scholarly journals Spread of smoke and heat along narrow air cavity in double-skin façade fires

2014 ◽  
Vol 18 (suppl.2) ◽  
pp. 405-416 ◽  
Author(s):  
Lun Chow
Keyword(s):  
Air Temperature ◽  
Vertical Channel ◽  
Cavity Depth ◽  
Glass Pane ◽  
Air Cavity ◽  
One Dimensional ◽  
Hot Gas ◽  
Heat Transfer Theory ◽  
Smoke Spread ◽  
Double Skin

A scenario on double-skin fa?ade fire was identified earlier for hazard assessment. A flashover room fire occurred next to the fa?ade, broke the interior glass pane and spread to the fa?ade cavity. As observed in experiments, hot gas moved up as a vertical channel flow for narrow fa?ade cavity. Heat and smoke spread along the narrow air cavity of a double-skin fa?ade will be studied in this paper. A simple mathematical model is developed from basic heat transfer theory for studying the vertical air temperature profiles of the hot gas flowing along the cavity. Assuming one-dimensional flow for hot gas moving up the fa?ade cavity, conservation equations on mass and enthalpy were solved. Experimental results on two double-skin fa?ade rigs of height 6 m and 15 m with narrow cavity depth were used to justify the results. A total of 11 tests were carried out. Correlation expressions between cavity air temperature and the height above ceiling of the fire room were derived.

scholarly journals NUMERICAL STUDIES ON SMOKE SPREAD IN THE CAVITY OF A DOUBLE-SKIN FAÇADE / SKAITINIS DŪMŲ SKLIDIMO DVIGUBO FASADO ERTMĖJE TYRIMAS

2011 ◽  
Vol 17 (3) ◽  
pp. 371-392 ◽  
Author(s):  
Cheuk Lun Chow
Keyword(s):  
Fire Hazard ◽  
Vertical Channel ◽  
Fire Dynamics ◽  
Cavity Depth ◽  
Air Cavity ◽  
Numerical Studies ◽  
Architectural Feature ◽  
Smoke Spread ◽  
Double Skin ◽  
Level Model

Double-skin façade (DSF) is an environmental friendly architectural feature. However, fire hazard is a concern. A scenario of having a flashover room fire adjacent to the façade was identified. Heat and mass would be trapped in the façade cavity. This paper examines air flow driven out of a flashover room fire to the cavity of a DSF by Computational Fluid Dynamics. The software Fire Dynamics Simulator developed at the Building and Fire Research laboratory, National Institute of Standards and Technology, USA was selected as the simulation tool. Three DSF features labeled as DSF1, DSF2 and DSF3 were considered. Detailed simulations were carried out to understand the fire-induced aerodynamics in a 5-level model DSF1 with a fire room at the third level. Hot gas spreading out to the façade cavity was simulated under two heat release rates of 1 MW and 5 MW. Air cavity depths of 0.5 m, 1 m, 1.5 m and 2 m were considered. Three stages of flame spreading out to a DSF with a wide air cavity depth were identified. Results suggested that wider air cavity depths would be more dangerous, with higher risk of the upper interior glass pane's breaking. To study spreading of heat and mass up the façade cavity as vertical channel flow, two taller DSF façade features DSF2 and DSF3 with differing air cavity depths were simulated. Both features were of height 24 m but of differing fire room height. Vertical temperature profiles with and without the DSF feature were compared. Santrauka Dvigubas fasadas yra ekologiškas architektūrinis sprendimas. Tačiau dvigubas fasadas yra problemiškas gaisrinės saugos požiūriu. Nagrinėjamas scenarijus, kai greta dvigubo fasado esančioje patalpoje įvyksta gaisro pliūpsnis. Dvigubo fasado ertmėje gali būti uždaryti karštis ir masė. Taikomi skaitmeninės skysčių dinamikos metodai nustatyti, kaip iš patalpos, kurįoje įvyksta gaisro pliūpsnis, oras ir degimo produktai išstumiami ī dvigubo fasado ertmę. Modeliuoti naudojama kompiuterinė programa, parengta JAV Nacionaliniame standartų ir technologijos institute. Nagrinėjami trys dvigubų fasadų sprendimai. Atliekamas detalus pirmojo sprendimo fasado modeliavimas siekiant suprasti gaisro lemiamą aerodinamiką penkių aukštų fasade, kai gaisras kyla trečiame aukšte. Modeliuojamas karštu dujų sklidimas iš fasado ertmės viršaus teigiant, kad gaisro išskiriama Siluma yra 1 MW ir 5 MW. Ertmės plotis imamas lygiu 0,5 m, 1,5 m ir 2 m. Nustatomi trys liepsnos sklidimo iš dvigubo fasado etapai. Gauti rezultatai leidžia daryti išvadą, kad platesni fasadai yra pavojingesni, nes didina viršutinių stiklo diskų dužimo tikimybę. Aukštesni antro ir trečio sprendimo fasadai naudoti tirti, kaip karštis ir masė juda vertikalia fasado ertme. Skyrėsi šių fasadų ertmės plotis. Abu fasadai buvo 24 m aukščio, tačiau skyrėsi gaisro patalpos aukštis. Buvo palygintas vertikalusis temperatūros pasiskirstymas dvigubo fasado ertmėje.

