Analytical Modeling of Fire Smoke Spread in High-rise Buildings

Canada has a large number of high-rise buildings; according to the National Fire Protection Association (NFPA) 101 Life Safety Code, a high-rise building is defined as a building with the height of more than 23 meters or that is roughly 7 stories tall. Fires in high-rise buildings are often disastrous and cause huge losses if the buildings are not well protected against fires. Historically, a high-rise fire is more likely to happen in the lower floors according to the statistics. Driven by stack effect, the resulting smoke from fires may spread to the higher levels more easily via the vertical shafts, e.g. stairs, elevators, light wells, ventilation ducts, than through leakage openings in the building structure. It was reported that smoke spread through shafts counts for about 95% or more of the upward movement of smoke in typical high-rise buildings. Therefore, much attention has been paid to the study of the smoke movement in vertical shafts. Analytical models, numerical simulations and experimental studies are the commonly used methods to study the smoke movement through building shafts. For simplification, most of the previous studies on the analytical models and numerical simulations assumed adiabatic shaft walls and did not take heat transfer between smoke and shaft boundaries into consideration. In fact, the smoke temperature strongly depends on the heat exchange with the shaft walls and may vary significantly depending on the height. An accurate estimation of the temperature profile in a shaft is crucial for the prediction of smoke movement during a fire, because the amount of smoke spreading through a shaft is closely coupled with the heat transfer during a fire. Numerical approaches normally include CFD model, zone model and mutizone network model, in which the mutizone network model is often used to study smoke movement during fires in high-rise buildings but temperature in each zone has to be specified by users due to the lack of energy model, which may results in errors in stimulation. In addition, full size experiments are often costly and unpractical to conduct, especially for high-rise buildings. Sub-scale experiment is the often used one but it lacks sound scaling law to maintain the similarity of scaled and full-size high-rise models. The main objective of this research is to develop an analytical model and a numerical modeling approach of coupled heat and mass transfer of fire smoke movement through vertical shafts of high-rise buildings. Based on the analytical model, simple calculation method and empirical equation of neutral plane level were developed and validated by experimental data from the literature. It was found that the empirical equation is more accurate than the existing equation of neutral plane level. Studies on the dimensionless analytical solutions and similarity study were also conducted using the analytical model, which provide a new scaling method to sub-scale smoke spreads in high-rise shafts. The new scaling method was verified by experiments on different size and material shafts. The results indicated that compared to the common used scaling method, Froude modeling method, the new scaling method could achieve closer results between sub-scaled models and the full-size model. The numerical approach is based on a multizone program with an added energy equation, CONTAM97R, which can calculate the coupled heat and mass transfer inside the high-rise shafts. Different from floor zoning strategy (FZS) that is frequently used, a new zoning strategy called adaptive zoning strategy (AZS) was suggested by adapting the temperature gradient inside the shaft. Using this zoning strategy, a modeling method of smoke movement in shafts during high-rise fires by the mutilizone and energy network program was proposed. It was concluded that AZS could achieve similar accuracy results as FZS but with fewer zones

Study of fire smoke movement from building integrated photovoltaic (BIPV) double skin façade (DSF) fires using helium gas

Abstract: Advanced building technologies such as building integrated photovoltaics (BIPVs) systems have been widely applied in new and existing constructions, in order to reduce energy consumption and electricity demand in buildings. Meanwhile they can cause a new critical challenge, i.e., fire safety issues. On the one hand, plume from the PV panel fires could spread into the buildings through the windows and ventilation openings. On the other hand, the risk of fire can be elevated by affecting the propagation of fire inside and outside the building. Furthermore, interfering with the smoke and venting system, firefighting operation, and electrical shock dangers. Most of the studies on the PV panels are to find the cause of failure, improving the cell efficiency, cost reduction and extracting maximum power, while there is the need to study the mechanism for smoke propagation as well. Applying BIPV on the building cause major changes in the traditional method of using structural components. These changes may include changes in the material, standard distances, gaps, and duties of elements, each of which can bring new fire safety issues.Résumé de la communication présentée lors du congrès international tenu conjointement par Canadian Society for Mechanical Engineering (CSME) et Computational Fluid Dynamics Society of Canada (CFD Canada), à l’Université de Sherbrooke (Québec), du 28 au 31 mai 2023

