Analytical Models for Calculating Thermal Bridge Effects Caused by Thin High Barrier Envelopes around Vacuum Insulation Panels

Abstract

Although vacuum insulation panels (VIPs) are thermal insulators with very low center-of-panel thermal conductivity, their effective thermal conductivity is raised significantly due to large edge heat fluxes caused by a continuously enveloping high barrier laminate, especially if metal based foils are applied. This study therefore presents and validates two analytical approximating models for calculating this thermal edge effect for thin high barrier laminates around VIPs. A comparison of these models with numerical simulations shows that they can be applied with an inaccuracy of <5% for idealized barrier laminates, considering the limitations specified. These models also demonstrate that the linear thermal transmittance, representing this edge effect, amongst others depends on envelope thickness and thermal conductivity, panel thickness, and center-of-panel thermal conductivity. Moreover, this study shows that these models are able to estimate the linear thermal transmittance resulting from more realistic VIPs with seams near their edges, as well. For these realistic panels, deviations between numerical data and prediction model maximally amount to about 9%. Using the presented models then, enables VIP designers, architects, and building engineers to estimate the overall thermal performance of a VIP.

Keywords

vacuum insulation panels heat transfer thermal bridging simulation analytical models linear thermal transmittance

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References

Brodt, K. (1995). Thermal Insulations: Cfc-Alternatives and Vacuum Insulation, PhD Thesis, Department of Applied Sciences, Delft University of Technology, Delft, The Netherlands.

Bundi, R. (2003). Vakuumisolierte Paneele. Forschung und Entwicklung im Fassadenbau, Fassade, 2003(3): 19-22.

Caps, R. , Heinemann, U. , Ehrmanntraut, M. and Fricke, J. (2001). Evacuated Insulation Panels Filled with Pyrogenic Silica Powders: Properties and Applications , High Temperatures-High Pressures, 33(2): 151-156 .

Collins, R. E. and Simko, T. M. (1998). Current Status of the Science and Technology of Vacuum Glazing , Solar Energy, 62(3): 189-213 .

Ghazi, W. K. , Bundi, R. and Binder, B. (2004). Effective Thermal Conductivity of Vacuum Insulation Panels , Building Research and Information, 32 (4): 293-299 .

NEN-EN-ISO 10077-1 (2004). Thermische eigenschappen van ramen, deuren en luiken - Berekening van de warmtedoorgangscoefficient - Deel 1: Algemeen, Nederlands Normalisatie Instituut.

NEN-EN-ISO 10211-1 (1995). Thermal Bridges in Building Construction - Heat Flows and Surface Temperatures - Part 1: General Calculation Methods, Nederlands Normalisatie Instituut .

NEN-EN 13947 (2000). Thermische eigenschappen van vliesgevels - Berekening van de warmtegeleiding - Vereenvoudigde methode, Nederlands Normalisatie Instituut.

Nussbaumer, T. , Bundi, R. , Tanner, Ch. and Muehlebach, H. (2005). Thermal Analysis of a Wooden Door System with Integrated Vacuum Insulation Panels , Energy and Buildings, 37(11): 1107-1113 .

10.

Nussbaumer, T. , Ghazi, W. K. and Tanner, Ch. (2006). Experimental and Numerical Investigation of the Thermal Performance of a Protected Vacuum-Insulation System Applied to a Concrete Wall , Applied Energy, 83(8): 841-855 .

11.

Physibel (2000). TRISCO Manual of Version 10.0 w, Physibel, Maldegem.

12.

Rath, D. (1989). Warmetransport in evakuierten Dammsystemen, PhD Thesis, Universitat Dortmund, Dortmund, Germany.

13.

Schwab, H. , Stark, C. , Wachtel, J. , Ebert, H.-P. and Fricke, J. (2005). Thermal Bridges in Vacuum-insulated Building Facades , J. of Thermal Env. and Bldg. Sci., 28(4): 345-355 .

14.

Simmler, H. and Brunner, S. (2005). Vacuum Insulation Panels for Building Application. Basic Properties, Aging Mechanisms and Service Life , Energy and Buildings, 37(11): 1122-1131 .

15.

Stovall, T. K. and Brzenzinski, A. (2002). Vacuum Insulation Round Robin to Compare Different Methods of Determining Effective Vacuum Insulation Panel Thermal Resistance, In: Desjarlais, A. O. and Zarr, R. R. (eds), Insulation Materials: Testing and Applications, Volume 4, STP 1426, American Society for Testing and Materials (ASTM), West Conshohocken, USA .

16.

Thorsell, Th. I. and Kallebrink, I. (2005). Edge Loss Minimization in Vacuum Insulation Panels , In: Johannesson, G. A. (ed.), In: Proceedings of the 7th Symposium on Building Physics in the Nordic Countries, June 13-15, 2005, Reykjavik, The Icelandic Building Research Institute, pp. 945-952 .

17.

Went, K. van (2002). Vacuum isolatie panelen, MSc Thesis, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, The Netherlands.

18.

Willems, W. M. , Schild, K. and Hellinger, G. (2005). Numerical Investigation on Thermal Bridge Effects in Vacuum Insulating Elements , In: Proceedings of the 7th International Vacuum Insulation Symposium, EMPA, Dubendorf, September 28-29, 2005, pp. 145-152 .