Top Of Chimney Research Articles

Impact of the V CAP on induced turbulent air flow in a solar chimney: a computational study

In this paper, a 2D numerical simulation of a solar chimney with a top V cap was performed to evaluate the induced air flow degradation. Dimensions including the width of the cap and the cap offset from the top of chimney are specified as key parameters. Meanwhile, height and width of the chimney are fixed. The numerical model was confirmed to be accurate compared to the published data. The results showed that reducing the offset and increasing the width reduces airflow through the chimney. The effect of offset on chimney intake air is significant. When considering the addition of the top V cap, the airflow is reduced by about 20% compared to the chimney without a cap. This is because the cap forms three primary vortices including one vortex below the cap and two ones above the cap. The vortex under the cap in the direction from the absorber plate to the glass cover increases the air flow out of chimney at the side of the glass cover. The region with great turbulent kinetic energy forms at upper side of the cap. The air flow correlation as a function of the heat flux to the absorber plate, cap offset and cap width have been developed with errors of less than 2.5%.

Characterizing spatial burn severity patterns of 2016 Chimney Tops 2 fire using multi-temporal Landsat and NEON LiDAR data

The Chimney Tops 2 wildfire (CT2) in 2016 at Great Smoky Mountains National Park (GSMNP) was recorded as the largest fire in GSMNP history. Understanding spatial patterns of burn severity and its underlying controlling factors is essential for managing the forests affected and reducing future fire risks; however, this has not been well understood. Here, we formulated two research questions: 1) What were the most important factors characterizing the patterns of burn severity in the CT2 fire? 2) Were burn severity measures from passive and active optical remote sensing sensors providing consistent views of fire damage? To address these questions, we used multitemporal Landsat- and lidar-based burn severity measures, i.e., relativized differenced Normalized Burn Ratio (RdNBR) and relativized differenced Mean Tree Height (RdMTH). A random forest approach was used to identify key drivers in characterizing spatial variability of burn severity, and the partial dependence of each explanatory variable was further evaluated. We found that pre-fire vegetation structure and topography both play significant roles in characterizing heterogeneous mixed burn severity patterns in the CT2 fire. Mean tree height, elevation, and topographic position emerged as key factors in explaining burn severity variation. We observed generally consistent spatial patterns from Landsat- and lidar-based burn severity measures. However, vegetation type and structure-dependent relations between RdNBR and RdMTH caused locally inconsistent burn severity patterns, particularly in high RdNBR regions. Our study highlights the important roles of pre-fire vegetation structure and topography in understanding burn severity patterns and urges to integrate both spectral and structural changes to fully map and understand fire impacts on forest ecosystems.

Construction of New Branching Point and Operation of New Primary Beam Line at the J-PARC Hadron Facility

Construction of a new primary beam line, called the B-line, started in 2013 at the J-PARC Hadron Experimental Facility. The B-line is branched at the middle of an existing primary proton beam line (A-line) in the beam switching yard (SY), which is the connecting tunnel between the Main Ring (MR) and the Hadron experimental hall (HD-hall). At the branching point, about 0.1% of the primary beam is kicked off at 5 degrees using a Lanbertson magnet and two septum magnets. The Lambertson magnet has a field free hole in its yoke. The proton beam that goes through a field region is separated from the A-line, and it is extracted to the B-line. The rest of the beam that goes through the field free hole is transported through the existing primary beam line. Since a significant beam loss as much as 420 W occurs at the edge of field free hole, the magnets near the Lambertson magnet are operated under a very high radioactive environment. We have developed a “mini-chimney system” regarding easy maintenance of those magnets. The mini-chimney means a vertical tower of approximately 1m in height. The tower is comprised of water pipes, power electrodes, and signal cables for safety interlock. Those can be easily connected and disconnected at the top of chimney on the ceiling iron shields. In this paper we summarize the maintenance scheme developed for the B-line, as well as the design of B-line.In May 2020, the first proton beam was successfully extracted to the B-line by means of the Lambertson and the septum magnets. Up to now, the 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sup> protons per 5.2 sec accelerator cycle shot have been available.

