Search Results (327)

The fire performance of ventilated facade systems incorporating combustible insulation remains a critical issue in contemporary building design. This study presents a full-scale natural-fire test of a ventilated, rendered facade system containing 150 mm expanded polystyrene (EPS) insulation, conducted in accordance with the DIN 4102-20 methodology. Temperature measurements were recorded at key facade locations via K-type thermocouples, and flame spread, materials melting, and degradation were documented through visual observations. The combustion chamber reached a peak temperature of 912 °C, while the thermocouple located above the opening recorded a maximum temperature of 786 °C. No sustained flaming or debris above the 3.5 m height limit was observed, yet significant internal EPS melting occurred throughout the cavity. These findings underscore the potency of the “chimney effect” in ventilated cavities, highlight the limitations of the current acceptance criteria, and provide evidence relevant to ongoing efforts to develop more coherent approaches to facade fire-safety assessment. Full article

Background/Objectives: This study compared the hemodynamic performance of fenestrated (FEVAR), branched (BEVAR), and chimney endovascular aortic aneurysm repair (chEVAR) in patients with complex aortic aneurysms. Methods: The pre- (native) and post-endovascular repair (endograft-defined) blood lumen was reconstructed from computed tomography angiographies of nine (9) elective patients treated with FEVAR (n = 3), BEVAR (n = 3), and chEVAR (n = 3). Computational fluid dynamics (CFD) simulations obtained blood flow properties. Velocity magnitude, wall shear stress (WSS), time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT), and local normalized helicity (LNH) were computed at peak systole and mid-diastole. The hemodynamic data were statistically analyzed to evaluate correlations between FEVAR, BEVAR, and chEVAR, focusing on targeted visceral arteries. Results: Only slight differences were observed regarding RRT, OSI, and TAWSS between FEVAR and BEVAR, whereas the chEVAR group demonstrated a marked deviation from both. In FEVAR, the postoperative helical flow structures appeared more compact, while in BEVAR they were more developed and exhibited a more rotational configuration. The LNH of the visceral vessel patterns exhibited similar qualitative features across groups. Regarding TAWSS, higher values were found in BEVAR, whereas chEVAR showed the lowest. Conclusions: FEVAR, BEVAR, and chEVAR improved postoperative blood flow characteristics toward near-physiological conditions, reducing undesired flow patterns and recirculation zones. FEVAR showed more stable visceral flow, and BEVAR demonstrated higher flow rates and fewer recirculation zones, while chEVAR exhibited more streamlined visceral artery flow with reduced regurgitation at bridging stent entries. Despite variations, all approaches effectively preserved visceral artery perfusion. Full article

Numerical results are presented for a morphology fitted to a passive solar chimney attached to a room coupled with an earth-air heat exchanger. The effects of the variable thermophysical properties of air are included in the modelling. The considered operating mode is room cooling (summer ventilation) by means of an incoming airstream drawn from the soil at a temperature lower than that of the ambient. Buoyancy is assumed to be the only driving force acting on the fluid. A wide range of irradiance over the solar chimney walls, from 10 to 1000 W/m² (Rayleigh number based on the glazing wall from 1.77 × 10¹¹ to 1.77 × 10¹⁴), is analyzed. The impact of the incoming airstream temperature on the overall dynamic and thermal behavior of the system is studied. The induced mass-flow rate and average Nusselt number are presented as a function of relevant parameters for evaluating the passive device performance. The results reveal a strong influence of temperature and the position of the incoming cool airstream on room cooling. Some opposite effects on the relevant parameters are detected, but a sizeable increase in ventilation within the room for the middle and upper positions of the incoming duct is highlighted. Full article