scholarly journals Detection of isoprene traces in exhaled breath by using photonic crystals as a biomarker for chronic liver fibrosis disease

2021 ◽  
Author(s):  
Ahmed Mehaney ◽  
Hussein A. Elsayed ◽  
Ashour M. Ahmed
Keyword(s):  
Liver Fibrosis ◽  
Photonic Crystals ◽  
High Sensitivity ◽  
Dielectric Materials ◽  
Exhaled Breath ◽  
Air Cavity ◽  
One Dimensional ◽  
Sensor Structure ◽  
Volatile Organic ◽  
First Time

Abstract Detection of blood-carried volatile organic compounds (VOCs) existing in the exhaled breath of human is an attractive research point for noninvasive diagnosis of diseases. In this research, we introduce a novel application of photonic crystals (PCs) for the detection of isoprene traces in the exhaled breath as a biomarker for liver fibrosis. This idea is introduced for the first time according to the best of our knowledge. The proposed sensor structure is a one-dimensional (1D) PC constructed from a multilayer stack of two dielectric materials covered with an air cavity layer filled with the dry exhaled breath (DEB) and a thin metallic layer of Au is attached on the top surface. Hence, the proposed sensor is configured as, [prism/Au/air cavity/(GaN/SiO2)10]. The transfer matrix method and the Drude model are adopted to calculate the numerical simulations and reflection spectra of the design. The essential key for sensing isoprene levels is the resonant optical Tamm plasmon (TP) states within the photonic bandgap. The obtained numerical results are promising such as high sensitivity (S) of 0.321 nm/ppm or 278720 nm/RIU. This technique can be reducing the risk of infection during the taking of blood samples by syringe. Also, it can prevent the pain of patients. Finally, this work opens the door for the detection of many diseases by analyzing the breaths of patients based on photonic crystals.

Flow Visualization and Air Temperature Measurements in Symmetrically Heated Vertical Channels With Adiabatic Extensions

2002 ◽  
Author(s):  
Oronzio Manca ◽  
Marilena Musto ◽  
Vincenzo Naso
Keyword(s):  
Flow Visualization ◽  
Air Temperature ◽  
Process Parameters ◽  
Thermal Performance ◽  
Vertical Channel ◽  
Ambient Air ◽  
Expansion Ratio ◽  
Uniform Heat Flux ◽  
Thermal Plume ◽  
Cold Air

Air natural convection in a vertical channel-chimney system with the channel walls symmetrically heated at a uniform heat flux has been experimentally investigated. Flow visualization photographs and average air temperatures are presented. Some profiles of air temperature fluctuations are reported, which point out the fluid flow interactions in the chinmey. The flow visualization showed that the cold air inflow penetrating into the chimney affects the thermal performance of the channel. The improvement in the thermal performance of the channel determined by the chimney effect, for various values of the process parameters, has also been pointed out. In all investigated configurations and ranges of the process parameters the air flow in the channel was laminar. The flow in the chimney is strongly affected by the aspect ratio. Moreover, at the lower values of the expansion ratio the flow was laminar in the chimney and in its lower corner a stable vortex was noticed whereas at larger values of the expansion ratio a cold ambient air downflow worsened the thermal performance of the system. Interactions between the thermal plume arising from the channel, the vortex in the comer in the inlet chimney region and the cold air inflow yield fluctuations in the air temperature in the system. The distribution of time averaged air temperature in the cross sections validates indications given by the flow visualization in the chimney.