Using an IIIF as trunk approach to digital collections delivery: Case study of the Rising from the Ashes Oral History Project

Rising from the Ashes: The Chimney Tops 2 Wildfires Oral History Project is a project led by the University of Tennessee Libraries in collaboration with the City of Gatlinburg and the Anna Porter Public Library. The community-based oral history project documents the immediate and ongoing impacts of the 2016 Chimney Tops 2 wildfires, one of the largest natural disasters in Tennessee history, by recording interviews with individuals who experienced the wildfires or their aftermath. The interviews were conducted in both English and Spanish and comprise a mix of both video and audio-only recordings. While transitioning to a new repository system, the team decided to develop a stand-alone solution leveraging the IIIF presentation version 3 application programming interface for serving the oral histories. This paper describes the project and the team’s experience implementing the project to this new specification.

Modeling evacuation decisions in the 2019 Kincade fire in California

Communities around the world are increasingly exposed to larger and more intense wildfires. A common method that officials use to protect community members from harm is evacuation. Data on how people behave during wildfires is critical when planning for evacuation and deciding when and how to evacuate entire communities during an event. Using a similar method to the 2016 Chimney Tops 2 Fire study, an online survey was conducted with households impacted by the 2019 Kincade fire in Sonoma County, California. The survey measured pre-event and event-based factors to 1) predict household perceptions and evacuation decisions and 2) compare results across fire events. Regression analysis identified the factors that influenced risk perception at the time of evacuation decision, i.e., pre-fire perceptions of safety, household makeup (of adults, pets, and livestock), income, education and threat assessment. Logistic regression analyses found that risk perception, length of residence, household makeup, income, education, evacuation order, fire cues, pre-fire perceptions of the safety, and homeownership influenced evacuation decisions. These results differ widely from the 2016 fire due to differences in fire conditions and experiences across populations. Results from this work bring the field closer to a generalized theory of human behavior during wildfire evacuation and improve community-wide evacuation planning and real-time decision-making.

Loading of stream wood following the 2016 Chimney Tops 2 Wildfire: Great Smoky Mountains National Park, Tennessee, USA

AbstractLarge wood drives physical and ecological processes in river systems, but the relative roles of continuous individual tree mortality versus episodes of mass mortality in wood recruitment are not well understood. Here, the 2016 Chimney Tops 2 wildfire, a rare severe wildfire in the eastern United States, was used as a case study for examining the role of mass tree mortality in wood loads of streams in Great Smoky Mountains National Park (GSMNP), Tennessee. Wood surveys were conducted on four reaches in two drainage systems affected by the fire to ascertain the total frequency and volume of burned and unburned wood pieces and jams. Relative to unburned wood, the Chimney Tops 2 fire resulted in a major influx of burned wood to the study reaches, with large percentages of individual pieces (average of 47% by frequency, 48% by volume) and jams (average of 72% by frequency, 93% by volume) exhibiting burn marks. Burned wood pieces had a larger diameter than unburned pieces (p = .065). Results suggest that rare mass‐mortality events like the Chimney Tops 2 wildfire could play a major role in wood dynamics of mountain streams in humid forested regions.

Calibrating the Wildfire Decision Model using hybrid choice modelling

Wildfire occurrences is creating serious challenges for fire and emergency response services and a diverse range of communities around the world due to the increment of the occurrence of these disasters. As such, understanding the physical and social dynamics characterizing wildfires events is paramount to reduce the risk of these natural disasters. As such, one of the main challenges is to understand how households perceive wildfires and respond to them as part of the evacuation process.In this work, the Wildfire Decision Model originally proposed in Lovreglio et al. [1] is calibrated using a hybrid choice model formulation. The Wildfire Decision Model is a newly developed behavioural choice model for large-scale wildfire evacuations based on the estimation of the risk perceived by households and the impact that this has on the decision-making process. This model is calibrated using a hybrid choice modelling solution and survey data collected after the 2016 Chimney Tops 2 wildfire in Tennessee, USA. The proposed model shows good agreement with the preliminary findings available in the wildfire evacuation literature; namely, the perceived risk is affected by both external factors (i.e., warnings and fire cues) and internal factors (i.e., education, previous wildfire evacuation experience and time of residency in a property).

