Investigation of spontaneous combustion tendency of vegetable oils by the means of differential thermal analysis

The potential of vegetable oils to undergo violent thermal oxidation is long-known problem. The process of this oxidation is investigated by the means of differential thermal analysis. Polyurethane foam was saturated with Tung oil rich in unsaturated fatty acids at three different mass rations, and airfl ow at three different rates is introduces to the sample to ensure suffi cient volume of air for oxidation. The samples were thermally stressed both dynamically and isothermally. The results were compared to results of standard differential Mackey test

Učinak toplinske obrade na proces izgaranja drva smreke (Picea abies)

This paper deals with the effect of thermal treatment of spruce wood on its burning process. Samples of 100 mm x 100 mm were dried out and then heat-treated at 150 °C, 200 °C, 250 °C and 300 °C. Thus prepared samples were tested on a cone calorimeter at a heat flow of 50 kW·m-2. The obtained results clearly show that with the increasing temperature of the treatment, the released heat from the surface unit decreases and the unit weight increases. The carbon dioxide concentration in the flue gas increases as well, however, the optical density of the smoke decreases substantially. It can be stated that the burning of spruce wood is considerably affected mainly by the thermal treatment at temperatures above 200 °C. From the point of view of the use of spruce wood as fuel, the most optimal treatment temperature is 250 °C.U radu se razmatra učinak toplinske obrade smrekova drva na proces njegova gorenja. Uzorci dimenzija 100 x 100 mm osušeni su i zatim toplinski obrađeni na 150, 200, 250 i 300 °C. Tako pripremljeni uzorci ispitani su na konusnom kalorimetru, pri toplinskom toku od 50 kW·m-2. Iz dobivenih se rezultata može uočiti da se povećanjem temperature toplinske obrade smanjuje oslobođena toplina površinske jedinice i povećava jedinična težina uzoraka od smrekovine. Koncentracija ugljikova dioksida u dimnom plinu također se povećava, ali se optička gustoća dima znatno smanjuje. Može se također zaključiti da na izgaranje smrekovine uglavnom znatno utječe toplinska obrada pri temperaturama višim od 200 °C. S gledišta upotrebe smrekovine kao ogrjeva, optimalna je temperatura toplinske obrade tog drva 250 °C

A new approach to the assessment of the reduction in visibility caused by fires of electrical cables

Electricity is the most important form of household energy and one of the most important forms of energy for industry and transport. Electrical distribution in construction and transport is almost exclusively implemented using electrical cables. One of the unresolved problems associated with electrical cables is the release of smoke and the resulting reduction of visibility in case of fire in the area. In this study, a new approach was developed to assess the reduction of visibility in an area affected by an electrical cable fire. This approach is based on the determination of the critical ratio of smoke volume (in the smoke layer and exhausted from the fire compartment) to the length of the burning cable, through which the visibility of reflective and illuminated signs was reduced to a lower limit value (a standard of 10 m). The input data for this approach was the extinction area of the smoke released from one meter of burning cable and the length of the cables in the area. This approach was used to test two power cables (CHKE-V J3x1.5 and CHKE-R J3x1.5) and one signal cable J-H(St)H 1 x 2 x 0.8 with the B2(ca), s1, d1, a1 fire reaction class. The smoke extinction area of the examined cables was determined using a cone calorimeter at a heat flux of 50 kW/m(2). The obtained data showed that in order to maintain a visibility of 10 m for reflective signs, the critical ratio of smoke volume to length of burning cable was 7.5 m(3)/m. For illuminated signs, the critical ratio was 2.8 m(3)/m. The relationship between burning length and visibility allows the calculation of visibility in the fire compartment affected by cable fire only from cables length.Web of Science53art. no. 4

Použitie octree štruktúry na urýchlenie metódy ray tracing

Niekteré spôsoby urýchlenia metódy ray tracing využívajú priestorové rozdelnie scény a jej reprezentáciu pomocou octree štruktúry. Hlavné problémy spojené s použitím octree sú: vhodná reprezentácia, efektivny spôsob vytvorenia (rozdelenia scény na kocky octree) a rýchly "prechod" sledovaného lúča cez štruktúru. V článku sú stručne popísané niektoré pristupy k riešeniu týchto problémov

