•The solar loading was used as thermal stimulus.•Buildings without heating systems in operation were analyzed.•Iterative filtering minimized the influence of the shadows projected on the ...facade.•Sparse principal component thermography was used to detect thermal bridges.•The measurement accuracy improved after the application of the iterative filtering.
The detection of thermal bridges in buildings is one of the key points to be taken into account in energy saving procedures during refurbishment works. Passive infrared thermography (IRT) has been applied for years to detect thermal bridges by referring to the International Organization for Standardization (ISO) 6781:1983. However, the successfulness of this norm is strongly affected by the detection accuracy of the thermal imprint produced on the facade by a conductive material called as “defect” in this work. The drop shadow effect, also produced by the surrounding environment on the facade under inspection, plays indeed an important role during the defect evaluation procedure since it can mask/modify the natural thermal evolution due to diffusion.
Many real-life signals acting in the space physics domain exhibit variations across different temporal scales. This work presents an application of a new multiscale data analysis method, the Iterative Filtering (IF), which allows to describe the multiscale nature of an electromagnetic signal working in the long-wave infrared (LWIR) region. IF appears to be a promising method minimizing the influence of the shadows projected on the facade under inspection; subsequently, it allows the optimization of the detection of thermal bridges via sparse principal component thermography (SPCT) technique. The latter inherits the advantages of PCT allowing more flexibility by introducing a penalization term.
Here is shown how the accuracy of the defect detection increases after the application of the IF mathematical procedure. Results are discussed on the basis of a couple of case studies referring to dissimilar buildings. Finally, a signal-to-noise-ratio (SNR) comparison with raw data is added to the discussion of the results.
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Research on 2D materials originally focused on the highly symmetrical materials like graphene, h‐BN. Recently, 2D materials with low‐symmetry lattice such as PdSe2 have drawn extensive attention, due ...to the interesting layer‐dependent bandgap, promising mechanical properties and excellent thermoelectric performance, etc. In this work, the phonon thermal transport is studied in PdSe2 with a pentagonal fold structure. The thermal conductivity of PdSe2 flakes with different thicknesses ranging from few nanometers to several tens of nanometers is measured through the thermal bridge method, where the thermal conductivity increases from 5.04 W mk−1 for 60 nm PdSe2 to 34.51 W mk−1 for the few‐layer one. The atomistic modelings uncover that with the thickness thinning down, the lattice of PdSe2 becomes contracted and the phonon group velocity is enhanced, leading to the abnormal increase in the thermal conductivity. And the upshift of the optical phonon modes contributes to the increase of the thermal conductivity as well by creating less acoustic phonon scattering as the thickness reduces. This study probes the interesting abnormal thickness‐dependent thermal transport in 2D materials, which promotes the potential thermal management at nanoscale.
The in‐plane phonon thermal transport in PdSe2 flakes with different thicknesses ranging from few nanometers to several tens of nanometers is characterized by the thermal bridge method, where the thermal conductivity increases from 5.04 W mk−1 for 60 nm PdSe2 to 34.51 W mk−1 for the few‐layer one. This work promotes the potential thermal management at nanoscale.
•A measurement method of thermal bridge for vacuum insulation panel was presented.•Model focusing on edge effect to predict thermal bridge was proposed.•Linear and point thermal transmittance were ...used to evaluate thermal bridge.•The thermal conductivity can increase 110% due to thermal bridge.
Vacuum insulation panel, composed of a core material and a barrier, is a very efficient thermal insulation material. Compared with conventional insulation materials, the vacuum insulation panel is proposed to achieve a better insulated performance. However, its thermal conductivity will be seriously increased and insulated performance will be significantly decreased since the additional heat is transferred through the barrier; that is called thermal bridge effect. This paper emphasized on effective thermal conductivity to evaluate the performance of vacuum insulation panel. Two criteria, i.e., the linear and point thermal transmittance are introduced to evaluate the comprehensive performance of vacuum insulation panel. A heat transfer model was used to analyze the thermal bridge. Then, a fast and effective method for measuring thermal bridge is presented, which is supported by numerical simulation analysis. The results indicated that thermal bridge not only could increase with the increasing of the mental foil (main aluminum) thickness, but also could exhibit higher heat losses with the reducing of thickness of the vacuum insulation panel. Overall, the effective thermal conductivity of vacuum insulation panel could increase by 110.8% when the barrier contains 10 μm mental foil and the size of vacuum insulation panel is 300 × 300 × 10 mm3. This research provides a reference for measuring the thermal bridge and could also disclose the quantitative behavior of physical parameters in thermal bridge.
