•A method to assess thermal bridging heat loss using the outdoor ITT is developed.•The ITT approach is compared with hot box measurements and numerical predictions.•The wind velocity impact on ...thermal bridging is quantified.•Adjusting procedure for the Ψ-value measured at different wind velocities is developed.•This procedure allows measured and standard Ψ-value comparison.
Improving the thermal performance of the existing building stock is essential to significantly reduce the overall energy consumption in the building sector. A key objective is the retrofitting of the existing building envelope. A necessary first step in the building envelope optimization process is the assessment of its actual thermal performance. This assessment should be repeated after retrofitting to clearly define the improvements that were made and the heat loss reduction that was achieved. In this study, an efficient, non-destructive, in-situ measurement method, based on an outdoor infrared thermographic survey, is developed to determine the thermal bridging performance. As wind velocity significantly influences the heat losses through the building envelope, this study includes quantification of the wind velocity impact on the Ψ-value. This was assessed by undertaking ITT of the same thermal bridge at various wind velocities, in a controlled environment, in a hot box device. The results showed that the Ψ-value is highly dependent on wind velocity so that measurement of the Ψ-value taken at different wind conditions cannot be directly compared. An adjustment procedure is proposed that can be used to convert the Ψ-value measured at any wind velocity to a standard value corresponding to a velocity of 4m/s. From a practical point of view, this adjustment procedure makes the methodology widely applicable.
•Quantitative ITT methodology to obtain the thermal bridge heat flow rate in buildings presented.•Methodology suitable for determining Ψ-values of any existing building envelope.•Excellent agreement ...found while testing the methodology in the hot box device.•Relative deviation in Ψ-values from ITT and from hot box measurements varied from −5% to −36%.
A key aspect in assessing the thermal standard of building envelopes is the quantification of the heat loss though thermal bridging, which can be expressed in terms of the linear thermal transmittance Ψ. Values of Ψ may be obtained from tabulated values for standard building details, from numerical modelling or from measurement. Where the internal structure of the building envelope is unknown, which is very often the case, measurement is the only option. This study shows how the infrared thermography technique (ITT) can be used as a non-invasive and easy-to-use method to provide quantitative measures of the actual thermal bridging performance. The novelty of this approach includes evaluation of the actual heat flow rate caused by thermal bridge qTB and Ψ-value by means of the ITT solely, without any supporting methods. Another important aspect of the methodology is that it accounts for the correlation between the surface temperature and the convective and radiative heat transfer coefficients. Values for these coefficients are assessed for the whole range of the surface temperatures recorded on the thermogram resulting in improve accuracy. The qTB and Ψ-value calculated using the presented methodology fully mirrors the real thermal performance of the thermal bridge. The methodology has been tested under laboratory conditions in a steady state in a hot box with excellent agreement.
•Using infrared thermography, multiple thermal bridging heat loss can be easily estimated.•Installed window heat loss assessed by infrared thermography.•Results validated with hot box ...measurements.•Thermographic analysis results in good agreement with FE heat transfer and CFD simulations.
A major contribution to the global trend in reducing energy consumption can be made by improving the thermal performance of buildings. Minimization of heat loss via the building envelope is key to maximizing building energy efficiency. The building envelope contains different types of thermal bridging that must be accounted for while assessing the overall building envelope thermal performance. Multiple thermal bridges commonly occur and the distance between them determines the degree to which they interact thermally. To avoid overestimation of the linear thermal transmittance, it is important to account for interaction effects. Complex multiple thermal bridging occurs in window systems. The thermal performance of windows depends not only on the window performance itself but also on its installation into the wall. This study demonstrates an application of the quantitative infrared thermography technique to evaluate the heat lost via multiple thermal bridging. It is shown that using this methodology, the heat loss via multiple thermal bridges can be easily estimated in an existing building envelope, without any knowledge of its internal structure or material properties. For windows, it is demonstrated that jointly assessing the additional heat loss through the window and due to the installation of the window into the wall is a practical way to determine the actual heat loss caused by the presence of a window. A window thermal transmittance or M-value is introduced to quantify the total additional heat loss through the building element due to the presence of the window. The methodology was validated against experimental measurements taken on different specimens in a hot box device. Results from the thermographic analysis also co-related well with results from finite element heat transfer and computational fluid dynamics simulations.