Použitie octree struktury na urychlenie metody ray tracing

Niektoré spôsoby urychlenia metody ray tracing využivajú priestorové rozdelenie scény a jej reprezentáciu pomocou octree štruktúry. Hlavné problémy spojené s použitím uctree sú: vhodná reprezentácia, efektivny spósob vytvorenia (rozdelenia scény na kocky octree) a rychly "prechod" stedovaného lúča cez štruktúru. V článku sú stručne popisané niektoré prístupy k riešeniu týchto problémov

A New Approach to the Assessment of the Reduction in Visibility Caused by Fires of Electrical Cables

Electricity is the most important form of household energy and one of the most important forms of energy for industry and transport. Electrical distribution in construction and transport is almost exclusively implemented using electrical cables. One of the unresolved problems associated with electrical cables is the release of smoke and the resulting reduction of visibility in case of fire in the area. In this study, a new approach was developed to assess the reduction of visibility in an area affected by an electrical cable fire. This approach is based on the determination of the critical ratio of smoke volume (in the smoke layer and exhausted from the fire compartment) to the length of the burning cable, through which the visibility of reflective and illuminated signs was reduced to a lower limit value (a standard of 10 m). The input data for this approach was the extinction area of the smoke released from one meter of burning cable and the length of the cables in the area. This approach was used to test two power cables (CHKE-V J3x1.5 and CHKE-R J3x1.5) and one signal cable J-H(St)H 1 × 2 × 0.8 with the B2ca, s1, d1, a1 fire reaction class. The smoke extinction area of the examined cables was determined using a cone calorimeter at a heat flux of 50 kW/m2. The obtained data showed that in order to maintain a visibility of 10 m for reflective signs, the critical ratio of smoke volume to length of burning cable was 7.5 m3/m. For illuminated signs, the critical ratio was 2.8 m3/m. The relationship between burning length and visibility allows the calculation of visibility in the fire compartment affected by cable fire only from cables length

The effect of air flow rate on smoke stratification in longitudinal tunnel ventilation

The construction of tunnels is associated with mining. For safety and suitable working conditions, it is necessary to ensure that there is suitable ventilation during construction. During operation, tunnels form the infrastructure of the area, which has a number of characteristics. Tunnel ventilation is designed with regards to many different factors. Longitudinal ventilation is especially used in one-way, extra-urban tunnels but in some cases also in urban or two-way tunnels. The article describes the purpose and types of tunnel ventilation, focusing on longitudinal ventilation and ventilation design strategy. Longitudinal tunnel ventilation is the cause of significant turbulence that affects the smoke stratification. The article compares different tunnel ventilation options in terms of selected strategies and the different values of applied airflow rates. A case study was conducted on the Klimkovice road tunnel in the Czech Republic using the fire model from the Fire Dynamics Simulator. The study compares the effect of airflow rate on smoke stratification. The study was conducted with air flow rate values of 0 to 5 m.s-1. The results of the study show that even with lower airflow rates, the smoke build-up is so significant that the safety of individuals in the tunnel cannot be ensured. The dynamicity of fire is also an important factor. Opting for a lower airflow rate strategy because of higher expected congestion or other factors is a questionable practice. Greater airflow rates, however, create better conditions for evacuating individuals, although it is also necessary to combine smoke stratification options with the selected ventilation strategy.Web of Science24318717

The Influence of Heat Flux on the Ignition of OSB Boards

Príspevok sa zaoberá štúdiom vplyvu tepelného toku na zápalnosť OSB dosiek vybraných hrúbok. Pri posudzovaní nebezpečenstva požiaru treba brať do úvahy schopnosť materiálu zapáliť sa pri vonkajšom pôsobení iniciačného zdroja - zápalnosť. Je charakterizovaná časom vznietenia dosiek, ktoré boli vystavené zvolenej úrovni hustoty tepelného toku (43 až 50) kW.m-2. Meraním bol stanovený exponenciálny model závislosti času vznietenia OSB dosiek od hustoty tepelného toku.The article deals with experimental determination the influence of heat flow on OSB board ignition time. There was determined ignition time for heat flow from (43 to 50) kW.m-2. There was determined exponential model dependence of ignition time of OSB board on heat flow based on measured values