Why are cooktop fires so hazardous?

Direct numerical simulation of DME auto-ignition with temperature and composition stratification under HCCI engine conditions

Radiant, convective and heat release characterization of vegetation fire

This study validates numerical models for mixed polymer combustion in a B-707 aircraft cargo compartment against Federal Aviation Administration test data. A simplified approach using a predefined mass loss rate was compared with a detailed model coupling in-depth heat transfer and pyrolysis kinetics based on the assumption of negligible co-pyrolysis effects. Both approaches reliably captured smoke dynamics and light transmission. The detailed model predicted the mass loss rate with high accuracy, matching the experimental value of 0.11 g/s at 200 s after the ignition. However, it significantly overpredicted the heat release rate with a peak value of 8 kW versus 5 kW in the experiment. This discrepancy was examined through a sensitivity analysis of key parameters: the radiative fraction, heat of combustion, turbulence model, and pyrolysis kinetics. The Smagorinsky model best captures the growth pattern of the heat release and mass loss rates, despite its larger deviation from the experimental data compared to other models. The analysis revealed that the radiative fraction and the activation energy of high heat-of-combustion materials like high-density polyethylene are the most influential parameters. One possible solution to the overestimation is the calibration of the activation energy and heat of combustion values for high-energy materials like HDPE. The results confirm the detailed model’s physical realism for fire spread modeling and highlight a path for improving its heat release rate predictions. Further investigation is required across a wider range of computational cases with varying sample mass fractions, compositions, geometries, and boundary conditions to establish the broader applicability of this approach.

A series of experiments was conducted to investigate the global preignition and combustion characteristics of corn oil heated in 9.7 to 26 cm diameter pans by a residential electric-coil element cooktop. For comparison, torch-ignited gasoline, heptane, and corn oil experiments were conducted in the same configuration except without the heating element energized. Heating oil on a typical electric cooktop leads to vaporization and generation of an aerosol cloud followed by autoignition. The evolution of the light-extinction coefficient before autoignition is measured and shown to be related to the pan diameter and initial fuel mass. Continued heating leads to enhanced vaporization of the burning oil and growing fires with the peak heat release rate, radiative heat flux, radiative fraction, and peak flame height larger than the gasoline fires regardless of pan diameter. CO and soot yields, and the CO/CO2 ratio are measured to decrease with pan diameter.

Heating oils and fats for a considerable length of time results in chemical reactions, leading to the aggravation of a free radical processes, which ultimately contributes to atherosclerosis. Our study focused on elucidating the effect of feeding heated oils with or without dietary cholesterol on the development of atherosclerosis in rabbits. We heated palm olein and corn oil at 180 °C for 18 h and 9 h per day, respectively, for two consecutive days. Next, 20 male rabbits were divided into four groups and fed the following diet for 12 weeks: (i) heated palm olein (HPO); (ii) HPO with cholesterol (HPOC); (iii) heated corn oil (HCO); and (iv) HCO with cholesterol (HCOC). Plasma total cholesterol (TC) was significantly lower in the HCO group compared to the HCOC group. Atherosclerotic lesion scores for both fatty plaques and fatty streaks were significantly higher in the HCO and HCOC groups as compared to the HPO and HPOC groups. Additionally, fibrous plaque scores were also higher in the HCO and HCOC groups as compared to the HPO and HPOC groups. These results suggest that heated palm oil confers protection against the onset of atherosclerosis compared to heated polyunsaturated oils in a rabbit model.