Performance study and economic analysis of wind supercharged solar chimney power plant

By setting up the unpowered wind pressure wheel at the chimney top, this paper puts forward the model of “wind supercharged solar chimney power plant (WS-SCPP)". Based on the prototype Spanish solar chimney power plant (SCPP), the physical, mathematical models are built, the performance of WS-SCPP and SCPP are compared and the relationship between chimney height increment and supercharging effect is discussed. The results show that: with the help of unpowered wind pressure wheel, the performance of WS-SCPP improves greatly. At the same turbine rotational speed, the shaft power of WS-SCPP is always higher than that of SCPP. When the speed is 100 rpm, the shaft power of SCPP increases from 37.8kw to 57.03kw, with an increase of 50.9%. The net income and NPV of WS-SCPP are always higher than those of SCPP. The lowest electricity selling price is significantly lower than that of SCPP, with a decrease of 20.1%. When the chimney height of SCPP is increased by at least 80 m, the performance is comparable to WS-SCPP. Wind supercharging technology is one of the effective ways to improve the efficiency and commercial application of SCPP.

Short-Term Effects of Recent Fire on the Production and Translocation of Pyrogenic Carbon in Great Smoky Mountains National Park

Fire affects the quantity and quality of soil organic matter (SOM). While combustion of the O-horizon causes direct losses of SOM, fire also transforms the remaining SOM into a spectrum of thermally altered organic matter. Pyrogenic carbon (PyC) can resist degradation and may have important effects on soil carbon cycling. The objectives of this study are to examine the mobility of PyC. Studying the effects of wildfire is challenging due to the rapid post-fire changes in the ecosystem and lack of robust controls. We overcame those limitations by examining the Chimney Tops 2 Fire which burned 4,617 ha of the Great Smoky Mountains National Park (GRSMNP), including a National Ecological Observatory Network (NEON) site, in November 2016. We examined PyC in soils from three time points from an area burned at low-severity (pre-, immediate post-, and 11 months post-fire) and two time points from areas burned at lower to higher severity (immediate post- and 11 months post-fire). At locations with pre-fire soil samples we found that PyC increased in the O-horizon (2.22 g BPCA/kg soil) after low severity fire, which resulted in higher PyC concentrations at 5-10 cm (0.73 g BPCA/kg soil and 17.79 g BPCA/kg C) and 10-20 cm (12.19 g BPCA/kg C) of depth in the mineral soil. Sites burned at higher severity had more PyC in the O horizon relative to sites burned at lower severity (10.29 g BPCA/kg soil and 29.89 g BPCA/kg C). As a result of higher concentrations of PyC in the O-horizons burned at higher severity, statistically more PyC moved from the O-horizon to the 0-10 cm horizon from immediate to 1-year post-fire (1.37 g BPCA/kg soil and 16.10 g BPCA/kg C). Lastly, the depth profile of C and BPCA suggest a shift in the source and amount of PyC in these soil profiles over time – possibly as a result of fire suppression. Results indicate that low severity fire may be an important mechanism by which PyC is produced and transported into mineral soils.

Public Management in an Era of the Unprecedented: Dominant Institutional Logics as a Barrier to Organizational Sensemaking

AbstractIn an era when unprecedented events are occurring with increasing frequency, public management theory is challenged to consider whether it is possible to better prepare agencies to respond to situations previously neither expected, nor even seriously imagined. In this paper, we consider the case of the 2016 Chimney Tops 2 wildfire that contributed to the destruction of neighborhoods in and around Gatlinburg, TN. We argue this case illuminates a critical gap in extant organizational theory concerning the factors that impede sensemaking processes, which are fundamental to models of high reliability organizations during unprecedented events. Specifically, based on insights from this case considered through an institutional lens, we theorize that the nature of unprecedented events undermines an adaptive response through both structural and cultural/institutional processes. Structurally, we demonstrate how public agencies evolve to the contingencies of their normal task environment, which we should anticipate will be maladapted to the task demands of an unprecedented event. However, we theorize the greater challenge lies in the processes by which these structural features of the agency, over time, create, and reinforce a dominant institutional logic which can delay and weaken sensemaking processes, even when discrepant environmental cues are present. We conclude with a discussion of remedies that may facilitate earlier recognition, and thus more effective agency response, when the unprecedented is occurring.