Small combustion installations (SCIs) burning solid fuels remain a major source of particulate matter (PM) emissions responsible for winter smog episodes in many European regions. This study aimed to develop and validate low-cost, micro-scale electrostatic precipitators (ESPs) suitable for retrofitting residential SCIs, and to quantify their PM removal performance under both controlled laboratory conditions and real-life field operation. Two ESP variants were designed and prototyped: (i) a tubular in-line ESP for installation at the boiler flue outlet and (ii) a disk (chimney-bypass) ESP mounted at the chimney outlet, with low energy demand. PM concentrations upstream and downstream of the ESPs were measured using standardized gravimetric, isokinetic sampling with recalculation to reference conditions, and the overall dedusting efficiency was determined from inlet/outlet concentrations. Laboratory testing showed that the micro-scale ESPs can achieve high dedusting efficiencies of approximately 90% under stabilized nominal-load operation. Field trials of the disk ESP in households and small residential buildings confirmed robust performance, with dedusting efficiencies of 70–82% under unsupervised user operation. In most cases, outlet PM concentrations were reduced below applicable Ecodesign thresholds. The results confirm that micro-scale ESPs are a technically feasible and effective “end-of-pipe” option for reducing short-stack PM emissions from solid-fuel heating, offering immediate air quality benefits where appliance replacement or fuel switching is limited by cost or practical constraints. This paper discusses the latest advancements in reducing PM emissions from SCIs. It introduces a prototype design for two types of micro-scale electrostatic precipitators (ESPs) that can be integrated into SCIs that burn solid fuels. The proposed technical solution utilizes an electrostatic method to effectively remove PM from flue gases. An established industrial technology has been adapted to meet the specific technical, economic, and safety needs of residential applications. The paper compares two design variants with a novel self-cleaning mechanism through laboratory testing and presents results from field trials. Findings confirm ESPs can substantially reduce PM emissions from SCIs. Full article

This systematic review synthesizes passive and passive-first cooling strategies for greenhouses in hot–arid climates, organizing evidence across four domains: Airflow & Ventilation, Shading & Radiative Control, Thermal Storage & Ground Coupling, and Structural Design & Geometry. Drawing on the project corpus, we analyze 10–13 distinct techniques including ridge and side natural ventilation, windcatchers and solar chimneys, external shade nets, NIR-selective and transparent radiative-cooling films, and dynamic PV shading; earth-to-air heat exchangers (EAHE/GAHT), rock-bed sensible storage, phase-change materials (PCMs), and sunken or buried envelopes; as well as roof slope and shape, span number, and orientation. Across studies, cooling outcomes are reported as peak or daytime indoor air temperature reductions, defined relative either to outdoor conditions or to a control greenhouse, with the reference frame and temporal aggregation specified in the synthesis. Typical outcomes include ≈3–7 °C daytime reduction for optimized ventilation, ≈2–4 °C for shading and spectral covers while preserving PAR, ≈5–7 °C intake cooling for EAHE with winter pre-heating, and up to ≈14 °C peak attenuation for rock-bed storage under favorable conditions. Structural choices consistently amplify these effects by sustaining pressure head and limiting thermal heterogeneity. Performance is strongly context-dependent—governed by wind regime, diurnal amplitude, dust and UV exposure, and crop-specific light and temperature thresholds—and the most robust results arise from stacked, site-specific designs that combine skin-level radiative rejection, buoyancy-supportive geometry, and ground or latent buffering with minimal active backup. Smart controllers that modulate vents, shading, and targeted fogging or fans based on VPD or temperature differentials improve stability and reduce water and energy use by engaging actuation only when passive capacity is exceeded. We recommend standardized composite metrics encompassing temperature moderation, humidity stability, PAR availability, and water and energy use per unit yield to enable fair cross-study comparison, multi-season validation, and policy adoption. Collectively, the synthesized techniques provide a practical palette for improved greenhouse climate management under hot and arid conditions. Full article

