
The results:
The standard temperature gradient of the Russian Government Standard between an internal surface of an enclosure structure and indoor temperature are exceeded on an internal surface of an enclosure structure for horizontal sandwich panels.

38. 3. The estimate of influence of the thermal uniformity by the thermotechnical properties of the enclosure structures with horizontal sandwich panels
The results:
The temperature on the internal surface of an enclosure structure is less than the dewpoint temperature for a building if we use fastening elements (bolts) with the diameter 8 mm.

39. 4. The comparative analysis of the thermotechnical properties of the vertical and horizontal sandwich panels
The results:
Following equation can be employed for calculation of the reduced total thermal resistance of an enclosure structures for a blank wall consisted both of vertical sandwich panels and horizontal sandwich panels:
Rr = 5,9 – 32·10-3d B1 + 0,07·10-3B2 – 72,563·λc

40. 4. The comparative analysis of the thermotechnical properties of the vertical and horizontal sandwich panels
The results:
The diagrams of dependence of the reduced total thermal resistance on the heat transfer coefficient of the core and quantity of heat conductivity elements (n).

41. 4. The comparative analysis of the thermotechnical properties of the vertical and horizontal sandwich panels
The results:
The diagram of dependence of the reduced total thermal resistance on the transverse and longitudinal spacing between forming elements and the heat transfer coefficient (Rr=f(В1, В2, λc)) for mounting of sandwich panels to a frame of the tread forming screws with the diameter 6.3 mm

42. 4. The comparative analysis of the thermotechnical properties of the vertical and horizontal sandwich panels
The results:
The diagram of dependence of the reduced total thermal resistance on the transverse and longitudinal spacing between forming elements and the heat transfer coefficient (Rr=f(В1, В2, λc)) for mounting of sandwich panels to frame of the bolts with the diameter 8,0 mm (n is quantity of bolts on one panel).

43. 4. The comparative analysis of the thermotechnical properties of the vertical and horizontal sandwich panels
The results:
For convenience of practice application according to the regression equation calculated based on the results of the numerical researches the equation for calculation of minimal values of temperature on an internal surface of a sandwich panel was obtained:

44. 4. The comparative analysis of the thermotechnical properties of the vertical and horizontal sandwich panels
The results:
The analysis of the thermal field on the internal surface of sandwich panels shown that the thermal gradient between an internal surface of an enclosure structure made of both horizontal and vertical sandwich panels and the indoor temperatures are exceed on fitting locations of panels to frame for public buildings and for industrial buildings with dry and normal humidity conditionals.
This fact results in reduction of human comfort being in a building.

45. 4. The comparative analysis of the thermotechnical properties of the vertical and horizontal sandwich panels
The results:
We recommend following accompanying measures for improvement of the energy efficiency of this types of enclosure structures:
use additional thermal insulation for fitting locations of sandwich panels to a frame by mounting of panel strips with an additional thermal insulation layer (an additional control on building areas during sandwich panels mounting)
use for mounting of sandwich panels to a frame pop rivets that connect to a bottom sheet of a sandwich panel and don’t cut through a sandwich panel like a bolt.
use a thermal insulation tube when we screw in a thread forming screw into sandwich panel

46. 4. The comparative analysis of the thermotechnical properties of the vertical and horizontal sandwich panels
The results:
We recommend following accompanying measures for improvement of the energy efficiency of this types of enclosure structures:
use additional thermal insulation for fitting locations of sandwich panels to a frame by mounting of panel strips with an additional thermal insulation layer (an additional control on building areas during sandwich panels mounting)
use for mounting of sandwich panels to a frame pop rivets that connect to a bottom sheet of a sandwich panel and don’t cut through a sandwich panel like a bolt.
use a thermal insulation tube when we screw in a thread forming screw into sandwich panel

47. 4. The comparative analysis of the thermotechnical properties of the vertical and horizontal sandwich panels
The results:
The alternative of thermal insulation of the fitting location of a sandwich panel to a frame

48. The conclusions
1. For existing types of fixing sandwich panels to a frame, the hygiene requirements are not complied, that is:
1.1. The temperature gradient between an internal surface of an enclosure structure on fitting locations of a sandwich panel to a frame and the indoor temperature are exceeded for public buildings and for industrial buildings with dry and normal humidity conditions.
1.2. The temperature on internal surfaces of an enclosure structure is less than the dewpoint temperature only for using bolts for fixing a sandwich panel to a frame.

49. The conclusions
2. Consideration of the heat transfer performance uniformity factor is necessary for thermotechnical calculation of a sandwich panel wall. Its value is from 0,77 to 0,93 for both horizontal and vertical sandwich panels.
3. Horizontal sandwich panels are more preferable than vertical sandwich panels in the context of energy efficiency.

50. The conclusions
4. The methods of energy efficient improvement of buildings with sandwich panels using like wall enclosure structures are suggested.
5. Recommended guideline abidance for designing and construction in climatological conditions of Sverdlovsk region will help to energy and resource efficiency improvement.

51. Master Degree in Innovative Technologies in Energy Efficient Buildings for Russian & Armenian Universities and Stakeholders – «MARUEEB»
Federal State Autonomous Educational Institution of Higher Education «Ural Federal University named after the first President of Russia B.N.Yeltsin»
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