Modelling evacuation decision-making in the 2016 Chimney Tops 2 fire in Gatlinburg, TN

As wildfires occurring at the wildland–urban interface (WUI) continue to become more severe, there is an increasing need to understand human behaviour in these situations, and evacuation decision-making in particular. To contribute to this understanding, an online survey (using both mail and online sampling methods) was disseminated to households impacted by the 2016 Chimney Tops 2 fire in Tennessee. The survey instrument measured pre-event variables such as awareness of fire risks and previous experience with evacuations as well as the types of warnings and fire cues received during the event, with a focus on factors known to impact evacuation decisions and risk perception. Using linear and logistic regression analyses, it was found that fire cues and receiving warnings from a trusted source influenced risk perceptions leading up to an evacuation decision. In line with the Protective Action Decision Model, risk perception also highly influenced evacuation decisions, along with other variables, i.e. gender and prior preparation actions. Results from this work provide support for findings from previous wildfire evacuation research as well as produce some novel findings, along with several methodological recommendations, which will be further explored.

Context dependent fungal and bacterial soil community shifts in response to recent wildfires in the Southern Appalachian Mountains

Decades of fire suppression coupled with changing climatic conditions have increased the frequency and intensity of wildfires. The Southern Appalachia region of the United States is predicted to be particularly susceptible to climatic changes, with predicted increases in fire severity and occurrence. Following the record breaking fire season in 2016 in Southern Appalachia, we examined wildfire impacts on soil chemistry and below ground communities (fungi and bacteria – Illumina MiSeq) within two substrates (duff and soil) at two adjacent locations with similar plant communities (Great Smoky Mountains National Park – ‘Chimney Top 2’ Fire (GRSM) and Nantahala National Forest – ‘Cliffside’ Fire (NNF)) from replicate plots representing a range of fire severities (unburned, low severity, moderate severity, severe). Differing fire severities changed community composition, and fire severity played a stronger role in structuring bacterial communities than in structuring fungal communities. Further, fire impacts on soil communities and functional guilds responses were location- and substrate-specific with NNF responding more strongly to fire than GRSM. Additionally, using a novel analysis tool (Axis Weighted Ordination Distance – AWOrD), domain and location specific responses to wildfire severity are demonstrated. Taken together, our results suggest context-dependency in microbial responses to fire that must be accounted for to generate ecosystem-wide recovery predictions.

A High Resolution Coupled Fire–Atmosphere Forecasting System to Minimize the Impacts of Wildland Fires: Applications to the Chimney Tops II Wildland Event

Wildland fires are responsible for large socio-economic impacts. Fires affect the environment, damage structures, threaten lives, cause health issues, and involve large suppression costs. These impacts can be mitigated via accurate fire spread forecast to inform the incident management team. We show that a fire forecast system based on a numerical weather prediction (NWP) model coupled with a wildland fire behavior model can provide this forecast. This was illustrated with the Chimney Tops II wildland fire responsible for large socio-economic impacts. The system was run at high horizontal resolution (111 m) over the region affected by the fire to provide a fine representation of the terrain and fuel heterogeneities and explicitly resolve atmospheric turbulence. Our findings suggest that one can use the high spatial resolution winds, fire spread and smoke forecast to minimize the adverse impacts of wildland fires.

Study of solar chimney in Tunisia: Effect of the chimney configurations on the local flow characteristics

The electric power production using solar chimney power plant is directly related to the velocity value along the chimney. In this work, the effect of the chimney configuration on the solar chimney power plant performance was investigated. A series of numerical simulations were conducted to simulate the turbulent flow. An experimental setup was developed in Tunisia to carry out several measurements. The comparison between the numerical and the experimental results showed a good agreement. The study focused on studying the solar chimney power plants with: standard, divergent, convergent and opposing chimney. The velocity fields, the static pressure, the magnitude velocity and the temperature distribution were presented and discussed. The results revealed that the chimney form affects the air velocity behavior. The maximum velocity emerges with divergent configuration. However, the others configurations adjust the maximum velocity location, in the chimney center for the opposing configuration, and in the chimney top for the convergent configuration. This variation is due to the static pressure distribution affected the chimney configuration change.

