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Buildings contribute to nearly 30% of global carbon dioxide emissions, making a significant impact on climate change. Despite advanced design methods, such as those based on dynamic simulation tools, a significant discrepancy exists between designed and actual performance. This so-called performance gap occurs as a result of many factors, including the discrepancies between theoretical properties of building materials and properties of the same materials in buildings in use, reflected in the physics properties of the entire building. There are several different ways in which building physics properties and the underlying properties of materials can be established: a co-heating test, which measures the overall heat loss coefficient of the building; a dynamic heating test, which, in addition to the overall heat loss coefficient, also measures the effective thermal capacitance and the time constant of the building; and a simulation of the dynamic heating test with a calibrated simulation model, which establishes the same three properties in a non-disruptive way in comparison with the actual physical tests. This article introduces a method of measuring building physics properties through actual and simulated dynamic heating tests. It gives insights into the properties of building materials in use and it documents significant discrepancies between theoretical and measured properties. It introduces a quality assurance method for building construction and retrofit projects, and it explains the application of results on energy efficiency improvements in building design and control. It calls for re-examination of material properties data and for increased safety margins in order to make significant improvements in building energy efficiency.

The authors analyze global climate model predictions of soil temperature [from the Coupled Model Intercomparison Project phase 5 (CMIP5) database] to assess the models’ representation of current-climate soil thermal dynamics and their predictions of permafrost thaw during the twenty-first century. The authors compare the models’ predictions with observations of active layer thickness, air temperature, and soil temperature and with theoretically expected relationships between active layer thickness and air temperature annual mean- and seasonal-cycle amplitude. Models show a wide range of current permafrost areas, active layer statistics (cumulative distributions, correlations with mean annual air temperature, and amplitude of seasonal air temperature cycle), and ability to accurately model the coupling between soil and air temperatures at high latitudes. Many of the between-model differences can be traced to differences in the coupling between either near-surface air and shallow soil temperatures or shallow and deeper (1 m) soil temperatures, which in turn reflect differences in snow physics and soil hydrology. The models are compared with observational datasets to benchmark several aspects of the permafrost-relevant physics of the models. The CMIP5 models following multiple representative concentration pathways (RCP) show a wide range of predictions for permafrost loss: 2%–66% for RCP2.6, 15%–87% for RCP4.5, and 30%–99% for RCP8.5. Normalizing the amount of permafrost loss by the amount of high-latitude warming in the RCP4.5 scenario, the models predict an absolute loss of 1.6 ± 0.7 million km² permafrost per 1°C high-latitude warming, or a fractional loss of 6%–29% °C−1.

The effect of thermal treatment on several physical properties and the tensile strength of Laurentian granite (LG) are measured in this study. Brazilian disc LG specimens are treated at temperatures of up to 850 °C. The physical properties such as grain density, relative volume change per degree, and P-wave velocity are investigated under the effect of heat treatment. The results indicate that both the density and the P-wave velocity decrease with the increase in heating temperature. However, the relative volume change per degree is not sensitive below 450 °C, while a remarkable increase appears from 450 to 850 °C. All cases are explained by the increase in both number and width of the thermally induced microcracks with the heating temperature. Brazilian tests are carried out statically with an MTS hydraulic servo-control testing system and dynamically with a modified split Hopkinson pressure bar (SHPB) system to measure both static and dynamic tensile strength of LG. The relationship between the tensile strength and treatment temperatures shows that static tensile strength decreases with temperature while the dynamic tensile strength first increases and then decreases with a linear increase in the loading rate. However, the increase in dynamic tensile strength with treatment temperatures from 25 to 100 °C is due to slight dilation of the grain boundaries as the initial thermal action, which leads to compaction of rock. When the treatment temperature rises above 450 °C, the quartz phase transition results in increased size of microcracks due to the differential expansion between the quartz grains and other minerals, which is the main cause of the sharp reduction in tensile strength.

Heat pumps represent a key factor in the electrification of heating and cooling and are crucial for the energy transition towards low-carbon systems. The adoption of innovative solutions, such as multi-source configurations and low-GWP refrigerants like carbon dioxide also improve sustainability and system efficiency. The studied system is a dual-source (air/sun), reversible carbon-dioxide heat pump installed at the ENEA Research Center in Casaccia. The prototype, with about 10 kW of heating capacity, is designed to provide chilled water during the summer season and hot water for both space heating in winter and sanitary water production and integrates two strings of five photovoltaic thermal hybrid solar panels to both produce electricity and assist the evaporation process. This paper presents dynamic heating-mode tests for space heating in climatic zone D, focusing on the cooling effect of the panels and its impact on their performance. Steady-state tests validated the dynamic tests findings, showing an average improvement in electrical efficiency of 8.06%. Finally, thermal imaging on panel surfaces with the heat pump off and on revealed a surface temperature drop from 50°C to 25°C corresponding to roughly 0.52% efficiency gain per degree Celsius reduction.