•CFD simulations of PVC window frames are performed.•Insulation insertions into air gaps in PVC frame are proposed.•Low-emmissivity coatings on air gaps in PVC frame are proposed.•Measurements of ...frame thermal transmittance were undertaken.•EnergyPlus simulations of building’s energy use with different window frames were performed.
In this paper, two ways to improve the PVC window frame thermal transmittance without frame geometrical dimension and material variations are presented. The first variation considered relies on inserting polyurethane foam into the air gaps. The second variation counts on low-emissivity coating on PVC surfaces in the frame air gaps. To investigate these modifications two-dimensional CFD simulations of PVC window frames were used which then were validated by measurements performed in a calorimetric chamber. A hot box methodology was implemented for the measurements. The experimental work was focused on verification of simulation results of modeled frame thermal transmittances. A calorimetric chamber was used, consisting of a metering box, simulating indoor conditions (warm side), and a climate box, simulating outdoor conditions (cold side). It was concluded that the air gap filling with polyurethane foam in window frames can reduce window frame thermal transmittance by about 27% while covering PVC surfaces with low-emissivity coating can reduce window frame thermal transmittance by about 28%. These variations do not change the frame geometry or its total thickness.
To answer the question what would be the expected impact of proposed frame variations on annual energy demand of different types of buildings additional simulations of two buildings with a DesignBuilder with EnergyPlus engine software were performed for a set of different climatic conditions.
•Dynamic thermal properties of building components are experimentally investigated with procedures validated by the theoretical analysis.•Two different approaches of unsteady-state thermal ...solicitations are tested in two hot box apparatuses.•The impulsive thermal solicitation results faster but less accurate then the sinusoidal thermal driving force.•The possibility of hosting infrared cameras inside hot box devices allows detailed analyses of building components.
The envelope thermal behaviour in dynamic conditions is becoming essential to assess the whole year energy performance of buildings. International Standards describe in detail the theoretical approach, but few examples of experimental analyses and procedures exist to determine the performance of materials and components in unsteady-state conditions. The work is aimed at filling this vacancy, describing a modification of hot box devices, which are generally designed for stationary measurements, but they could be successfully used also for time-dependent investigations. Two different methods are proposed: a hot box system where one-day period sinusoidal solicitations in terms of temperature and heat flow are imposed, and another type of boundary condition, with a faster impulsive thermal driving force. The former showed a good agreement with the expected theoretical results; the latter proved also suitable but suffered a lower accuracy, being characterised in turn by a significant reduction of the measurement time. It is also showed that hot boxes allow also more detailed investigations, such as infrared thermography imaging, to better analyse the thermal performance of the tested samples.
•A wall with variable thermophysical properties is proposed;•The wall thermal transmittance may be reduced up to ten times in a few minutes;•An yearly energy saving up to 50% can be reached with ...adaptive walls in buildings;•The most effective performance is found in moderate and hot climate zones.
A new wall characterised by variable thermophysical properties is presented; this characteristic is obtained through the drowning of pipes on the inner and outer surfaces of the wall, hosting a heat-carrying fluid pushed by a pump, at the aim of transporting heat in the direction of the thickness of the wall, when desired. The concept of the environment-adaptive wall is described and numerical simulations are implemented to assess the performance of the system, which proved itself particularly quick to react to external solicitations. Beyond the stand-alone computational fluid dynamic analysis, the proposed solution is also tested in an entire construction by means of a dynamic simulation software, in different cities. Results showed that the better performance is obtained in moderate climate environments, especially in the hot season: a reduction even higher than the 50% of the heating and cooling envelope energy losses and gains can be reached, respect to a reference building realised with local state-of the-art criteria and subjected to the same operating conditions. The proposed system showed itself less incisive in cold climates.