Use of electrostatic precipitators in small-scale biomass furnaces to reduce particulate emissions from a range of feedstocks

The results of a study into the precipitation efficiencies of two different electrostatic precipitator (ESP) types (chimney top with manual cleaning and in-line with automated cleaning) using three biomass fuels with low (wood), medium (willow) and high (tall fescue) particulate emission levels are presented. Testing showed that precipitation efficiencies of greater than 70% are possible in an inline system with automated cleaning, while in the chimney top, manual cleaning system high efficiencies can be achieved for willow (86%) and wood (69%) on a short term basis. For low emission fuels such as wood ( 100 mg Nm−3) and high (tall fescue > 300 mg Nm−3) emission fuels it was found that the use of an automated cleaning system is necessary to maintain precipitation efficiencies at acceptable levels. In the chimney top type, system efficiencies dropped to zero with willow after 50 h and with tall fescue after 10 h of combustion with no cleaning, due to build-up of particulate matter on the electrode causing reduced distribution of charge to the oncoming particles. For the in-line system, it was also shown that an improved electrode design had the capacity to increase precipitation efficiency by on average 18%. It was concluded that ESPs have an important role to play in particulate emission reduction in future low emission biomass combustion systems if they are to meet stricter particulate control guidelines.

A numerical study of flow and mixing characteristics inside the chimney structure of a pool type research reactor

Numerical studies were performed to examine the effects of flow velocities of opposing streams on the flow pattern and turbulent mixing characteristics in a three-dimensional chimney structure using CFD code PHOENICS. This chimney structure facilitates guiding of the radioactive water from the reactor core (i.e., core flow) towards the side outlet nozzles and simultaneously drawing out water from the reactor pool through the chimney top. The radioactive water flows upward and has a tendency to reach to the pool top through the chimney top which is open for fuel and isotope handling. The chimney design allows drawing out a part of the pool water in the downward direction to suppress the upward flowing radioactive water jet. This downward flow through the chimney is compensated by providing additional core bypass flow to the pool. Analyses were carried out on 1:1 chimney structure and also on 1/6th scaled down chimney model to understand the similarity of behaviour of the model and the prototype. Mass flow rate of upward flowing water (i.e. core flow) is considered to be 750kg/s and core bypass flow is varied from 0% to 15% that of the core flow. In the model study, mass flow rate was varied from 8.33 to 25kg/s and core bypass flow was considered to vary from 0% to 15%. Flow mixing pattern inside the chimney and the non-dimensional stagnation depth was predicted for the model and the prototype. It was observed that there is a good similarity in behaviour of the prototype and model.

Potential release of hydrogen fluoride from domestic coal in endemic fluorosis area in Guizhou, China

Almost half of the total rural area of Guizhou Province and many regions within the 11 adjacent provinces in southwestern China have a long history (at least 70 years) of endemic fluorosis, including dental fluorosis and osteofluorosis along with its associated deformities and disabilities. Over decades of research, this specific type of endemic fluorosis has been defined as coal-burning fluorosis, which is distinct from drinking-water fluorosis. It is generally acknowledged that indoor burning and combustion of high-fluorine coal leads to food contamination, and fluorine then enters the human body. However, the exact chemical form of fluorine during its release and transfer to the body is still unknown. In the present study, 21 domestic coal samples from outcrop and semi-outcrop coal collected in five villages with fluorosis were analyzed by time-of-flight secondary ion mass spectrometry (TOF-SIMS). The total mass fraction of sulfur in the samples ranged from 0.24%–5.58% and total fluorine content ranged 90.2–149.2 mg/kg. H3O+, H2SO 4 + and HSO 4 − were detected in the samples by TOF-SIMS, which indicated that sulfuric acid hydrate (H2SO4·H2O) was present in the samples. F− was detected in all of these, which suggested the samples contain ionic fluorine compounds. Under certain circumstances, such as heating or burning, the prevalence and coexistence of the acid (H2SO4·H2O) and base (F−) would lead to a neutralization reaction producing volatile hydrogen fluoride (HF, bp = 19.5°C). This would be the chemical form of fluorine released from the coal. Further studies using HF and SO2 test tubes on headspace gas over coal samples heated to 200°C in the laboratory and on headspace gas over stoves or chimney tops at rural residences confirmed the release of HF.