Evaluating Wind-driven Natural Ventilation Potential for Early Building Design

Natural ventilation is widely applied in buildings considering its potential of improving indoor air quality and saving building energy costs. However, to evaluate its viability and determine the ventilation rates quickly and relatively accurately during early design stage is challenging. This paper explores a fast and accurate evaluation approach in the form of empirical equations to estimate the ventilation rate and potential of wind-driven natural ventilation. By using computational fluid dynamics (CFD) with results validated for both cross and single natural ventilation strategies, this study conducted a series of simulations to determine critical ventilation coefficients for the empirical equations as functions of wind direction, speed and building height. The proposed evaluation approach could help architects and engineers to evaluate the viability of natural ventilation during early building design. This approach was also demonstrated to evaluate the potential of natural ventilation in 65 cities of North America so a series of natural ventilation potential maps were generated for a better understanding of natural ventilation potential in different climates and for the climate-conscious design of buildings in North America

Systematic identification of genes involved in divergent skeletal muscle growth rates of broiler and layer chickens

<p>Abstract</p> <p>Background</p> <p>The genetic closeness and divergent muscle growth rates of broilers and layers make them great models for myogenesis study. In order to discover the molecular mechanisms determining the divergent muscle growth rates and muscle mass control in different chicken lines, we systematically identified differentially expressed genes between broiler and layer skeletal muscle cells during different developmental stages by microarray hybridization experiment.</p> <p>Results</p> <p>Taken together, 543 differentially expressed genes were identified between broilers and layers across different developmental stages. We found that differential regulation of slow-type muscle gene expression, satellite cell proliferation and differentiation, protein degradation rate and genes in some metabolic pathways could give great contributions to the divergent muscle growth rates of the two chicken lines. Interestingly, the expression profiles of a few differentially expressed genes were positively or negatively correlated with the growth rates of broilers and layers, indicating that those genes may function in regulating muscle growth during development.</p> <p>Conclusion</p> <p>The multiple muscle cell growth regulatory processes identified by our study implied that complicated molecular networks involved in the regulation of chicken muscle growth. These findings will not only offer genetic information for identifying candidate genes for chicken breeding, but also provide new clues for deciphering mechanisms underlining muscle development in vertebrates.</p

PO-037 Validation Of Capillary Blood Gas Analysis For The Assessment Of Training Load In Track Cycling

Objective The energy supply of daily training of track cycling should be mainly by anaerobic metabolism, which can make the blood buffer capacity facing huge Challenge and being improved. The arterialized capillary blood gas analysis can be a reliable method to evaluate the blood status of base-acid balance, which may reflect the effect of exercise intensity on blood buffer system. The paper&nbsp;validate the blood gas analysis as a reliable method for evaluating the total periodical training load of track cyclists. Methods Five male and five female elite track cyclists performed two phases (four weeks per phase) of training respectively. The content included the track specific, strength and aerobic training. The Borg's Rating of Perceived Exertion (RPE) Scale (0-11) was recorded in the ten minutes after each session and calculated the session RPE (sRPE). The total inertial load (TIL) was calculated by sRPE sum from Monday to Thursday. The arterialized capillary blood gas analysis was performed at 7:00 AM on Monday and Friday. The delta value (ΔPH, ΔPCO2, ΔTCO2, ΔHCO3-, ΔBE, ΔPO2, ΔSO2) were calculated by Friday minus Monday. Pearson's linear correlation was applied to calculate the correlation between TIL and delta value. Independent t test was used to test the differences between two genders. Results There was the moderate correlation between TIL with ΔPH and ΔHCO3- (Correlation Coefficient= 0.712 and 0.642 respectively,&nbsp;P&lt;0.01). But other blood gas indexes didn’t show the obvious relationship with TIL (Correlation Coefficient &lt;&nbsp;0.5). There was no differences for TIL between male and female (3870.1±788.4 vs. 4130.2±716.7,&nbsp;P&gt;.05). Moreover, ΔHCO3- of male was significant more than female by 95.1% (P&lt;0.01). There were significant correlation between TIL and ΔPH for both male and female (Correlation Coefficient= 0.785 and 0.812 respectively,&nbsp;P&lt;0.01), and between TIL and ΔPH for both male and female (Correlation Coefficient= 0.662  and 0.658 respectively,&nbsp;P&lt;0.01). Conclusions The PH value and bicarbonate radical of blood should be sensitive to the high intensity track cycling training, which can be the valid to evaluate the inertial load. However, gender has no influence on evaluating. The oxygen partial pressure and oxygen saturation of blood can not reflect the training load accurately