•There is little information about calculation procedure of thermal transmittance for reversed glazing.•The CFD simulations through the glazing under different angles are performed.•Measurements of ...glazing under different angles in a test stand were undertaken.•Reasonable agreement between calculation and measurement results is achieved.•The amendments to EN 673 and ISO 15099 Nusselt number calculation procedure are proposed.
Fenestration systems are important elements of building facades. Although there are fenestrations placed at different angles in facades, not only vertical and roof glazing, there is little information about calculating procedures of thermal resistance and thermal transmittance for reversed glazing in which heat flows in a downward direction. The aim of this paper is to propose some amendments to EN 673–Glass in building – Determination of thermal transmittance (U value) – Calculation method 1 as well as to ISO 15099 – Thermal performance of Windows – Detailed calculations 2 to improve calculation accuracy for glazing under downward heat flow direction. In the paper CFD modeling of glazing thermal transmittance is presented. CFD calculated data were then validated by measurements performed in a calorimetric chamber in a test stand prepared for thermal transmittance measurements under different glazing angles resulting in a downward heat flow direction. Measurement data are then compared to simulation results. After achieving satisfactory agreement, some additional simulation results are presented and some amendments to glazing thermal resistance calculation procedure given in EN 673 and ISO 15099 standards are proposed.
•A model of unsteady heat exchange in light structure rooms is proposed.•Model takes into account radiator capacity and intermittent heating.•Reasonable agreement between calculation and measurement ...results is achieved.•Thermal comfort indices PMV and PPD are evaluated.
Intermittent heating is one of the methods leading to savings in energy consumption. The intermittent heating system can work with reduced power or it can be completely cut off when the rooms are not occupied. At the beginning of the cut-off mode, the radiator remains warm for a specific period of time, due to its thermal capacity. This capacity is not negligible and should be considered for buildings with light or very light structures. This paper outlines a mathematical model of unsteady heat exchange in rooms with light wall structure with intermittent heating. The air heat balance of a given room takes into account the room air capacity, hot water radiator capacity, heat transfer through walls, ceiling, floor and windows as well as air infiltration. Reasonable accuracy between calculation and measurement results has been achieved. With known air and radiant temperatures, air humidity and velocity, thermal comfort indices predicted mean vote (PMV) and predicted percentage of dissatisfied (PPD) were evaluated in order to verify how thermal comfort changes during radiator cut-off mode. The satisfactory convergence between measured and calculated internal air temperatures has been achieved.
Vemurafenib and dabrafenib are BRAF kinase inhibitors (BRAFi) used for the treatment of patients with melanoma carrying the V600E BRAF mutation. However, melanoma cells develop resistance to both ...drugs when used as monotherapy. Therefore, mechanisms of drug resistance are investigated, and new molecular targets are sought that could completely inhibit melanoma progression. Since receptor-interacting protein kinase (RIPK4) probably functions as an oncogene in melanoma and its structure is similar to the BRAF protein, we analyzed the impact of vemurafenib and dabrafenib on RIPK4 in melanomas. The in silico study confirmed the high similarity of BRAF kinase domains to the RIPK4 protein at both the sequence and structural levels and suggests that BRAFi could directly bind to RIPK4 even more strongly than to ATP. Furthermore, BRAFi inhibited ERK1/2 activity and lowered RIPK4 protein levels in BRAF-mutated melanoma cells (A375 and WM266.4), while in wild-type BRAF cells (BLM and LoVo), both inhibitors decreased the level of RIPK4 and enhanced ERK1/2 activity. The phosphorylation of phosphatidylethanolamine binding protein 1 (PEBP1)-a suppressor of the BRAF/MEK/ERK pathway-via RIPK4 observed in pancreatic cancer did not occur in melanoma. Neither downregulation nor upregulation of RIPK4 in BRAF- mutated cells affected PEBP1 levels or the BRAF/MEK/ERK pathway. The downregulation of RIPK4 inhibited cell proliferation and the FAK/AKT pathway, and increased BRAFi efficiency in WM266.4 cells. However, the silencing of RIPK4 did not induce apoptosis or necroptosis. Our study suggests that RIPK4 may be an off-target for BRAF inhibitors.