Numerical Modeling of Gas Hydrate Accumulation in the Marine Sediments of Shenhu Area, Northern South China Sea

AbstractShenhu is located in the middle of northern South China Sea. The bottom simulating reflector (BSR) exists widely in the area, and the strong BSR appears mostly in the diapiric structure or at the top of gas chimney. Drilling showed that gas hydrate was only distributed in the upper 10~25 m range above the bottom of hydrate stability zone (BHSZ), but with the maximum saturation of up to 48%. We designed a 2D numerical model to simulate the formation and accumulation in the marine sediments, aiming to understand this unique feature of gas hydrate, as well as to study the relationship between gas chimneys, mud diapirism and gas hydrate reservoir. Modeling results indicate that, the methane from deep moves upward vertically and is confined to a rather narrow range, which is shown as gas chimney in the seismic section and BSR at its top. During the process of slow movement of gas, the BSR (top of gas chimney) is always lower than the BHSZ controlled by temperature and pressure. Unless it crosses the BHSZ hydrate cannot form. In case the hydrate forms, the stratum becomes a sealing layer, thereby preventing the continued migration of methane. Consequently, the hydrate only forms within a very thin layer above the BHSZ, but the saturation can be very high. After that, if the gas supply from deep stops, the gas chimney will gradually disappear, leaving only the hydrate. So, the existence of gas chimney does not necessarily correspond to hydrate. In addition, the modeling results also show that the fracture fluid activity (diapir) is not always favorable to the hydrate formation. If the fluid flow from deep is very large, all the methane may dissolve in fluid once produced, and is taken away. Thus, no free gas and hydrate is able to form. Only when the methane flow matches the fluid flow can the hydrate form. Therefore, the larger the fluid flow, the more difficult to form hydrate.

DESIGN OF VIBRATION-DAMPERS FOR STEEL CHIMNEYS WITH LATEST FEATURES

In the past there have been attempts to control wind response of chimneys using strakes, perforated screens, rubber mountings, hanging chain dampers and tuned mass dampers. However, a systematic and detailed study on latest designed vibrationdampers at chimney top is not seen in literature. In the present paper, principle of the damping system is discussed. Mass and stiffness of the damper are calculated. Amplitude of the top of chimney during vortex shedding is calculated. Results thus obtained have been discussed. Some latest damping systems have also been presented for authenticity.

하나로 수조 방사선 준위의 저감 특성

HANARO, 30㎿ of research reactor, was installed at the depth of 13m in an open pool. The 90% of primary coolant was designed to pass through the core and to remove the reaction heat of the core. The rest, 10%, of the primary coolant was designed to bypass the core. And the reactor coolant through and bypass the core was inhaled at the top of chimney by the coolant pump to prevent the radiated gas from being lifted to the top of reactor pool. But, the part of core bypass coolant was not inhaled by the reactor coolant pump and reached at the top of reactor pool by natural convection, and increased the radiation level on the top of reactor pool. To reduce the radiation level by protecting the natural convection of the core bypass flow, the hot water layer (HWL, hereinafter) was installed with the depth of 1.2m from the top of reactor pool. As the HWL was normally operated, the radiation level was reduced to five percent (5%) in comparing with that before the installation of the HWL. When HANARO was operated at a higher temperature than the normal temperature of the HWL by operating the standby heater, it was found that the radiation level was more reduced than that before operation. To verify the reason, the heat loss of the HWL was calculated by Visual Basic Program. It was confirmed through the results that the larger the temperature difference between the HWL and reactor hall was, the more the evaporation loss increased. And it was verified that the radiation level above was reduced more safely by increasing the capacity of heater.