The remote monitoring and quantification of industrial gas emissions, such as sulfur dioxide (SO₂), are critical for environmental protection. This research demonstrates an integrated methodology for estimating SO₂ emission rates (kg/s) from an industrial chimney using passive Fourier transform infrared (FTIR) spectroscopy combined with atmospheric dispersion modeling. Infrared spectra were acquired at a stand-off distance of 570 m within the 7–14 $\mathsf{\mu }$m spectral range at a resolution of 4 cm⁻¹. Path-integrated SO₂ concentrations were determined through cross-sectional scanning of the gas plume. To translate these optical measurements into an emission rate, the atmospheric dispersion of the plume was modeled using the Pasquill–Briggs approach, incorporating source parameters and meteorological data. Over two experimental series, the calculated average SO₂ emission rates were 15 kg/s and 22 kg/s. While passive FTIR spectroscopy has long been applied to remote gas detection, this work demonstrates a consolidated framework for retrieving industrial emission rates from stand-off, line-integrated measurements under real industrial conditions. The proposed approach fills a niche between local in-stack measurements and large-scale remote sensing systems, which contributes to the development of flexible ways to monitor industrial emissions. Full article

This study investigates the dispersion and condensation behavior of tritiated water vapor released into the atmosphere using moist air as a carrier, with an emphasis on safety optimization for nuclear power plant effluent discharge. A coupled heat and mass transfer model was developed and implemented in CFD simulations to analyze the evolution of temperature and relative humidity during the mixing of exhaust moist air with ambient air. The effects of key atmospheric and operational parameters—including the ambient wind speed, turbulence intensity, ambient temperature, relative humidity, and exhaust velocity—were systematically examined. The results indicate that the temperature difference between the exhaust gas and ambient air is the primary factor governing condensation risk. Low wind speeds and weak turbulence favor near-field humidity accumulation, while higher wind speeds and turbulence intensities enhance mixing and dilution, thereby reducing local humidity peaks but extending the downwind impact range. Increasing exhaust velocity strengthens plume rise and long-range transport due to enhanced momentum and latent heat release, mitigating accumulation near the chimney outlet. Furthermore, high ambient temperatures significantly increase the air’s moisture-holding capacity, allowing higher exhaust humidity without inducing condensation. Full article

The International Agreement on the Carriage of Perishable Foodstuffs and on the Special Equipment to Be Used for Such Carriage (usually known as ATP Treaty) defines a standardized isothermal test for qualifying refrigerated containers, but its current protocol is lengthy, costly and lacks scientific justification. This paper presents a combined theoretical and experimental study aimed at optimizing this procedure. First, a heat-transfer framework based on transient conduction and thermal diffusivity is developed to estimate stabilization times using dimensionless criteria. Then, extensive experimental tests on ATP containers validate these predictions and reveal additional phenomena such as air leakage and chimney effects. Based on these findings, a revised protocol is proposed that reduces the test duration from more than 18 h to approximately 2 h while preserving the thermal stabilization conditions required by ATP. Experimental results show that the uncertainty in the determination of the global heat-transfer coefficient K is reduced from about 2–$2.3\%$ in the classical ATP procedure to roughly $0.7$–$1.0\%$ with the new protocol. In addition, the method suppresses secondary physical effects—such as chimney-driven air leakage and latent-heat losses due to water evaporation—thus improving the physical representativeness of the measured K value. The proposed accelerated protocol offers a scientifically grounded, cost-effective alternative for future ATP standards. Full article

Background: Midaortic Syndrome (MAS) is a rare vascular condition characterized by segmental narrowing of the thoracic and abdominal aorta, often involving ostial narrowing of the renal or visceral arteries. While open surgical repair has been the standard treatment, it carries significant morbidity, especially in high-risk patients. Endovascular techniques, including the Chimney approach, provide a minimally invasive alternative to preserve and reestablish both aortic and branch vessel perfusion. This study evaluates the feasibility, safety, and early and midterm outcomes of the Chimney technique used in a cohort of patients with MAS. Methods: Between 2019 and 2025, 9 patients with MAS and branch vessel involvement underwent endovascular repair using the Chimney technique at Brüderklinikum Julia Lanz Hospital in the Mannheim Teaching Hospital of Heidelberg University. Pre-procedural planning was based on computed tomography angiography. Technical success, peri-procedural complications, changes in blood pressure, renal function, and target-vessel stent patency were monitored. Patients were followed over a median of 3 years (range, 0.08–6 years). Results: Nine patients (mean age 77.2 ± 8.7 years; 66.6% female) underwent endovascular repair for midaortic syndrome. All patients were unfit for open surgery. Comorbidities included hypertension (100%), coronary artery disease (100%), and chronic kidney disease (77.7%). Technical success and target-vessel patency were 100%, with no intraoperative deaths, impairment of renal function, or 30-day mortality. One patient (11.1%) developed an access-site hematoma, which was managed conservatively. Median hospital stay was 6 days. During a median 3-year follow-up (range 1 month–6 years), all chimney stents remained patent, patients experienced durable symptom relief, blood pressure improvement, and freedom from reintervention. Conclusions: The Chimney technique offers a safe and effective endovascular option for high-risk patients with Midaortic Syndrome, achieving high technical success, preserved branch-vessel patency, and improvement of symptoms. Larger studies with longer follow-up are warranted to confirm durability and optimize patient selection for this technique. Full article