With the depletion of gas reserves, the increase in commercial demand and the rising cost of natural gas, alternatives for a reliable, safe, economical and efficient method for preheating produced fluids in heater treaters is sought. A case history on the performance of an electric immersion heater versus a conventional gas firetube is presented under similar pumping and climatic conditions. The immersion heater uses the principle of resistive type of heating (thermal energy). Some advantages of using electric immersion heater's are: They help reduce the possibility of fire or explosion hazards since there are no open flames. Explosion-proof units are available if required.They eliminate all inconveniences created by the pilot light blowing out in a gas-fired vessel thus requiring the fluid to be rerun through the treater.By the removal of selected in-line fuses, the quantity of heat can easily be adjusted to the requirement of the job (from the minimum to maximum unit capacity), giving a flexibility that cannot be obtained from the gas fired unit.Existing gas-fired heater treaters can be easily retrofitted with an electric immersion heater. The test showed the cost of electric heating to be directly competitive with the cost of gas treating in one of Amoco's operated West Texas fields. In areas where residue gas is sold for a higher price (over $0.50 per MCF), the fuel cost difference might strongly favor the electric heating element. The heating element would have immediate application in areas where treater gas has to be purchased from a utility or is not available at all, and in areas where it is impossible or undesirable to make daily checks of gas-fired treaters.

A series of experiments were conducted in order to determine the global combustion behavior of a number of liquid fuels burning in large (1 MW to 3 MW) spray fires in an open environment. The experiments described here provide a characterization of the global fire characteristic of the liquid spray burner, which is a standard fixture in the NIST Large Fire Laboratory. The fuels tested include n-heptane, toluene, a commercial blend of heptane isomers, Jet A, and a heptane/toluene fuel mixture. The fuel flow was controlled. Measurements were made of the radiative emission to the surroundings, the heat release rate, and the emission of soot, CO 2 , and CO. These measurements were normalized by the mass burning rate to determine the radiative heat loss fraction, the combustion efficiency, and the yields of soot, CO 2 , and CO.

Experimental study on the variation regimes of window ejecting flame height

Buoyant turbulent diffusion flame heights of free-, wall- and corner air entrainment conditions: Experiments and global model based on mirror approach

Flammability and thermal stability studies of styrene–butyl acrylate copolymer/graphite oxide nanocomposite

Consumption of corn oil for cooking purpose is gaining popularity. The present study examined the effect of heated corn oil on blood pressure and its possible mechanism in experimental rats. Thirty male Sprague-Dawley rats were randomly divided into 5 groups and were fed with the following diets, Group I was fed with basal diet only; whereas group II,III,IV and V were fed with basal diet fortified with 15% (w/w) either fresh, once-heated, five-timesheated or ten-times-heated corn oil, respectively for 16 weeks. Body weight, blood pressure were measured at baseline and weekly interval for 16 weeks. Inflammatory biomarkers which included soluble intracellular adhesion molecules (sICAM), soluble vascular adhesion molecules (sVCAM) and C reactive protein (CRP), were measured at baseline and the end of 16 weeks. The rats were sacrificed and thoracic aorta was taken for measurement of vascular reactivity. There was significant increase in the blood pressure in the groups fed with heated once, five-times (5HCO) and ten-timesheated corn oil (10-HCO) compared to the control. The increase in the blood pressure was associated with an increase in CRP, sICAM and sVCAM, reduction in vasodilatation response to acetylcholine and greater vasoconstriction response to phenylephrine. The results suggest that repeatedly heated corn oil causes elevation in blood pressure, vascular inflammation which impairs vascular reactivity thereby predisposing to hypertension. There is a need to educate people not to consume corn oil in a heated state.

Analysis of the Combustion Efficiencies and Heat Release Rates of Pool Fires in Ceiling Vented Compartments

