scholarly journals Measurements of thermal Transmittance of an External massive timber wall in-situ and in the Laboratory

2020 ◽  
Vol 172 ◽  
pp. 14009
Author(s):  
Christoph Geyer ◽  
Andreas Müller ◽  
Barbara Wehle
Keyword(s):  
In Situ Measurement ◽  
Test Results ◽  
Mean Values ◽  
Thermal Transmittance ◽  
University Of Applied Sciences ◽  
Measurement Results ◽  
State Boundary ◽  
U Value ◽  
Massive Timber

The thermal transmittance of an exterior massive timber wall was measured in situ in Appenzell, Switzerland according to the standard ISO 9869-1. The measurements were performed with two different measurement sets in parallel. The measurements started in February and stopped at end of April. The measuring data were analyzed using mean values of the thermal transmittance coefficient and of the thermal resistance following the procedure of ISO 9869-1. In order to clarify if the in-situ measurement results show significant deviations from the measurement results of the thermal transmittance obtained in the laboratory, the thermal transmittance of the identical wall construction was measured in the laboratory of Bern University of Applied Sciences in Biel according to the standard EN ISO 8990 for steady state boundary conditions in a guarded and calibrated hot box. The test results will be presented and the measurement setup will be described. The calculation value of the thermal transmittance coefficient of the massive timber wall according to EN ISO 6946 is U = 0.53 W/(m2K). The test results of the thermal transmittance coefficient, U-value of the wall, measured in the hot box, agreed well within a confidence level of 95 % with the calculated value. The in-situ measurement results of the thermal transmittance coefficient of the two measurement sets differ significantly in the order of 8 % referred to the calculated U-value of the wall as the basic amount. Furthermore, both in situ test results of the U-value of the wall show significant deviations from the calculated U-value up to 27 %.

scholarly journals Analysis of Convergence Characteristics of Average Method Regulated by ISO 9869-1 for Evaluating In Situ Thermal Resistance and Thermal Transmittance of Opaque Exterior Walls

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1989 ◽  
Author(s):  
Doo Sung Choi ◽  
Myeong Jin Ko
Keyword(s):  
Thermal Resistance ◽  
Average Method ◽  
Test Duration ◽  
Test Environment ◽  
Building Envelopes ◽  
Thermal Transmittance ◽  
The Third ◽  
U Value ◽  
R Value

In the last few decades, an average method which is regulated by ISO 9869-1 has been used to evaluate the in situ thermal transmittance (U-value) and thermal resistance (R-value) of building envelopes obtained from onsite measurements and to verify the validity of newly proposed methods. Nevertheless, only a few studies have investigated the test duration required to obtain reliable results using this method and the convergence characteristics of the results. This study aims to evaluate the convergence characteristics of the in situ values analyzed using the average method. The criteria for determining convergence (i.e., end of the test) using the average method are very strict, mainly because of the third condition, which compares the deviation of two values derived from the first and last periods of the same duration. To shorten the test duration, environmental variables should be kept constant throughout the test or an appropriate period should be selected. The convergence of the in situ U-value and R-value is affected more by the length of the test duration than by the temperature difference if the test environment meets literature-recommended conditions. Furthermore, there is no difference between the use of the U-value and R-value in determining the end of the test.

scholarly journals Comparison of Infrared Thermography and Heat Flux Method for Dynamic Thermal Transmittance Determination

Buildings ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 132 ◽  
Author(s):  
Mergim Gaši ◽  
Bojan Milovanović ◽  
Sanjin Gumbarević
Keyword(s):  
Heat Flux ◽  
Infrared Thermography ◽  
Dynamic Method ◽  
Flux Method ◽  
Microsoft Excel ◽  
Experimental Procedure ◽  
Thermal Transmittance ◽  
U Value ◽  
Stationary Heat Transfer

This paper proposes an alternative experimental procedure that uses infrared thermography (IRT) for measuring the surface temperature of building elements, through which it is possible to approximate the thermal transmittance or the U-value. The literature review showed that all authors used similar procedures that require semi-stationary heat transfer conditions, which, in most cases, could not be achieved. The dynamic and the average methods that are given in ISO 9869 were also used with the IRT and the heat flux method (HFM). The dynamic method (DYNM) shows a higher level of accuracy compared to the average method (AVGM). Since the algorithm of the DYNM is more complicated than that of the AVGM, Microsoft Excel VBA was used to implement the algorithm of the DYNM. Using the procedure given in this paper, the U-value could be approximated within 0–30% of the design U-value. The use of IRT, in combination with the DYNM, could be used in-situ since the DYNM does not require stable boundary conditions. Furthermore, the procedure given in this paper could be used for relatively fast and inexpensive U-value approximation without the use of expensive equipment (e.g., heat flux sensors).

Two new methods for the in-situ measurement of the overall thermal transmittance of cold frame lightweight steel-framed walls

2018 ◽  
Vol 170 ◽  
pp. 183-194 ◽  
Author(s):  
Ioannis A. Atsonios ◽  
Ioannis D. Mandilaras ◽  
Dimos A. Kontogeorgos ◽  
Maria A. Founti
Keyword(s):  
In Situ Measurement ◽  
Thermal Transmittance ◽  
Lightweight Steel ◽  
New Methods

scholarly journals Displacement Calculation Method on Front Wall of Covered Sheet-Pile Wharf

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Wen-xue Gong ◽  
Li-yan Wang ◽  
Jinsong Li ◽  
Bing-hui Wang
Keyword(s):  
Earth Pressure ◽  
In Situ Measurement ◽  
Front Wall ◽  
Surface Boundary ◽  
Sheet Pile ◽  
Soil Arching ◽  
Theoretical Derivation ◽  
Measurement Results ◽  
Stress And Deformation

Covered sheet-pile wharves are widely used in port engineering, water conservancy, and civil engineering. This paper is based on the theory of earth pressure and the soil arching effect. According to the stress and deformation characteristics of the covered sheet-pile wharf, the formulas used to calculate the force and deformation of the front wall of a covered sheet-pile wharf under static loads are deduced. The accuracy of the theoretical derivation is verified by comparing actual measured stress and deformation data of Jingtang Port 32#. The comparison shows that when calculating the displacement of the section below the mud surface boundary, the results are in agreement with the in situ data. However, when calculating the displacement of the section above the mud surface boundary, if the anchorage point displacement is ignored because the anchorage point displacement is limited artificially, the calculated tension of the tie rod is relatively large. This leads to a significant decrease in the calculation result of the section above the mud surface boundary, which is very different from actual in situ measurement results. If anchorage point displacement is considered, the calculated tension of the tie rod is more accurate, and the calculation results of the front wall displacement are very close to in situ measurement results because the anchorage point displacement is assumed scientifically.

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