During the design of the external cladding, it is possible to use different materials and compositions. One of these possibilities is also a ventilated facade, which consists of a supporting ...structure, a thermal insulation, a supporting grid, an air gap for ventilation and a cladding layer. The construction of the supporting grid in the ventilated facade must be mechanically anchored into the supporting structure of the external cladding. This mechanical anchoring causes 3-D point thermal bridges in the external cladding itself. Therefore, the aim of this work is to assess and analyze the influence of these 3-D point thermal bridges on transmission heat losses through the external cladding. A Finite Element Mesh analysis has been used for this analysis. Different types of external cladding compositions were modeled in the simulation program, and the effect on the heat transfer coefficient was determined. In addition to the analysis of the existing anchoring systems, an innovative solution has been suggested that is more economical and easier to implement. The results show that the application of anchors and their number impacts significantly on the thermal properties of the envelope. The difference between the anchoring element with a thermal insulation pad and the patented method is minimal. This is a 1.29% difference. The last variant was a proposal (patent) that the anchoring element is only plastic-coated and thus its thermal engineering properties are improved, which is manifested mainly in heat conduction but also from the radiant point of view, as plasticizing the emissivity changes. Compared to the perimeter cladding without the ap-plication of an anchoring element, the heat loss increases by 29.37%. In addition to the energy savings, there are also financial savings. While the plastic pads costs about EUR 0.3, the plastic coating (patent) represents a price of around EUR 0.03. If we had a building with 10,000 m2 of wall area where 6 pieces of anchors per 1 m2 are applied, the savings would be EUR 16,200. Such savings are already significant. The conclusion of this work is that these point thermal bridges have a significant impact on the overall transmission heat loss coefficient and therefore they have overall heat demand and energy demand.
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The energy consumption in buildings contributes substantially to the worldwide energy use and greenhouse gas emissions. One of the crucial elements defining energy consumption is the ...building envelope, which in modern designs includes growing share of fenestration. Due to recent improvements of windows and walls, the thermal bridging effects occurring on their connections, become more significant. Window-to-wall connections appear to be especially important and can contribute up to 40% of the total heat loss caused by thermal bridges in building envelope. Thus, this study is investigating thermal properties of window-to-wall connections. The main scope of the work is to determine the most efficient window position in the window opening regarding minimizing thermal bridging effects. Five different wall constructions are investigated along with two windows with different U-values. The thermal simulation results show that the window position has a crucial impact on the amount of energy loss through the thermal bridges. For each wall type, the most energy-efficient position is found, resulting from detailed analysis of sill, head, and jambs construction details. For some cases placing the window in the most energy-efficient position reduces linear thermal transmittance (LTT) over 50%. Among considered positions, the temperatures on the internal surface of the assemblies are weakly influenced by the window position. Example calculations show that significant share of energy losses from the fenestration presence is caused by thermal bridge occurring on window-to-wall.
•Field measurements verified the numerical simulation of heat transfer of the WFTB.•The effects of the wall and insulation-layer materials on the WFTB were quantified.•The envelope materials had ...synergistic effects on the thermal insulation of the WFTB.•Empirical formulas were provided for assessing the insulation performance of the WFTB.
The amount of heat loss through thermal bridges increases with the improvement of the thermal insulation performance of the building exterior wall, making thermal bridges vulnerable points of thermal insulation. The wall-to-floor thermal bridge (WFTB) takes the most considerable fraction on the building envelope and has the largest heat flux. In this study, we aimed to (1) develop a new method to evaluate the insulation performance of the WFTB, which is easier to implement in engineering, and (2) propose a strategy to reduce heat loss due to the WFTB. The apparent thermal resistance of the WFTB (RTB), which is affected by the thermal resistance of the wall (RW) and the insulation layer (RI), was defined to quantify the effects of the building envelope material on the thermal performance of the WFTB. Numerical simulations and full-scale (1:1) experiments were conducted to investigate the insulation performance of the WFTB under different conditions. The results indicated that RTB increased monotonously with an increase in RI. However, the increase became slower with an increase in RI, indicating that improving the insulation performance of the insulation layer cannot effectively improve RTB when RI is relatively high. Additionally, the changing rate of RTB with respect to RW varied among different RI values, indicating that RW and RI have a synergistic effect on RTB. An empirical formula was obtained for calculating RTB using RW and RI. WFTBs in different buildings can be analyzed using this formula. Suitable insulating materials for optimizing the performance of WFTBs can thus be identified at the design stage for new buildings and the renovation of existing buildings.
•Thermal bridges of the column are numerically simulated in the refrigeration room.•Contribution shares of reinforcement concrete in the column on the cooling loss are discussed.•Optimization method ...of energy-saving heat preservation is proposed to minimize the cooling loss.