This study provides a comprehensive analysis of the fire hazards associated with Building-Integrated Photovoltaics (BIPV), using Aluminum Composite Panels (ACP) as a benchmark. Large-scale fire tests, modified from ISO 13785-1, were conducted on vertically installed BIPV modules to observe their fire behavior under conditions simulating a severe fire. The experimental process involved measuring key fire performance indicators, leading to the identification of a cascading failure mechanism. The BIPV modules demonstrated a peak Heat Release Rate (HRR) up to hi times higher (max. 898 kW) and smoke production nearly 10 times greater than the ACP baseline. The analysis reveals a distinct, multi-stage failure sequence that defines the systemic fire hazard of BIPV. Initially, a phenomenon strongly indicative of a chimney effect within the rear air cavity accelerates concealed fire spread. This rapid heating induces thermal stress, leading to extensive specimen damage termed cracking. This cracking event acts as a critical turning point, triggering a rapid release of trapped pyrolyzates and driving the fire to its peak intensity. This chain of events constitutes a unique hazard signature not observed in conventional cladding. The findings conclude that the fire risk of BIPV is a systemic issue, challenging the adequacy of component-level testing and highlighting the need for safety standards that assess the façade as a complete assembly. Full article

Pararenal abdominal aortic aneurysm/pseudoaneurysms (PAAA/PAAP) are rare, high-risk complex aortic lesions involving the renal arteries. Management includes open surgical repair (OSR), endovascular aortic repair (EVAR), or hybrid repair, each with specific advantages and limitations. A review of the literature was performed to assess treatment strategies and outcomes for PAAA and PAAP. A PubMed search using relevant MeSH terms identified 184 articles published in the last five years. After applying inclusion and exclusion criteria, 34 studies comprising 6460 patients with complex AAA/AAP were included for analysis. Treatment strategies were predominantly endovascular (79.4%), followed by open (5.8%) and hybrid approaches (2.9%) (11.7% have used EVAR or OSR in the same study). To emphasize difficulties in the management of this pathology, a case report of a large PAAP involving both renal arteries and occluded celiac trunk with retrograde flow from patent superior mesenteric artery (SMA) is presented. Given the complex anatomy and high surgical risk, hybrid treatment was chosen consisting of bilateral ilio-renal Dacron bypasses followed by ChEVAR (chimney stenting of the SMA), with favorable postoperative recovery. The management of PAAP requires an individualized, anatomy- and risk-adapted approach. Open surgical repair remains preferable for younger, low-risk patients for superior long-term durability, whereas endovascular repair offers lower perioperative morbidity in high-risk cohorts. Optimal outcomes are dependent on high-volume centers with multidisciplinary expertise. Full article