Numerical Analysis on the Effect of Thermal Insulation of Closure on Fire Smoke Spread Rate in Building's Corridor

2014 ◽  
Vol 513-517 ◽  
pp. 2635-2638
Author(s):  
Xuan Wei Peng
Keyword(s):  
Numerical Analysis ◽  
Thermal Insulation ◽  
Air Temperature ◽  
Spread Rate ◽  
Smoke Flow ◽  
External Insulation ◽  
Flow Prediction ◽  
Smoke Spread ◽  
Fire Smoke ◽  
Fire Ignition

The corridor is an important way of evacuation and rescue in building fire. The fire smoke flow prediction software developed successfully was applied to simulate a building with a 28.8 meters long corridor to investigate the effect of the different thermal insulation on fire smoke spread rate. Two representative thermal insulation, external insulation and internal insulation were compared. In 3600s fire time, air temperature in the corridor of external insulation is much lower than that of internal insulation. The air temperature gap gets narrowed between the two insulation methods in the corridor with the prolongation of fire time. Temperature difference increases as the distance increase from the fire ignition place. The corridor gets unsafe of internal insulation in 7 minute since fire ignition, while about half the length of the corridor stay secure of external insulation in 10 minutes since fire ignition. That implies more available safe egress time can be gained with external insulation than internal insulation. Smoke spread rate was numerically compared based on the air temperature variation. Smoke spread rate of internal insulation is much higher than that of external insulation and the corresponding ratio is 1.732:1.

scholarly journals The impact of sustainability on fire safety

2021 ◽  
Author(s):  
◽  
Mohammad Musa Al-Janabi
Keyword(s):  
Fire Safety ◽  
Sensitivity Study ◽  
Mitigation Measures ◽  
Fire Dynamics ◽  
Fire Event ◽  
Use Of Resources ◽  
Smoke Spread ◽  
Double Skin ◽  
The Impact ◽  
Small Models

<p>There is a growing demand for building green buildings that are perceived to have benefits environmentally through promoting recycling, energy efficiency and efficient use of resources. The green movement has also led to innovative technologies that are focused on reducing cost. However, the fire safety industry has concerns with the use of certain technologies that create passages for smoke and fire to spread such as passive ventilation or materials that can burn severely and release large amount of toxins. The benefit of this research is to determine which features are high risk and are commonly used. The aim of this research is to investigate whether sustainable or green features have an influence on fire safety in commercial buildings and determine which feature or features would have the most significant implications for building safety in regards to tenability. A detailed investigation was done on passive ventilation such as double skin facade and the thesis also briefly discusses other green features and their implications. There were two methods used to collect data. The first was a qualitative study done through sending out surveys to fire engineers to rate and rank the most significant features that have negative implications for fire safety in reference to the New Zealand Building Code Fire Safety Section criteria and objectives. Then, a one hour interview was carried out to determine the reason behind the engineers’ choice and their perceptions. The results from the surveys and the interviews were that double skin facade and atrium were ranked the most significant. The surveys established double skin facade has the highest ranking in terms of the worst feature, and the fire engineers reinforced that double skin facade needs to be studied as there is not enough research that have gone into this feature. While atrium issues are known and mitigation measures are well developed. A subsequent analysis for only double skin facade is conducted using Fire Dynamics Simulator (FDS) because little literature is found in regards to fire safety and double skin facade. FDS was used to simulate 14 small models and 2 large models for the best and worst scenarios of DSF. Each of the 14 models, one to three parameters are changed as part of the sensitivity study to determine which parameter have the most and least effect on fire safety in term of Carbon Monoxide (CO) and visibility. The issues the engineers raised and the mitigation measures were modelled, because the engineers had stated their opinions not facts. The output results from FDS illustrated that it is essential that the system shuts off in a fire event to prevent smoke spread to upper floors, which is the same mitigation measure that were emphasised at the interviews.</p>

Experimental Studies on Fire Spread Over Glass Fac¸ade

2010 ◽  
Author(s):  
C. L. Chow ◽  
W. K. Chow
Keyword(s):  
Southern China ◽  
Experimental Studies ◽  
Fire Spread ◽  
Glass Pane ◽  
Air Supply ◽  
Smoke Spread ◽  
Upper Level ◽  
Set Up ◽  
Fire Flame ◽  
Real Scale