Parametric study of air curtain door aerodynamics performance based on experiments and numerical simulations

Air curtains have been widely used to reduce infiltration through door openings and save heating/cooling energy in different types of buildings. Previous studies have found that there exist three aerodynamics conditions: optimum condition (OC), inflow break-through (IB), and outflow break-through (OB) conditions, which are important for categorizing air curtain performance subject to such key parameters including supply speed and angle, and presence of a person during an actual operation. However, few studies have focused on the effects of these parameters on air curtain performance in terms of resisting infiltration and reducing exfiltration. This research presents a parametric study of air curtain performance based on reduced-scale experiments and full-scale numerical simulations. It was found that increasing air curtain supply angle improves air curtain performance when it is operated under the OC and IB conditions but creates excessive exfiltration under the OB condition. Increasing supply speed of air curtain generally improves the air curtain performance whereas this improvement deteriorates with the increase of supply angle under the OB condition. The presence of person, either directly under or below the air curtain, almost has no effect on the infiltration/exfiltration during the OC condition. Moreover, the person in the doorway can block airflow from both directions, contributing to less infiltration under the IB condition and less exfiltration under the OB condition than without the person. This study provides valuable insights into air curtain aerodynamics performance under different operational conditions and key contributing parameters

Time to Benefit of Sodium-Glucose Cotransporter-2 Inhibitors Among Patients With Heart Failure

IMPORTANCE Emerging evidence has consistently demonstrated that sodium-glucose cotransporter 2 (SGLT2) inhibitors reduce the risk of heart failure (HF) hospitalization and cardiovascular (CV) death among patients with HF. However, it remains unclear how long a patient needs to live to potentially benefit from SGLT2 inhibitors in this population. OBJECTIVES To estimate the time to benefit from SGLT2 inhibitors among patients with HF. DESIGN, SETTING, AND PARTICIPANTS This comparative effectiveness study systematically searched PubMed for completed randomized clinical trials about SGLT2 inhibitors and patients with HF published until September 5, 2022; 5 trials with the year of publication ranging from 2019 to 2022 were eventually included. Statistical analysis was performed from April to October 2022. INTERVENTION Addition of SGLT2 inhibitors or placebo to guideline-recommended therapy. MAIN OUTCOMES AND MEASURES The primary outcome was the time to first event of CV death or worsening HF, which was broadly comparable across the included trials. RESULTS Five trials consisting of 21 947 patients with HF (7837 [35.7%] were female; mean or median age older than 65 years within each trial) were included. SGLT2 inhibitors significantly reduced the risk of worsening HF or CV death (hazard ratio [HR], 0.77 [95% CI, 0.73-0.82]). Time to first nominal statistical significance (P < .05) was 26 days (0.86 months), and statistical significance was sustained from day 118 (3.93 months) onwards. A mean of 0.19 (95% CI, 0.12-0.35) months were needed to prevent 1 worsening HF or CV death per 500 patients with SGLT2 inhibitors (absolute risk reduction [ARR], 0.002). Likewise, 0.66 (95% CI, 0.43-1.13) months was estimated to avoid 1 event per 200 patients with SGLT2 inhibitors (ARR, 0.005), 1.74 (95% CI, 1.07-2.61) months to avoid 1 event per 100 patients (ARR, 0.010), and 4.96 (95% CI, 3.18-7.26) months to avoid 1 event per 50 patients (ARR, 0.020). Further analyses indicated a shorter time to benefit for HF hospitalization and among patients with diabetes or HF with reduced ejection fraction. CONCLUSIONS AND RELEVANCE In this comparative effectiveness research study of estimating the time to benefit from SGLT2 inhibitors among patients with HF, a rapid clinical benefit in reducing CV death or worsening HF was found, suggesting that their use may be beneficial for most individuals with HF