Ni–Fe layered double hydroxide/graphene hybrids were synthesized by a one-pot in situ solvothermal route. X-ray diffraction and X-ray photoelectron spectroscopy analyses showed that the formation of Ni–Fe layered double hydroxide (Ni–Fe LDH) and the reduction of graphene oxide occurred simultaneously during the one-pot solvothermal process. TGA results showed that the incorporation of Ni–Fe LDH significantly improved the thermal stability of the graphene. Subsequently, Ni–Fe LDH/graphene hybrids were introduced into epoxy resins for reducing their fire hazard. With the incorporation of 2.0 wt% of Ni–Fe LDH/graphene, the onset thermal degradation temperature of the epoxy composite was significantly increased by 25 °C compared to that of pure epoxy. Also, the addition of Ni–Fe LDH/graphene hybrids imparted excellent flame retardant properties to the epoxy matrix, evidenced by the dramatically reduced peak heat release rate and total heat release values obtained from a micro combustion calorimeter and cone calorimeter. This dramatically reduced fire hazard was mainly attributed to the synergistic effects of Ni–Fe LDH/graphene hybrids: the adsorption and barrier effect of graphene slowed down the thermal degradation of the polymer matrix, inhibited the heat and flammable gas release and promoted the formation of graphitized carbons, while Ni–Fe LDH improved the thermal oxidative resistance of the char layer.

A series of flame‐retardant rigid polyurethane foams (RPUFs) containing dimethyl methylphosphonate (DMMP) and expandable graphite (EG) were prepared by box‐foaming. The RPUFs were characterized by thermogravimetric analysis (TGA), the limiting oxygen index (LOI), cone calorimeter, and scanning electron microscope (SEM). The decomposition process of DMMP was investigated by Pyrolysis‐Gas Chromatography/Mass Spectroscopy (Py‐GC/MS). Accordingly, their flame retardant behaviors and mechanism were also discussed. The results show that the DMMP/EG system can linearly enhance the LOI value from 19.2% of the pure RPUF to 33.0% of RPUFs containing 16 wt% flame retardant. In addition, the DMMP/EG system also remarkably increases yields of the residual char and drastically decreases the peak value of heat release rate (PHRR), heat release rate (HRR), total heat release (THR), total smoke release (TSR), and the yields of CO (COY). In the flame retardant RPUFs, when the matrix is ignited, the flame retardant DMMP should be decomposed to gaseous PO2 fragments, which can inhibit free radical chain reaction of flammable alkyl free radical from the decomposed matrix; whereas the flame retardant EG can rapidly expand and form loose and worm‐like expanding graphite char layer accordingly, which can hinder the heat transmission to the inner matrix and reduce decomposing velocity of matrix. After the combination of the two flame retardant effects, the DMMP/EG flame retardant system provides the matrix with better flame retardant effects than one of them does. Namely, it shows excellent gas‐condensed bi‐phase synergistic effect. POLYM. COMPOS., 35:301–309, 2014. © 2013 Society of Plastics Engineers