Thermal bridges are weakly insulated areas in the envelope of a building that can significantly increase the energy load due to heat dissipation. To improve energy efficiency, a thermal bridge model is established to simulate heat transfer through the column in a refrigeration room. The accuracy of the numerical simulation program is verified by experimental data. A heat preservation method for the column that minimizes the cooling loss is analyzed. The results show that the thermal bridging is mainly due to the steel bar in the column, because the share of the cooling loss attributed to the steel bars is 42.02–55.87%. Moreover, applying heat insulation on the column can provide more energy savings in low-temperature rooms than in high-temperature ones. The most economical thermal insulation method as a function of the height and thickness of the insulation layer is therefore proposed for the low-temperature column. By the optimum method, the amount of heat flux through the whole column section, which includes both reinforced and non-reinforced areas, decreases by 37.34%, and the total cooling loss decreases from 30.23 to 13.66 W, representing a 54.81% reduction. Therefore, a reduction in the cooling loss from thermal bridging is achieved for a low-temperature refrigeration room.
•Thermal performance of TDGS for underground space was investigated.•Additional acrylic separator plate reduces conduction and convection in cavities of TDGS.•Heat transfer coefficient of TDGS varies ...with the position of a separator plate.•Increasing the count of glassing strongly reduces thermal bridge effect and condensation.•These light guides are beneficial for well insulated flat roof with overlying soil.
As an emerging passive daylighting technology, tubular daylight guidance systems (TDGSs) are increasingly used in low-energy buildings. However, TDGS may become a thermal bridge to increase indoor air conditioning load. To avoid an increase in total energy consumption, the thermal analysis of a flat roof section with a TDGS is simulated using CFD in this work. Additionally, the simulation compares the heat transfer performance of a conventional TDGS with eight different designs TDGS that contain additional glass unit. The findings show that TDGS has a thermal bridging effect on an insulated flat roof with overlying soil. The additional glass unit in the middle of the conventional TDGS with diameter 500 mm decreases its overall heat transfer coefficient by 53 %. Further, the same thickness of glass is divided into 4 layers and evenly distributed inside the TDGS with diameter 500 mm, which can reduce the total heat transfer coefficient of the conventional TDGS by 67 %.
An energy-efficient and environmentally conscious bamboo-constructed residential structure was created, comprising bamboo composite panels, steel framework, and mineral wool insulation. To ascertain ...the efficacy of this particular type of wall in enhancing thermal capabilities, the finite element method was employed to analyze the factors influencing the thermal performance of the exterior wall panels, insulation layer, framework, and interior wall panels. A more judicious design and implementation strategy, known as the 3# and 8# combination scheme, was evaluated in practical applications to assess the thermal efficiency of the wall system. The findings indicated that augmenting the thickness of the inner and outer wall panels and insulation layer, reducing the framework thickness, and incorporating wooden framework as a substitute for steel framework within a certain range enhanced the thermal capabilities of bamboo-constructed walls and mitigated the adverse effects of thermal bridges. The thermal performance of the residences employing the newly developed bamboo-constructed walls surpassed that of conventional iron container houses, thereby warranting broader adoption and application in practical projects. These outcomes offer valuable insights for the optimized design of thermal performance in bamboo-constructed walls.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•Study of thermal bridges in a traditional building is performed.•Effects of different agricultural wastes are investigated.•Most critical connection is wall-to-wall connection.•The optimal thickness ...for straw insulation is 3 cm.
High energy use in buildings plays a key role in climate change and air pollution in cities of Iran. In this regard, the use of thermal insulation to reduce energy demand has been proposed as an important solution. Production of thermal insulation made from chemicals consumes high energy and their disposal has high environmental effects. Therefore, the use of agricultural waste due to their abundance in Iran, low energy consumption for production and high renewability rate, seems to be justified as an alternative to chemical-based insulation. Due to the importance of the above issues, in the present work for the first time with the aim of investigating the phenomenon of thermal bridges in traditional buildings of Iran, the ZUB ARGOS software is used to evaluate the effect of 10 different agricultural wastes (cork, cellulose fiber, meadow grass, flax, sheep wool, straw, hemp, cotton, grain granules, and cattail) as thermal insulation on the inside face of the wall, find the optimal thickness of common waste (straw) to remove the phenomenon of thermal bridges and evaluate the effect of the horizontal or vertical direction of straw fibers to the heat transfer path in the city of Yazd located in the hot and dry climate of Iran. The results of the current situation simulations showed that the thermal bridge phenomenon occurs in the building under study and the most critical connection with f = 0.48 is related to the wall-to-wall connection. Among the agricultural wastes, cork is the most suitable insulation with fmin = 0.76. The results of the 10 wastes investigation also showed that the wall-to-wall connection and the window lintel connection are according to the order the most critical and safest connections for creating a thermal bridge in the building under study. Due to the abundance of straw waste in the studied climate, this insulation was selected to optimize the current situation. The results showed that the placement of straw fibers perpendicular to the heat flow compared to its horizontal direction has a maximum advantage of 4.35%. The results showed that the optimal thickness for straw insulation is 3 cm, which means that no thermal bridge in connections occurs and cork is the most suitable insulation among the agricultural wastes studied.
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