Dynamic wind-induced vibrations of structures will cause cyclic stresses in structural elements, potentially leading to fatigue damage accumulation or structural failure. Existing research on wind-induced fatigue mainly focuses on tower and large-span steel structures, such as chimneys, signal towers, transmission towers, long-span bridges, and wind turbines. However, existing studies on wind-induced fatigue damage in tall steel buildings remain limited. To determine whether and under what conditions wind-induced fatigue damage needs to be considered in tall steel structures, this study investigates wind-induced fatigue failure through wind tunnel tests and numerical simulations. Specifically, six real tall steel buildings were examined to assess their fatigue life under dynamic wind loads. First, wind tunnel tests using synchronous pressure models were conducted to obtain wind load time histories of these six buildings. Subsequently, time histories of wind-induced displacements and component stresses were calculated. The wind-induced fatigue life of each building was evaluated using the rain-flow counting method and the Palmgren–Miner rule, revealing that the fatigue life generally exceeds 400 years. The results demonstrate that tall steel structures designed according to current standards perform well in resisting wind-induced fatigue damage. Furthermore, when the ratio of the wind-induced root mean square (RMS) stress to the ultimate strength of a structural element reaches 0.125–0.164, the fatigue life of components may fall below the design life, indicating the necessity of considering potential fatigue damage. The RMS stress ratio can be preliminarily compared with the RMS stress ratio threshold proposed in this study to determine whether wind-induced fatigue damage needs to be considered in tall steel buildings. Finally, a simplified fatigue life prediction formula is established to provide approximate estimates for the fatigue life of tall steel buildings. Full article

The increasing use of wooden cladding in multi-storey buildings raises critical fire safety concerns, especially in ventilated façade systems where the chimney effect can accelerate vertical flame spread. This study combines theoretical analysis with three full-scale fire tests to investigate key factors influencing fire propagation, including the influence of façade design details. Results show that poorly constructed lintels and jambs significantly accelerate flame entry into ventilated cavities, while wooden fire barriers—despite being combustible—can delay flame spread if properly installed. These findings inform design recommendations and underscore the need for more robust fire safety strategies in modern timber construction. Full article

Dielectric covers are generally used to provide external protection to antenna systems by providing electromagnetic transparency. They are utilized in ground applications as well as for protecting airborne, Sat Com, terrestrial and underwater antenna installations. This paper presents a unique and universal design of dielectric sandwich-layered cover that can effectively protect antennas operating in a large frequency band from 1 GHz to 28 GHz, including millimeter-wave and microwave ranges, with minimum insertion loss for various incident angles. The proposed single dielectric cover may give sufficient protection for an entire tower or chimney housing multiple antennas, ranging from first-generation to fifth-generation microwave base-station antennas, as well as other wireless/broadcast antennas in millimeter or lower frequency ranges. In the first step, optimum dielectric constant and thickness of the dielectric cover are calculated numerically through a MATLAB (R2015a) code. In the second step, a floquet port analysis is performed to observe the insertion loss through the transmission coefficient against various frequency band-spectrums in microwave and millimeter-wave ranges for validation of the proposed synthesis. The ANSYS 18.2 HFSS tool is used for the purpose. In the third step, fabrication of the dielectric-layered structure is completed with the optimum design parameters. In the final step, the dielectric package is tested under various fabricated antennas in different frequency ranges. Full article

Biomass is a key energy resource in the current context of climate and energy crises, due to its lower carbon footprint compared to fossil fuels. However, wood-based energy presents several drawbacks: public health concerns related to pollutant emissions from combustion, and questions about the sustainability of the resource given the increasing demand for cleaner fuels. This study investigates the combustion of mixtures of wood pellets (WPs) and barley straw pellets (BSPs) in a domestic biomass boiler, with the aim of evaluating how such blends affect pollutant emissions and energy production under standard boiler operation, without modifications. Pellets were characterized using a bomb calorimeter and thermogravimetric analysis (TGA), while gaseous and particulate emissions were measured at the chimney using gas analyzers and an Engine Exhaust Particle Sizer (EEPS), respectively. The results show that high BSP proportions (>50%) are not compatible with domestic biomass boilers, as they led to a significant increase in gaseous pollutant emission. However, blends with moderate BSP shares (10 and 25%) can be successfully used, offering benefits in terms of reduced pollutant emissions and improved sustainability. Additionally, infrared and high-speed cameras were installed above the boiler furnace, equipped with an optical window, to provide new insights into the combustion process. Full article