최근 지하공동구(Underground Common Utility Tunnels)는 도시민이 일상생활을 영위하는데 필요한 전기, 통신, 상수도, 도시 가스, 하수도뿐만 아니라 냉난방시설, 진공 집진관, 정보처리케이블 등의 시설물을 2종 이상 공동으로 수용하기 위한 지하시설물로서 국가의 중추기능을 담당하는 시설이지만, 화재 사고시 신속한 대처가 힘들고 각종 케이블 연소시 발생하는 유독가스 및 연기에 의해 공동구 내에 진입하여 진압하기가 힘들다. 따라서 화재발생시 막대한 재산피해 및 통신두절 등 국가의 중추신경이 마비됨은 물론 시민불편사항을 초래하게 된다. 따라서 본 논문은 지금까지 발생 되어온 국내,외 공동구 화재사례에서 화재발생의 주요원인으로 전기공사로 인한 합선 및 가연성케이블에 의한 열화접촉으로 화재가 발생하는 것이 대다수를 차지하고 있음에 착안하여 실제 공동구 모형을 제작하고 화재를 재현함으로서 과학적으로 화재의 성상을 분석하는데 그 목적이 있다. 화재실험은 지하공동구 내에 정온식 감지선형 감지기(Line type fixed temperature detector), 방화문(Fire door), 연결살수설비(Connection deluge set), 및 환기설비를 설치하고, 송 배전케이블은 일정구간 내화(Fireproof)도료로 도장하며, 난방관은 내화 피복된 상태에서 실험하였다. 그 결과 Type II의 경우 최고온도가 <TEX>$932^{\circ}C$</TEX>로 측정되었고, 일정한 온도에서 정온식감지선형감지기가 화재위치를 정확하게 수신반에 표시되었다. 그리고 Type III의 경우인 송 배전케이블은 일정구간 내화도료로 도장한 것은 내화성능이 없는 것으로 나타났고, 내화피복(Fireproof covered)된 난방관은 약 30분 정도의 내화성능이 있는 것으로 나타났다. 또한 화재뮬레이션 결과는 실물화재시험시의 화재하중(Fire load)을 입력하여 실시한 결과로서 최고온도가 <TEX>$943^{\circ}C$</TEX>로 실물화재실험시의 <TEX>$932^{\circ}C$</TEX>와 거의 일치 하였다. 따라서 공동구 화재하중만으로 화재시뮬레이션을 실시하여 화재성상에 대한 예측이 가능한 것으로 판단되며 시뮬레이션으로 얻은 열방출률(Heat release rate), 연기층의 높이, 산소(O2), 일산화탄소(CO), 이산화탄소(CO2)의 농도 등의 결과 값들은 실제 화재실험시의 값으로 적용시킬 수 있는 것으로 판단된다. 향후 본 연구에서 구축한 국내 지하공동구 화재사고에 대한 실험자료 및 매년 지속적으로 화재사례들을 분석하여 축적하고 법 규정 및 관리 메뉴얼 등을 보완함으로써 국내 지하공동구 화재사고에 대한 보다 신뢰성 있는 정보를 제공해 줄 수 있을 것이며, 효과적이고 체계적으로 지하공동구의 신설 및 유지 관리 보수에 기여할 것으로 기대된다. Recent underground common utility tunnels are underground facilities for jointly accommodating more than 2 kinds of air-conditioning and heating facilities, vacuum dust collector, information processing cables as well as electricity, telecommunications, waterworks, city gas, sewerage system required when citizens live their daily lives and facilities responsible for the central function of the country but it is difficult to cope with fire accidents quickly and hard to enter into common utility tunnels to extinguish a fire due to toxic gases and smoke generated when various cables are burnt. Thus, in the event of a fire, not only the nerve center of the country is paralyzed such as significant property damage and loss of communication etc. but citizen inconveniences are caused. Therefore, noticing that most fires break out by a short circuit due to electrical works and degradation contact due to combustible cables as the main causes of fires in domestic and foreign common utility tunnels fire cases that have occurred so far, the purpose of this paper is to scientifically analyze the behavior of a fire by producing the model of actual common utility tunnels and reproducing the fire. A fire experiment was conducted in a state that line type fixed temperature detector, fire door, connection deluge set and ventilation equipment are installed in underground common utility tunnels and transmission power distribution cables are coated with fire proof paints in a certain section and heating pipes are fire proof covered. As a result, in the case of Type II, the maximum temperature was measured as <TEX>$932^{\circ}C$</TEX> and line type fixed temperature detector displayed the fire location exactly in the receiver at a constant temperature. And transmission power distribution cables painted with fire proof paints in a certain section, the case of Type III, were found not to be fire resistant and fire proof covered heating pipes to be fire resistant for about 30 minutes. Also, fire simulation was carried out by entering fire load during a real fire test and as a result, the maximum temperature is <TEX>$943^{\circ}C$</TEX>, almost identical with <TEX>$932^{\circ}C$</TEX> during a real fire test. Therefore, it is considered that fire behaviour can be predicted by conducting fire simulation only with common utility tunnels fire load and result values of heat release rate, height of the smoke layer, concentration of O2, CO, CO2 etc. obtained by simulation are determined to be applied as the values during a real fire experiment. In the future, it is expected that more reliable information on domestic underground common utility tunnels fire accidents can be provided and it will contribute to construction and maintenance repair effectively and systematically by analyzing and accumulating experimental data on domestic underground common utility tunnels fire accidents built in this study and fire cases continuously every year and complementing laws and regulations and administration manuals etc.