There are concerns on the behaviour of glass fac¸ade under a big fire. Real-scale experiments on a single-skin fac¸ade were carried out at a large laboratory of a sizable aluminum manufacturing plant in Southern China. Burning behaviour of a three-storey high single-skin glass fac¸ade with double glazing due to an adjacent big room fire was studied. Part of the fac¸ade of width 12 m and height 13 m was installed in a testing tower. A glass pane of the fac¸ade was taken out with a model fire chamber placed next to the opening. Flashover in the chamber was set up by burning a 2 MW gasoline fire. Flame and smoke spread from the chamber would move up along the glass fac¸ade. Air temperature outside the glazing above the fire chamber was measured. It is observed that flame spread out of the opening will be attached to the upper levels. The glass fac¸ade at that level will be heated up and broken. Flame can spread to the room at the upper level. Another flashover fire will then occur with adequate air supply. This scenario on having a post-flashover fire in an adjacent upper room should be included in hazard assessment in buildings with glass fac¸ade.

scholarly journals Sound absorption properties of multi-layer structural composite materials based on waste corn husk fibers

2020 ◽  
Vol 15 ◽  
pp. 155892502091086
Author(s):  
Lihua Lyu ◽  
Jing Lu ◽  
Jing Guo ◽  
Yongfang Qian ◽  
Hong Li ◽  
...  
Keyword(s):  
Composite Materials ◽  
Absorption Coefficient ◽  
Sound Absorption ◽  
Low Frequency ◽  
Sound Absorption Coefficient ◽  
Absorption Properties ◽  
Cavity Depth ◽  
Air Cavity ◽  
Corn Husk ◽  
Structural Composite

In order to find a reasonable way to use the waste corn husk, waste degummed corn husk fibers were used as reinforcing material in one type of composite material. And polylactic acid particles were used as matrix material. The composite materials were prepared by mixing and hot-pressing process, and they were processed into the micro-slit panel. Then, the multi-layer structural sound absorption composite materials were prepared sequentially by micro-slit panel, air cavity, and flax felt. Finally, the sound absorption properties of the multi-layer structural composite materials were studied by changing flax felt thickness, air cavity depth, slit rate, and thickness of micro-slit panel. As the flax felt thickness varied from 0 to 10 mm in 5 mm increments, the peak of sound absorption coefficient shifted to low frequency. The sound absorption coefficient in the low frequency was improved with the air cavity depth varied from 0 to 10 mm in 5 mm increments. With the slit rate increased from 3% to 7% in 2% increments, the peak of sound absorption coefficient shifted to high frequency. With the thickness of micro-slit panel increased from 2 to 6 mm in 2 mm increments, the sound absorption bandwidth was broaden, and the peak of sound absorption coefficient was increased and shifted to low frequency. Results showed that the highest sound absorption coefficient of the multi-layer structural composite materials was about 1 under the optimal process conditions.

Forecasting Daily Graphs Active Energy Consumption of a Megapolis Taking Into Account Forecast Data of Daylight Illumination

2020 ◽  
Vol 63 (5) ◽  
pp. 67-71
Author(s):  
Svetlana Vyalkova ◽  
◽  
Ivan Nadtoka ◽  
Keyword(s):  
Mathematical Model ◽  
Time Series ◽  
Spectral Analysis ◽  
Air Temperature ◽  
Meteorological Factors ◽  
Active Power ◽  
Natural Illumination ◽  
One Dimensional ◽  
Singular Spectral Analysis ◽  
Analysis Of Time Series

The results are presented of the analysis of the daily average values graphs for the time series of active power, air temperature, natural illumination, cloudiness and precipitation for Moscow. The method of one-dimensional singular spectral analysis were obtained the results of the dependence of active power on air temperature and natural illumination and the dependence of active power on cloudiness, precipitation and illumination. Mathematical model was proposed of one-dimensional singular spectral analysis of time series of natural illumination, cloudiness and precipitation is proposed to improve the results of forecasting active power. The results are presented of the decomposition of active power and meteorological factors for 2019 year. To implement the mathematical model of one-dimensional singular spectral analysis of time series of active power and meteorological factors was used the developed algorithm in the R- software Studio in language R. Forecasts daily graphs of active power were made using predictive data of natural illumination obtained using a forecast model based on a neural network during February 2019.The proposed version of the one-dimensional singular spectral decomposition allows finding the relationship between the selected harmonic components of power consumption and natural illumination and power consumption and air temperature. For analyzing and transforming the time series of meteorological factors were used the data of the meteorological hardware-software complex PAC "Meteo".

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