Fused deposition modeling (FDM), an economical additive manufacturing (AM) technique, is widely used for extruding thermoplastic filaments. Acrylonitrile butadiene styrene (ABS) is a widely used polymer for FDM technique due to its inexpensive cost, strong impact strength, great durability, and intriguing uses. ABS materials are used for interior parts of automotive applications, drug-delivery systems, tracheal tubes, valves for ventilators, and medical masks. Nonetheless, shrinkage and warping are the primary weaknesses of ABS during the FDM process, affecting the dimensional stability of printed parts. In this context, a patent-pending radiant heating system has been developed to improve the overall performance of printed parts. This study aimed to evaluate the effect of in situ thermal treatment on the interlayer adhesion and mechanical properties of printed ABS parts. The thermal treatment was carried out on a radiant heating system at 240 °C and a printing speed of 35 mm·s −1 . The physical and mechanical properties of ABS parts printed with and without radiant heating were then characterized. Various techniques, including tensile tests, X-ray microtomography (µ-CT), optical profilometry (OP), atomic force microscopy (AFM), and dynamic mechanical analysis (DMA), were conducted to investigate mechanical, microstructural, and topological properties of printed ABS parts. The results show that treated samples exhibit better interlayer adhesion than untreated ones. In addition, the treated samples had a lower porosity (1.6%) than the untreated samples (3%). Furthermore, the tensile strength, elastic modulus, and elongation at break of treated samples increased by 62%, 6%, and 110%, respectively, compared to untreated ones.

The high cooling rate and temperature gradient caused by the rapid heating and cooling characteristics of laser welding (LW) leads to excessive thermal stress and even cracks in welded joints. In order to solve these problems, a dynamic preheating method that uses hybrid laser arc welding to add an auxiliary heat source (arc) to LW was proposed. The finite element model was deployed to investigate the effect of dynamic preheating on the thermal behavior of LW. The accuracy of the heat transfer model was verified experimentally. Hardness and tensile testing of the welded joint were conducted. The results show that using the appropriate current leads to a significantly reduced cooling rate and temperature gradient, which are conducive to improving the hardness and mechanical properties of welded joints. The yield strength of welded joints with a 20 A current for dynamic preheating is increased from 477.0 to 564.3 MPa compared with that of LW. Therefore, the use of dynamic preheating to reduce the temperature gradient is helpful in reducing thermal stress and improving the tensile properties of the joint. These results can provide new ideas for welding processes.

For thermoviscoelastic behaviors limited to ultrashort laser pulse technologies, the Fourier’s heat conduction law may fail; meanwhile, new models, e.g., the fractional-order heat conduction model, have been developed to modify Fourier’s law. Furthermore, it is found that the fractional-order viscoelastic models fit well with the experimental data from relaxation tests. Meanwhile, with the miniaturization of devices, the size-dependent effect on elastic deformation is becoming increasingly important. This paper addresses the transient thermoviscoelastic response of a polymer micro-rod subjected to an ultrashort laser pulse heating including the simultaneous effects of the fractional order parameter and the nonlocal parameter for the first time. The governing equations are obtained and solved by the Laplace transform method. In calculation, the influences of the magnitude of the laser intensity, the fractional-order parameter and the nonlocal parameter on the variation of the considered variables are analyzed and discussed in detail. It is hoped that the obtained results will be helpful in designing the viscoelastic micro-structures induced by a short-pulse laser heating.

Theoretical, observational, and modeling studies have established an important role for latent heating in midlatitude cyclone development. Models simulate some contribution from condensational heating to cyclogenesis, even with relatively coarse grid spacing (on the order of 100 km). Our goal is to more accurately assess the diabatic contribution to storm-track dynamics and cyclogenesis while bridging the gap between climate modeling and synoptic dynamics. This study uses Weather Research and Forecasting model (WRF) simulations with 120- and 20-km grid spacing to demonstrate the importance of resolving additional mesoscale features that are associated with intense precipitation and latent heat release within extratropical cyclones. Sensitivity to resolution is demonstrated first with a case study, followed by analyses of 10 simulated winters over the North Atlantic storm track. Potential vorticity diagnostics are employed to isolate the influences of latent heating on storm dynamics, and terms in the Lorenz energy cycle are analyzed to determine the resulting influences on the storm track. The authors find that the intensities of individual storms and their aggregate behavior in the storm track are strongly sensitive to horizontal resolution. An enhanced positive feedback between cyclone intensification and latent heat release is seen at higher resolution, resulting in a systematic increase in eddy intensity and a stronger storm track relative to the coarser simulations. These results have implications for general circulation models and their projections of climate change.

We propose an extension of the bivariate nonparametric Diks–Panchenko Granger non-causality test to multivariate settings. We first show that the asymptotic theory for the bivariate test fails to apply to the multivariate case, because the kernel density estimator bias and variance cannot both tend to zero at a sufficiently fast rate. To overcome this difficulty we propose to reduce the order of the bias by applying data sharpening prior to calculating the test statistic. We derive the asymptotic properties of the ‘sharpened’ test statistic and investigate its performance numerically. We conclude with an empirical application to the US grain market, using the price of futures on heating degree days as an additional conditioning variable.

Several studies have been conducted in the Very High Cycle Fatigue (VHCF) regime on Carbon Fiber Reinforced Polymers (CFRP) in search of their fatigue limit beyond their typical service life, which is itself in the order of 108 loading cycles. The ultrasonic fatigue test (UFT) method has been recently gaining attention for conducting fatigue experiments up to 109 loading cycles. This can be attributed to the reduction of testing time, as the testing facility operates at a cyclic frequency of 20 kHz. The fatigue loading in UFT is usually performed in a pulse–pause sequence to avoid specimen heating and undesirable thermal effects. For this study, the pulse–pause combination of the UFT methodology was explored and its influence on the self-heating behavior of the CFRP material was analyzed. This was realized by monitoring the temperature evolution in the CFRP specimens at different pulse–pause combinations and correlating it with their final damage morphologies. From the obtained results, it is concluded that the specimen heating phenomenon depends on several variables such as cyclic loading amplitude, the pulse–pause combination, and the damage state of the material. Finally, it is proposed that the test procedure, as well as the testing time, can be further optimized by designing the experiments based on the self-heating characteristic of the composite and the glass transition temperature (Tg) of the polymer matrix.