Resilient cooling strategies – A critical review and qualitative assessment

The global effects of climate change will increase the frequency and intensity of extreme events such as heatwaves and power outages, which have consequences for buildings and their cooling systems. Buildings and their cooling systems should be designed and operated to be resilient under such events to protect occupants from potentially dangerous indoor thermal conditions. This study performed a critical review on the state-of-the-art of cooling strategies, with special attention to their performance under heatwaves and power outages. We proposed a definition of resilient cooling and described four criteria for resilience—absorptive capacity, adaptive capacity, restorative capacity, and recovery speed —and used them to qualitatively evaluate the resilience of each strategy. The literature review and qualitative analyses show that to attain resilient cooling, the four resilience criteria should be considered in the design phase of a building or during the planning of retrofits. The building and relevant cooling system characteristics should be considered simultaneously to withstand extreme events. A combination of strategies with different resilience capacities, such as a passive envelope strategy coupled with a low-energy space-cooling solution, may be needed to obtain resilient cooling. Finally, a further direction for a quantitative assessment approach has been pointed out

AI is a viable alternative to high throughput screening: a 318-target study

: High throughput screening (HTS) is routinely used to identify bioactive small molecules. This requires physical compounds, which limits coverage of accessible chemical space. Computational approaches combined with vast on-demand chemical libraries can access far greater chemical space, provided that the predictive accuracy is sufficient to identify useful molecules. Through the largest and most diverse virtual HTS campaign reported to date, comprising 318 individual projects, we demonstrate that our AtomNet® convolutional neural network successfully finds novel hits across every major therapeutic area and protein class. We address historical limitations of computational screening by demonstrating success for target proteins without known binders, high-quality X-ray crystal structures, or manual cherry-picking of compounds. We show that the molecules selected by the AtomNet® model are novel drug-like scaffolds rather than minor modifications to known bioactive compounds. Our empirical results suggest that computational methods can substantially replace HTS as the first step of small-molecule drug discovery

Investigation of photovoltaic roof fire-induced smoke spread under wind effect

Abstract: Photovoltaic (PV) panels have been installed seven times more over the last decade. However, the number of fires caused by PV panels has also increased. Based on the forecast, PV power generation capacity is expected to exceed 1 TW in 2022, and 30% of PV installations are rooftops. A statistical prediction indicates that 27,166 fires will occur in 2021 and 28,900 fires will occur in 2022, with 8,670 of those fires occurring on solar roofs. In buildings, however, there are very few studies on the spread of PV fireinduced smoke, especially when it is accompanied by wind, which is essential for life safety. This study fills this research gap by proposing a new similarity law and a method for substituting pure helium gas for real fire smoke in order to study PV roof fireinduced smoke movement in the non-fireproof wind tunnel. As a result, the heat release rate (HRR) of PV fires, wind speed, and roof angle of the wind tunnel are tested. It is possible to substitute the HRR and smoke temperature for a certain volumetric flow rate and helium concentration. As a next step, the critical values are determined by a parametric study of HRR, wind speed, and roof angle. Based on the findings, three conclusions can be drawn: 1) a greater HRR results in greater smoke infiltration, 2) a lower wind speed causes stronger separation flow to blow smoke into the building via the leeward skylight, 3) flat roofs and 15°roofs are the most dangerous because of smoke infiltration, conversely, 60°roofs are the safest.Résumé de la communication présentée lors du congrès international tenu conjointement par Canadian Society for Mechanical Engineering (CSME) et Computational Fluid Dynamics Society of Canada (CFD Canada), à l’Université de Sherbrooke (Québec), du 28 au 31 mai 2023